BRITISH ANTARCTIC EXPEDITION 1907-9 UNDER THE COMMAND OF SIR E.H. SHACKLETON,C.V.O. REPORTS ON THE SCIENTIFIC INVESTIGATIONS GEOLOGY VOL. L HORS Dies PEO RIE FOR EDVCATION FOR SCIENCE LIBRARY OF THE AMERICAN MUSEUM OF NATURAL HISTORY BRITISH ANTARCTIC EXPEDITION 1907-9 UNDER THE COMMAND OF SIR E. H. SHACKLETON, C.V.O. REPORTS ON THE SCIENTIFIC INVESTIGATIONS GH OL, O-G Y Vou. I. GEOLOGY To be published later, will contain Papers by the following authors on the Petrology of the rocks collected by the Expedition : THE LIMESTONES OF SOUTH VICTORIA LAND Proressor E. W. SKEATS, D.Sc. THE ALKALINE ROCKS OF ROSS ISLAND H. I. JENSEN, D.Sc. THE ROCKS OF THE NORTH COAST OF VICTORIA LAND DOUGLAS MAWSON, D.Sc. THE DOLERITES OF SOUTH VICTORIA LAND W. N. BENSON, B.Sc. NOTES ON SOME ERRATICS COLLECTED AT CAPE ROYDS W. G. WOOLNOUGH, D.Sc. THE PYROXENE GRANULITES OF VICTORIA LAND A. B. WALKOM, B.Sc. NOTES ON SOME ROCKS LEFT AT DEPOT ISLAND LEO A. COTTON, B.A., B.Sc. INCLUSIONS IN THE VOLCANIC ROCKS OF ROSS ISLAND J. ALLAN THOMSON, D.Sc. MEASUREMENTS OF SOME #GIRINE CRYSTALS FROM ROSS ISLAND Miss F. COHEN, B.A., B.Sc. Also Papers on the Fossils collected by the Expedition : FORAMINIFERA AND OSTRACODA FROM UPTHRUST MARINE MUDS FREDERICK CHAPMAN, M.A. REDENT SHELLS FROM UPTHRUST MARINE MUDS AND RAISED BEACHES C. E. HEDLEY, M.A., F.L.S. PLATE I MOUNT EREBUS AND THE FOOTHILLS IN THE NEIGHBOURHOOD OF THE WINTER QUARTERS | Frontispiece BRITISH ANTARCTIC EXPEDITION 1907-9 UNDER THE COMMAND OF SIR E. H. SHACKLETON, C.V.O. REPORTS ON THE SCIENTIFIC INVESTIGATIONS GHOLOGY VOL. I GLACIOLOGY, PHYSIOGRAPHY, STRATIGRAPHY, AND TECTONIC GEOLOGY OF SOUTH VICTORIA LAND BY PROFESSOR T. W. EDGEWORTH DAVID, C.M.G., F.R.S., M.A., Hon. D.Sc.(Oxon.) AND RAYMOND E. PRIESTLEY, F.G:S. WITH SHORT NOTES ON PALAZONTOLOGY BY T. GRIFFITH TAYLOR, B.A., B.E., B.Sc, AND PROFESSOR E. J. GODDARD, D.Sc. (WITH 95 PLATES AND 67 FIGURES IN THE TEXT LONDON PUBLISHED FOR THE EXPEDITION BY WILLIAM HEINEMANN 21 BEDFORD STREET, W.C. 1914 USCC RUE i Se PAD ECAC | 33-2 oir Soph — PRINTED AT THE BALLANTYNE PRESS LONDON TO SIR JAMES KEY CAIRD, BART. IN GRATEFUL ACKNOWLEDGMENT OF HIS GENEROUS SUPPORT OF THE IMPERIAL TRANSANTARCTIC EXPEDITION AND IN RECOGNITION OF HIS KEEN INTEREST IN ALL SCIENCE PREFACE A DISTINGUISHED Norwegian geologist has remarked : * “ While we know fairly well the effect of running water from glaciated lands with a wet climate, we practically do not know anything of the way in which a continuous ice covering pure and simple may sculpture a land.” Herein lies one of the many charms of that great white con- tinent—so vast that even where narrowest it would stretch from Calais to the Caspian —viz. that its ice covering, except for the Antarctic Horst in the Ross Sea region, is nearly continuous. One might, therefore, imagine that in Antarctica Reusch’s ideal is at present realised ; and so it is, but to a comparatively limited extent. Man has arrived in Antarctica too late, just as civilised man has been in Europe too late, bas gone to North America too late, and still goes to Greenland and Spitzbergen too late, to observe anything like the full effect of a continuous ice covering in sculpturing land. Probably everywhere to-day the ice-fields of the world are on the wane, in spite of what appear to be exceptions in the case of local advancing glaciers. De Geer has suggested that ice does not necessarily flow evenly and steadily, as water does, but is subject probably to intermittent outrushes followed by short epochs of retreat. These outrushes may be due to prolonged accumulation of inland ice setting up a critical pressure ultimately sufficient to overcome frictional resistance and resistance to shearing. The ice then moves away rapidly towards lower levels, and in polar regions thrusts itself into the sea, and across the sea-floor, until its seaward edge floats and breaks away as bergs. Such an epoch of activity may be followed by a resting stage, when ablation of ice, partly through the breaking away of bergs, partly through thaw and evaporation, exceeds what is added through ice flow and snow precipitation. Thus in one and the same district one glacier may be rapidly advancing while an adjacent glacier is retreating, as is the case in Spitzbergen with the Sefstrém Glacier and the Von Post Glacier respectively.f With the exception of such glaciers as are in a stage of temporary advance all the ice masses in the world are probably dwindling. Certainly the Antarctic ice sheet is decreasing rapidly, and this ice shrinkage has been general, as far as we know, over the whole area of the Antarctic Continent, from circle to pole. We can no more judge of the work that the Antarctic ice has accomplished by what it is accomplishing now in sculpturing the local land than we can measure the erosive action of a river when in flood by what * Congrés Geologique International, XI, Session, Stockholm, 1910. “ A Few Words on the Effects of Glacial Erosion in Norway,’ H. Reusch. + We are indebted to G. W. Lamplugh, F.R.S., for kindly calling our attention to this feature. ix b x PREFACE we know of its work when it is at its lowest level. Frequently a river alternately erodes or aggrades its course according as to whether it is in flood or at lowest level ; so that if we saw such a river at its lowest level, or at any rate during the ebbing of the flood, and noted that then it had no appreciable erosive force, we should not be justified in concluding that it had not accomplished erosion in the past. And as with water so it is with ice, with the exception of the phenomenon explained as above by De Geer. The Antarctic ice is certainly not now in flood, and its power to sculpture land is enormously diminished as compared with what it was when the outlet glaciers were about 2500 feet thicker than now, the Ross Barrier 800 feet thicker and 200 miles longer, and much of the island ice perhaps 1000 feet thicker than at present. Nevertheless there is much to learn from present Antarctic ice conditions which helps towards the interpretation of the phenomena of a past glacia- tion in Pleistocene times in both hemispheres. For example, the Ross Barrier may be compared with the North Sea ice sheet ; the glaciation of Gerlache Channel and Brans- field Strait with that of the Irish Sea and of the Isle of Man ; the upthrust marine muds on the flanks of Erebus with some of the British marine deposits pushed up from the bottom of the Irish Sea, &e. Some details of this will be given in the summary at the end of the second volume. No less entrancing than the glacial problems of Antarctica is the enigma of its lost Andes. In West Antarctica the Andean rocks, both sedimentary and eruptive, are typically developed and as typically folded, attaining heights of 6000 to 8000 feet. In East Antarctica, with the exception, perhaps, of the grano-diorites of King Edward VII. Land, Andean rocks and Andean structures are absent, but there emerges from near the South Pole a mighty block- faulted range from 8000 to 15,000 feet high, with eruptive rocks typically alkaline, and upper Palzeozoic coal measures, not folded, resting partly on Devonian, partly on Cambrian, or in places on Pre-Cambrian rocks. Have the Andean faults swerved away from the Andean fold lines and the Andean petrological belt, so as to yield a block-faulted range meeting in a sort of tectonic virgation the true Andean fold lines of West Antarctica ; or is the range of the Antarctic Horst entirely distinct from the Andes, and does it trend to Prince Regent Luitpold Land and Coats Land, on the eastern side of the Weddell Sea? If the latter view is correct, a sea channel, as suggested by Penck, may divide Antarctica into two portions, leaving Graham Land with all West Antarctica and Carmen Land and King Edward Land in the condition of a festooned archipelago. A physiographic feature of great interest in the part of Antarctica to which these notes relate is the development of an ‘‘ice divide” to the west of the Antarctic Horst of Ross Sea. Though considerably lower than the ranges of the Horst, the “ice divide” sends mighty glaciers through low gaps in the Horst eastwards to Ross Sea. Is this “ice divide” at all analogous to the Pleistocene “ice divide” of the Baltic Sea at a time when it sent ice westwards across the summit of Areskutan, 5000 feet above the level of the Baltic, across the main range of Scandinavia into the North Sea? Greenland has obviously such an ice divide at the present day. PREFACE Xl Petrologically the rocks of the Ross Sea region constitute a distinct province. The reports by our colleagues, published in the second half of this Memoir, make it clear that the region has been a province for alkaline rocks from Paleozoic time. The relation of these rocks to one another, that of the alkaline granites to the vast sills of dolerite, and the latter to the great variety of effusive rocks produced by Erebus and adjacent vol- canoes ; and the relations of the products of eruption of the smaller parasitic cones to those of the parent cones present problems of unique interest. Biologically the degla- ciated region of Cape Royds with its glacially-formed lakes has proved most interesting on account of the rich harvest of various forms of microscopic life, especially Rotifera and Tardigrada, already described by our colleague James Murray in the biological memoirs of our expedition. The occurrence of beds of algal peat on the floors of some of these lakes has furnished material for analysis and for notes given later in this volume. Palontologically Antarctica is proving a veritable treasure-house. To a lower Cambrian fauna, contained in as yet almost untouched massive limestone, must now be added the Devonian rocks, with the fossil fish plates discovered by F. Debenham and T. Griffith Taylor on Scott’s last expedition at Granite Harbour. These Old Red Sandstone fish are shortly to be described by Dr. A. S. Woodward. Most fascinating also are the many problems presented by the vastly extensive, horizontally bedded coal measures and their associated fossil flora. This great field extends certainly from at least as far south as the Beardmore Glacier, in 85° 8., to certain nunatakker recently discovered by Madigan’s party, on the Mawson Expedition, to the east of Adélie Land near the Antarctic circle, a distance of at least 1300 miles. The seven coal seams discovered by F. Wild and Sir Ernest Shackleton, together with fossil wood and rootlets, proved for the first time that the ‘‘ Beacon Sandstone” of H. T. Ferrar is a coal-bearing formation and that trees formerly flourished there, within 5° of the South Pole, in an area which is now in almost total darkness for five months in the year. As a result of a preliminary examination of the fossil plants, so heroically earried by Captain Scott and his comrades to the very end of their terrible journey, Mr. Debenham has stated * that he considers them to be of Upper Paleozoic Age. A detailed report of these plant remains is about to be published in connection with the Scientific Report of the Scott Expedition 1910-1913. So far no trace of the Jurassic strata, like those of Hope Bay, from which J. Gunnar Andersson and Dr. Nordenskjild reaped the rich harvest of fossil plants, which have been described by Nathorst, has been discovered in East Antarctica. Neither has any evidence been found there of the extensive marine cretaceous strata developed in West Antarctica at James Ross Island, Cockburn Island, and Snow Hill Island ; nor again of the Oligocene or Lower Miocene strata, like those of Seymour Island, from which Nordenskjéld obtained bones of penguin and leaves like those of Fagus and Sequoia. The Pliocene Pecten Conglomerates of Cockburn Island also appear to be wanting in East Antarctica. * “ Scott’s Last Expedition,” vol. ii. p. 437. xil PREFACE It would seem, therefore, that in East Antarctica the great ‘‘ Schild” has formed a land surface, subsequent to the extensive lower Cambrian transgression, from Devonian times down to the present. The late Cainozoic, including recent, Paleeogeography of Antarctica, based on paleontological and biological evidence, has been well summarised by C. Hedley in the “ Proceedings” of the Linnean Society, London, for 1913.* A feature of the greatest possible interest in connection with Antarctica is the recent discovery by R. C. Mossman that there is a causal connection between the state of the ice in Weddell Sea, the height of the barometer in the South Orkneys, and the rainfall in Chili and in the Parand region, together with the depth of water in the Parand River. Much ice in the Weddell Sea region appears to bring about a high barometer at the South Orkneys, and this high pressure seems to drive the rainy belts of the sub-tropics of the Southern Hemisphere nearer to the equator than usual. Thus, on Mossman’s theory, Antarctica acts meteorologically as a great tension screw. Presumably, if the alternations of relatively colder and relatively warmer conditions take place synchronously at either pole, such part of the earth’s atmosphere as lies between the polar circles is alternately compressed or expanded, with a concertina-like movement, according as to whether the area of the ice there is above or below the normal in extent. This very suggestive theory induces the hope that it may hereafter be possible, by means of the wireless station established by Dr. Mawson at Macquarie Island (subsequently taken over by the Commonwealth), to trace a connection between the state of the ice in the Ross Sea and the weather of Australasia. To complete the essential observations it would be necessary to establish a wireless meteorological station in Antarctica itself, and there can be no doubt that in course of time this will be an accomplished fact. Thus, by the increased accuracy of the weather forecasts, not only will trade and commerce be promoted, but, it is hoped, many a shipwreck averted. Surely such a result would justify all the cost, hardship, suffering, and even sacrifice of human life which recent Antarctic expeditions have involved ! It is hoped that the second volume of this memoir, with papers relating to petrology by Drs. H. I. Jensen and D. Mawson, Professor Skeats, Professor Wool- nough, Dr, Allan Thomson, W. N. Benson, A. B. Walkom, L. A. Cotton, and Miss F. Cohen, and with palzeontological papers by F. Chapman and C. Hedley, will be pub- lished within a few months of the date of issue of the present volume. The latter will contain the index and bibliography. We are fully sensible of the fact that in the present memoir we have probably fallen into many errors, arising possibly from too hasty generalisation from slender data, too imperfect a review of the many valuable memoirs of previous writers on this region (a shortcoming, however, which has been almost unavoidable in view of the fact that the whole of this memoir has been elaborated in Australia, where we have not had access to many memoirs on the “ “The Paleographic Relations of Antarctica,” Chas. Hedley, Proc. Linn. Soc., June 6, 1912. PREFACE xiii Antarctic to be obtained only at European libraries). We are also aware of defects arising from the spasmodic working up of our material. The latter drawback has arisen from the fact that it was necessary to break off from time to time from our study in order to raise funds to defray all the cost, other than that of printing, of the preparation of the memoir. By means of lectures a sum of over £800 has been raised in various parts of Australia and Tasmania, and we are very grateful to the audiences who so generously patronised these lectures, and so made the preparation of the two volumes of this memoir possible. We must add that the Royal Society have generously contributed £200 towards defraying the cost of the publication, the remainder of the cost being borne by Sir Ernest Shackleton. In reference to the photographs reproduced herein, whenever possible we have added the name of the photographer. All were taken by members of the expedition, but in many cases it has now been found impossible to trace the name of the photographer. The rough sketches of the coast-line from Cape Bernacchi to Mount Nansen, and inland towards the South Magnetic Pole, were made by one of us (T. W. E. David), and we are much indebted to Mr. K. Craigie for redrawing these for reproduction. He has also redrawn in black and white several of our photographs, which otherwise would have been too inferior for printing. Our acknowledgments are also due to Mr. H. E. C. Robinson for the great care with which he has prepared our maps and sections. We are indebted above all to Sir Ernest Shackleton for the constant sympathetic encouragement which he gave us throughout in our work, and the invaluable collection of fossils brought back from the Beardmore Glacier by himself, Wild, Adams, and Marshall, under conditions of extreme risk and hardship. We have also to thank our colleague James Murray for useful notes about thaw and ocean currents in the neighbourhood of Cape Royds. Valuable assistance was also rendered us by our late colleague Mr. Bertram Armytage, as well as by other members of the expedition. We are particularly indebted to Mr. C. Hedley, of the Australian Museum, for his contributions on the mollusea of the raised beaches and upthrust marine muds; to Mr. Frederick Chapman, of the National Museum, Melbourne, for his account ot the Foraminifera and Ostracoda derived from these marine muds; as well as to Mr. T. Griffith Taylor for his notes on the Archwocyathine in the Cambrian limestones of the Beardmore Glacier. Professor Skeats, of the University of Melbourne, has contributed important notes on the Cambrian lime- stones, a subject on which, of course, few can speak with such authority. What, perhaps, has been a no less laborious, and in some cases certainly a still more tedious and difficult, task has been the elaboration of our large petrological collection. This work has been done by Dr. Jensen, Professor Woolnough, Dr. Allan Thomson, W. N. Benson, A. B. Walkom, and Dr. D. Mawson, to all of whom we beg to express our hearty gratitude, while to Mawson we owe the map of the coast from Cape Bernacchi to Mount Nansen, compiled from his theodolite survey. Mr. Arthur W. Allen has been unremitting in his kind attention to the business side of our work ; Xiv PREFACE Mr. J. A. Tunnicliffe, of the University of Sydney Library, has much assisted us in the matter of arranging and indexing these notes, as well as in the matter of refer- ences; and certainly not the least important help that we have received has been given by our colleague, Mr. W. 8. Dun, who has been an unfailing source of informa- tion in all matters relating to Antarctic Bibliography. Our hearty thanks are due, and are hereby sincerely tendered, to Dr. Chareot, Professor Penck, Dr. J. Gunnar Andersson, Dr. A. Strahan, G. W. Lamplugh, and Professor Sibly for much sympathetic help. CHAPTER I II. XVI. XVII. XVIII. XIX. CONTENTS PHYSIOGRAPHIC INTRODUCTION DYNAMIC GEOLOGY: PART I. METEOROLOGY, WITH SPECIAL REFERENCE TO TEMPERATURE, SNOWFALL, AND ABLATION DYNAMIC GEOLOGY: PART II. GLACIOLOGY GLACIOLOGY (continued)—CAPE IRIZAR TO DRY VALLEY GLACIOLOGY (continued) —THE FERRAR GLACIER AND ROSS ISLAND GLACIOLOGY (continwed)—THE ROSS BARRIER LAKES AND LAKE ICE OF CAPE ROYDS AND CAPE BARNE ICEBERGS ICE-FOOT AND SEA ICE WEATHERING—DENUDATION—EROSION VULCANISM ORGANIC LIFE STRATIGRAPHICAL GEOLOGY : PRE-CAMBRIAN, CAMBRIAN, AND DEVONIAN DEPOSITS ERUPTIVE ROCKS (PROBABLY POST-CAMBRIAN AND PRE-GOND- WANA) AND THE BEACON SANDSTONE FORMATION CAINOZOIC LAVAS AND TUFFS OF EREBUS OLDER MORAINES AND ERRATICS UPTHRUST MARINE MUDS AND RAISED BEACHES RECENT DEPOSITS, MIRABILITE AND ALGOUS PEAT CAINOZOIC PALHOGEOGRAPHY : PART I. ANCIENT EXTENSION OF THE GLACIERS PART IJ. PROBABLE PRE-GLACIAL HISTORY OF SOUTH VICTORIA LAND IN CAINOZOIC 'TIMES NOTES OF THE GENERAL GEOLOGICAL RELATIONS OF ANT- ARCTICA TO OTHER PARTS OF THE WORLD XV PAGE PLATE XIU. XIV. XV. XVI. XVII. XVIII. LIST OF [LLUSTRATIONS PLATES PAGE Mount Erebus and the foothills in the neighbourhood of the Winter Quarters Frontispiece Fig. 1. Cape Washington seen from the south Facing 4 » 2. Cape Washington os 4 General map showing the chief physiographic and tectonic features of South Victoria Land ss 6 The Antarctic Horst seen from Cape Royds 8 Longitudinal section along Antarctic Horst showing glaciers and faults _ ,, 9 Map showing direction of prevalent winds in South Victoria Land xs 20 Fig. 1. Frost smoke rising from the sea 3 42 > 2. Ice-flowers on sea ice 35 42 Section across Sunk Lake surface near Cape Barne 42 Map of Nansen-Drygalski area of South Victoria Land 5 46 Sketch of coast from Cape Irizar » 48 Sketch of Drygalski Ice Tongue * 52 Fig. 1. Relief Inlet 55 54 » 2. Relief Inlet 3 54 » 3. Pool of sea-water PA 54 » 4. Englacial moraine = 54 » 5. Looking towards the Reeves Glacier 3 54 » 1. Backstairs Passage ss 58 »» 2. Looking down Backstairs Glacier 7 58 » 93. Magnetic Pole Plateau _ 58 » 4. Magnetic Pole Plateau eS 58 Sections along the Drygalski ‘Tongue : 62 Fig. 1. Coast near the Penck Glacier 55 78 » 2 The Nordenskjéld ice-cliff = 78 Granite Harbour and the Mackay Glacier 82 Fig. 1. Entrance to Ferrar Glacier 3 88 » 2. Effect of thaw on Ferrar Glacier ss 88 » 1. River of thaw water at Solitary Rocks 5 90 » 2. Hanging Glacier ” 90 xvil ce XXII. XXIII. XXIV. XXVII. XXVIII. XXIX. XXX. XXXI. XXXII. XXXIII. XXXIV. XXXYV. XXXVI. XX XVII. X XXVIII. XXXIX, LIST OF ILLUSTRATIONS Cliff Glacier near the Ferrar Glacier 2. ‘Vhaw stream on the Ferrar Three thousand feet up the Ferrar Glacier 2. Dry Valley The Butter Point Piedmont Glacier Tongue, Ross Island to} > il. 2. West side of Glacier Tongue 1 . Turk’s Head Glacier 2. Small Glacier Cape Barne Glacier Ice-cliff at the west end of Barne Glacier 1 Q 1. Granite Erratic 2. Erratic of red granite near Backdoor Bay, Cape Royds Ice crystals 2. View across Horseshoe Bay 1. Glacier and terrace near Cape Bird 2. General view of the coast near Cape Bird Pacing Junction of Ross Barrier with the coast of the mainland near Mount Hope ,, View from the top of Mount Hope up the Beardmore Glacier Fig. 1. Lateral moraine on the Beardmore Glacier ” 2. The Cloudmaker Panorama, Beardmore Glacier Beacon Sandstone Coal Measures Three thousand feet up the Beardmore Glacier Plan illustrating direction and rate of movement of the Ross Barrier Fig. 1. Western inlet in the Ross Barrier ” 2. Small inlet in the Ross Barrier The Dreadnought Fi o 1g. ” 1. Edge of Ross Barrier 2. Cliff of Ross Barrier 1. Sounding round a stranded berg 2. The Nimrod moored to the stranded berg Scott’s Depot “ A” The thaw at Green Lake, Cape Royds, during the summer of 1908—09 Fig. 1. Bird’s-eye view of Cape Barne and Cape Royds ” 2. Foothills of Erebus above Cape Royds PLATE XLII. XLII. XLIV. XLV. XLVI. XLVII. XLVIII. XLIX. LII. LI. LIV. LV. Fig. 2 2. LIST OF ILLUSTRATIONS Shaft cut in Green Lake View of Clear Lake near Cape Royds Macrocrystalline ice on Clear Lake Blue Lake Eskers of Blue Lake, Cape Royds Coast Lake, looking towards the south-east Pony Lake, Cape Royds Snow Tabloid, Terrace Lake Deep Lake, Cape Barne Deep Lake, Cape Barne Small berg with projecting foot Barrier berg Tilted iceberg Tilted iceberg Weathered icebergs Fig. 1 2. 3. 4 29 — Sea ice breaking out in late summer of 1907—08 Break-up of the sea ice in McMurdo Sound Heavy pack in the Ross Sea Stream ice along the coast of Ross Island Spray ice on provision cases near Flagstaff Point Sea ice in McMurdo Sound Icefoot at Blacksand Beach Kenyte lava from Mount Erebus, sea ice with ice flowers Ice stalactites formed like horses’ feet Icefoot with sea ice breaking up A snow cornice Stratified ice-cliff at Blacksand Beach The icefoot in late summer Foot stalactites on the icefoot at Cape Royds Loose, small pack in the Ross Sea Heavily snow-covered pack in the Ross Sea Club-shaped icicles at Blacksand Beach Pancake ice. The Nimrod’s wake through pancake ice Heavy pressure ice in McMurdo Sound Loose pancake ice in the Ross Sea Sea ice in Backdoor Bay breaking up New ice forming over a crack Overthrusting along a crack Sea ice with horizontal lamination Facing XX LIST OF ILLUSTRATIONS PLATE PAGE LVI. Fig 1. Frozen sea-spray encrusting boxes of stores Facing 192 » 2. Digging out stores after the cases had been buried in ice during a blizzard 5 192 , 3. View of High Hill, Cape Royds, with Cape Barne on the left in the distance 55 192 » 4. Kenyte lava showing spheroidal weathering - 192 LVII. 55 1. Weathered boulder of kenyte from moraine at Cape Royds 2 194 55 2. Weathered boulder of kenyte on the foothills of Mount Erebus _,, 194 ,, 8. Weathered concretions out of the Beacon Sandstone, Knob Head Mountain 5 194 LVIII. A typical glacier-sculptured valley 5 200 LIX. Fig. 1. Looking south-south-west from Cape Royds across the now nearly snow-free kenyte » «2.02 » 2. Surface of the Ferrar Glacier Fs 202 » 3. Flagstaff Point 02 5 4. Coast at Cape Barne D 202 LX. General Map of South Victoria Land showing chief tectonic features, geological faults, foliation, and volcanic craters » 208 LXI. Fig. 1. Panoramic view of Mount Erebus % 212 »» 2. Telephoto view of Mount Erebus 5 wile LXII. ,,_ 1. Eruption of Mount Erebus on March 10, 1908 UI » 2. View of Erebus looking about east-south-east a 22 » 93. Looking north by west from the summit of Erebus es EQ LXIII. 5, 1. Ice mound round fumarole on floor of second crater of Erebus ,, 214 » 2. Snow fosse at north-west side of rim of second crater ele! LXIV. ,, 1. Pumice from summit of active crater of Erebus 3) BLA ,» 2. The active crater of Erebus 3 214 LXV. Felspar crystals from summit of Mount Erebus Fr 214 LXVI._ Sections through Mount Erebus and through Ross Island 6 LXVII. Fig. 1. Eruption of Erebus oe ~ilG » 2. Eruption of Erebus, June 14, 1908 Rs 216 LXVIII. Final phase of the eruption of Mount Erebus on June 14, 1908 3 218 LXIX. Fig. 1. Parasitic voleanic cone at Cape Bird is 218 5 2. Cape Bird, Ross Island 1S LXX. cS Cape Barne “5 220 20 Basic dyke intersecting agglomerates at Cape Barne Pillar 5 ~ 220 LXXI. ». 1. Parasitic Tuff Cone, chiefly formed of kenyte tuff, near Cape Barne a 222 Mount Cis, a parasitic cone on the slopes of Erebus -, 229 LXXII.,,_ 1. Imaccessible Island on left, part of Tent Island on right, looking north 3 224 Tent Island on left, Inaccessible Island on right, looking north- north-west 3; 224 20 PLATE LX XIII. LXXIV. LXXYV. LXXVI. LX XVII. LXXVIII. LXXIX. LXXX. LXXXI. LXXXII. LX XXIII. LXXXIV. LXXXV. LXXXVI. LIST OF ILLUSTRATIONS Xxi AGE Fig. 1. Inaccessible Island showing the glaciated summit Facing 226 »» 2. North-east end of Inaccessible Island showing frost-splintered cliff of basic lava ae 226 »» 1. Tent Island, showing coarse volcanic agglomerate ec 228 » 2. Beaufort Island &: 228 Sections through the Antarctic Horst % 232 Fig. 1. Microscopic photographs of Archeocyathine eo) bb) 2. ”° ” bb) 35 940 » 3. 23 3 03 » 240 29 4. ” ” ” ” 240 3° 5. 3 ” ” 3% 240 ” 6. ” ” ” 9 240 >} Me ” bb) 3” bb) 240 » 2. 9 D » 240 ” 3. ” bb) 3 35 240 » 4. ” * ” 9 240 bb) 5. bb] ”° >) ” 240 3” 6. 3” ” 99 ” 240 ”° 1. 93 bb) ” oy) 240 bb) 2. ” bb) bb) bbl 240 3” 3. ” ” bb) ” 240 ” 4, 3” 3” ” bb) 240 ” 5. 3” 3° ” bb} 240 » 6. » >» %» » 240 ” Ve 3” ”° 3” 240 » 2 An organism of unknown affinities a 240 » 3. Section of trilobite ? 5 240 55 4. Fragment of thickened body wall of Archxo. yathus Fe 240 » 5. Tuning-fork spicule allied to Lelapia 240 » 6. Spicule from a Lyssacine sponge » 240 Glaciated boulder of Cambrian (?) oolitic limestone 242 Inclusions of sphene diorite in foliated granite, Depot Island = 246 Fig. 1. The western party camped on the Ferrar Glacier = Q54 5 2. Sill of quartz-dolerite with granite above it BS Q54 5 1. Typical weathered surface of kenyte lava = 256 » 2. View showing jointing in kenyte lava ie 256 General view looking from Cape Royds towards Cape Barne “5 262 Fig. 1. Moraine mounds, possibly eskers, Blue Lake a 262 »» 2. Moraines left by the old Ross Barrier 5 eae » 1. Typical striated boulder of fine-grained quartzite 262 s 2. Small striated boulders from old moraines of the Ross region of Antarctica 33 262 xxii LIST OF ILLUSTRATIONS PLATE PAGE LXXXVII._ Fig. 1. Moraine cone with raised beach material Facing 266 » 2. Upthrust serpulz deposits 3 266 LXXA VIII. » |. Lyothyrina Antarctica (Blockmann) Me 272 »» 2. Siliceous sponge spicules ps Q72 », 93. Tubes of Serpula, Polyzoa, and valve of Chiton 35 272 5, 4. Undescribed simple coral 5 272 33 5. ° . 39 272 1EPOOSIDK, » 1. Pecten Colbecki, seals teeth, appendage of crustacean; from raised beach of Dry Valley y 272 » 2. ot TONGUE H eeeeecce Probable Faults. : volcanic. Foc Probable Volcanic Fact ¥ Dykes "San Giacitky r: ries Foliation of gneiss & gneissic granite 1 NORDENSKIOLD ICE BARRIER | TONGUE | Parting of the Wire's on Magnetic Pole Flateau. M=Davidso L Mrveviggon | NOTE. | | Altitudes South of Lat 76°S and Map\South of Lat 77°S any West OF Cape Washington are mostly taken from the data af i Expedition, - hs Akes to Mi Murdo Sound after 0 Mamsc Me Morrison —= Fest of Map after Cop" RF Scott MOUNT | C Armitage | f Ace | GENERAL MAP SHOWING THE CHIEF PHYSIOGRAPHIC AND TECTONIC FEATURES OF SOUTH VICTORIA LAND 8 VALLEYS OF THE HORST schists, gneiss, granite, slate, and altered limestone. A plateau of crystalline rock, extending eastwards from the eastern base of Mount Lister for a distance of about 10 to 12 miles (18-19 kilometres) in width, appears to bea very ancient peneplain. This may be a Pre-‘‘ Beacon Sandstone” peneplain, that is probably a Pre-Gondwana peneplain.* This has been ‘‘ re-discovered” by erosion in Cainozoic time. Its height above sea level varies from about 4000 feet to 6000 feet. The figure below is a general panoramic view from our winter quarters at Cape Royds on Ross Island, looking westwards over 50 miles (80 kilometres) across McMurdo Sound to the Western Mountains. Valleys. ‘The Section, Plate V., shows the position and relative sizes of these transverse valleys, mostly of the “outlet” or Greenlandic type, which transect the Antarctic Horst. The valleys may be divided, broadly, into (1) outlet valleys, where they cross the horst and form spillways for the inland ice reservoirs, and (2) alpine valleys, where they do not completely transect the horst, and thus merely discharge glacier ice formed within the drainage-area of the horst itself. These Alpine valleys have their “thalweg” mostly athwart the long axis of the horst, but some are parallel to this axis, ike South Arm on the Ferrar Glacier, and the Mill, Keltie, and Hood Glaciers of the Beardmore Glacier. These longitudinal (subsequent) Alpine valleys may be in the first case of tectonic origin following fault planes parallel to the main lines of faulting which bound the Antarctic Horst. Both types of valleys, outlet as well as Alpine, have numerous hanging valleys emptying into them. The main valleys, especially the outlet valleys, offer such impressive examples of ice-erosion as should convince even the most sceptical that glacier ice is able to carve rock on a grand scale. They are mostly very steep-walled and either spurless or with intensely faceted spurs. Details of these are given later in this report under the head of Glaciology, where the question is discussed as to how far the valleys are tectonic and how far glacial or fluviatile in origin. The interesting problem is also investigated as to how far the glacial ice streams have brought their channels to grade, the conclusion being that the channels are not by any means brought to grade on the inland side of the great horst. If Antarctica were bared of its snow and ice, extensive lakes would probably gather immediately to the west of the horst. Plains. The steep coast of South Victoria Land is subtended for about 200 miles (319 kilometres) northwards from the head of McMurdo Sound by a remarkable plain. This is from 10 to 15 miles (16-24 kilometres) in width, and slopes up at a gentle angle to a height of from about 1000 feet to 1700 feet (805-518 metres) to * In view of the resemblance of the lower portions of the Beacon Sandstone to the Devonian rocks of the Falkland Islands, as explained in the last chapter of this volume, and especially in view of the recent discovery by T. Griffith Taylor and F. Debenham, of the late Captain Scott’s expedition, of bony plates, aseribed by Dr, A. S. Woodward to Devonian fish, this peneplain, in part at any rate, may be Pre-Devonian. PLATE IV THE ANTARCTIC HORST SEEN FROM CAPE ROYDS | Zo face Pp. 5 PLATE V VOLCANIC ZONE OF VOLCANIC ZONE OF NORTH M” DISCOVERY EREBUS & TERROR + Lister vauuey json MtChet mynd MiNansen so maceintock we ony Late mn’ Bapue (so se00 renana' wmengund yor smugre BARNE , Pemex GUC Mra : re GLACIER 1 " , ‘ : 1 aur? Fault ras? PAUL rar rau raur LONGITUDINAL SECTION ALONG ANTARCTIC HORST SHOWING GLACIERS AND FAULTS [To face p. 9 PLATE V NORTH acier — MGerlache MENansen SKI ‘ 000 IRRIER . +t ‘ | MfLarsen : meMglbourne ‘sell + 5000 | BSene | Bellingshausen ; HansenNunatak } : M®Baxter [To face p. 9 COASTAL PLAIN 9 the steep foothills of the plateau. As it is for the most part covered by the ice of the piedmont aground, one can do little more than guess at its structure. A study of its surface, where it outcrops from beneath the ice in the coastal clifts, shows that for a considerable extent it is formed of an intensely glaciated surface of ancient erystalline rocks with the hollows filled with a thin covering of moraine material. The deepest hollows, being below the sea level, could not be examined. No true boulder clay (till) was observed. It has been suggested that this coastal plain represents a down-faulted segment, but, at present, evidence of such faulting is wanting. Mr. E. C. Andrews, of the Geological Survey of New South Wales, suggests that it is an old plain of marine erosion, and it may be so. It is also possible that it may represent an abrasion shelf notched back by the Ross Barrier at the time of maximum glaciation. To this last suggestion it may be objected that, during the maximum glaciation, the pressure of the local glaciers of the Western Mountains would suffice to repel, or shoulder away, encroachments on the coast by the Ross Barrier. The Barrier may, however, have shouldered them around northwards and commandeered them, so to speak, for the work of eroding the terrace. It seems a gigantic work for ice to have accomplished, but a mass of moving ice (and we know from the evidence of the erratics that it was certainly moving) 500 miles (805 kilometres) wide, and some 3000 to-4000 feet thick (914-1219 metres), represents a vast erosive force. It might also be suggested that this coastal plain represents in part an old plain of aggradation, that is formed from deposition of continental waste, resting on an ancient plain of marine erosion, somewhat analogous to the coastal platform of the Malaspina Glacier.* As far as our observations extend, there is no great thickness of alluvial material resting on the glaciated surface of crystalline rock. Unfortunately we have only a few soundings, too few to admit of the construction of a continuous curve from where this plain ends at the coast down to the greater depths of Ross Sea. The few soundings that were taken imdicate depths of from 350 to 450 fathoms within 12 miles of the coast, deepening to over 650 fathoms in the neighbourhood of a large glacier, like that which forms the Drygalski Ice Barrier Tongue. The following is a section across this coastal platform from Mount Davidson to Mount Erebus : It will be noticed that after the soundings, taken from W. to E., deepen to 350 fathoms at 12 miles E. of the coast platform, they shoal to 110 fathoms in the middle of McMurdo Sound, then deepen again to 460 fathoms at only three miles off the west coast of Ross Island. This shallowing towards the centre of the Sound is probably due to the vast amount of morainic material carried northward by the former Great Ice Barrier, when at its maximum, from the neighbourhood of Mount Discovery, or possibly it may be due to a submerged chain of small volcanoes. Probably the former is the correct explanation. * TI. C. Russell, 1899; R. 8, Tarr, 1907; L. Martin, 1909. 10 THE ROSS SEA AND McMURDO SOUND VICTORIA showing line of Section GEOGRAPHICAL MILES ° 10 E165 HORIZONTAL SCALE OF GEOGRAPHICAL MILES. 5 C) 10 20 so —*—_—~*KX_—$—_—————————————————> VERTICAL SCALP OF FEET. 10,000 5000 ° 10,000, ee Coastal Pratform. | Present Glacier. pot id: | Long.166"E. tong 164°E tong. (63°E, Fies. 1 anp 2. SECTION ACROSS McMURDO SOUND Looking south, showing coastal platform on right, and rapid descent of sea floor to depth of 360 fathoms. A third possible explanation of the shallowing of McMurdo Sound towards the centre is that it is the result not of addition of morainic or voleanic material, but of differential erosion. In this case it may be suggested that deeper hollows have been scooped inshore, where the thrust and consequent erosive power of the former THE ROSS SEA AND McMURDO SOUND 11 great glaciers of the Western Mountains of South Victoria Land and of Erebus were perhaps greater than that of the central part of the great glacier which once moved down McMurdo Sound. Ross Sea and McMurdo Sound. The boundaries of Ross Sea have already been given. Apart from the large number of valuable soundings recently taken by the British Antarctic Expedition of 1910-13 on the Terra Nova, and those of the Discovery Expedition of 1901-4, soundings hitherto have been few and far between. Captain F. P. Evans, R.N.R., and Lieutenant J. K. Davis of our Expedition took soundings wherever practicable, but the opportunities were few, about twenty only being recorded. Some of our soundings across McMurdo Sound have already been given, and these added to the important series taken by Captain R. F. Scott, on the Discovery, from Ross Island to King Edward VII. Land give some indication of the shape of this part of the Ross Sea basin. The Ross Sea is about 650 miles in width from west to east at its entrance, but the eastern side is so beset with pack ice that the actual land boundary there is not known. In the latitude of Ross Island the width of Ross Sea including that of McMurdo Sound is at least 550 miles. Practically the whole of the Ross Barrier is but a southerly prolongation of Ross Sea. Ross Sea from its southernmost point, at the junction with it of the Devil’s Glacier, northwards to where it meets the Southern Ocean measures about 500 miles. Its depth near the latitude of Ross Island varies from about 200 to 460 fathoms. As one approaches the edge of the Barrier, within 100 miles or so, the water becomes noticeably green in colour, owing probably to the otherwise blue water being stippled with the innumerable yellow flecks furnished by countless hosts of living diatoms. Of special geological interest, from the point of view of glaciology, are the horizontal and vertical distribution of temperature in Ross Sea, and the directions of the prevalent tidal and other currents. Unfortunately as yet details are meagre, ut such as are available are of distinct interest. First in regard to currents, some interesting notes on these have been published by our colleague, James Murray.* The vane of our tide-gauge off Cape Royds was not affected by tidal currents, at all events not appreciably so, as its depth below the surface was 16 feet (4.87 m.). The vane usually pointed nearly due N.W., but oscillated between N. 10° W., and W. 20° N. The fact that all through the winter of 1911 Amundsen observed open water only about 8 miles (13 kil.) N. of Framheim, in the Bay of Whales, in spite of the intense cold of the neighbourhood of Framheim, demands the advection of warm currents from the north. It may be added that it is not only in the case of the S.E. corner of Ross Sea, near the Bay of Whales, that the sea remains open for the whole * “The Heart of the Antarctic,” vol. ii. pp. 372-375. 12 THE ROSS SEA year. Itis doubtful whether even in the coldest month (July), McMurdo Sound was completely frozen over, even when the mean temperature was —17° F. (— 27° C.). Usually there was a long dark streak of open water about 15 to 20 miles off the land, as shown in the drawing by Mr. K. Craigie from an inferior photograph, showing the Western Mountains. To the north of Black Sand Beach, about one mile north of Cape Royds, there was open sea most of the winter. Murray (op. cit. p. 873) quotes good evidence to show that at times there was a southerly current coming down from the direction of Cape Royds as far as Black Sand Beach, about a mile north of Cape Royds. Thence the current turned west- wards across McMurdo Sound, and thence northwards towards Granite Harbour and the Nordenskjéld Ice Barrier Tongue. The large number of stranded bergs along the west coast of Ross Sea renders it probable that the current, on the whole, has a northerly set from McMurdo Sound along its western shores. Strong off-shore winds from the Western Mountains, often immediately preceded by southerly and south-easterly blizzards, would tend to give the water of Ross Sea a clockwise rotation, which would be further accelerated by the easterly winds of King Edward VII. Land. It seems very possible that the water of Ross Sea moves as a gigantic eddy, the southern edge of which passes under the Ross Barrier proper, while its south-western portion passes under the Barrier to the south of Ross Island and flows northerly up MeMurdo Sound.* Temperature. We have no sufticient data on the subject of the horizontal distribution of temperature over Ross Sea, so the following suggestions are very tentative. In reference to the vertical distribution of temperature we may quote the following important observation by Sir J. C. Ross, quoted by Commander Hepworth : f “On January 6, 1841, at noon, they (the Hrebus and Terror) were in latitude 68° 17’ S., longitude 175° 21’ E., and found that they had been set twenty-six miles to the S.E. by the current during the previous two days. Here the temperature of the water at 600 fathoms was found to be 39°8° F.; at 450 fathoms, 39°2°; at 300 fathoms, 38°2°; at 150 fathoms, 37°5°; and at the surface 28° F.” Ross’s thermometers were not protected against pressure by being sealed up in a strong outer glass tube as are modern thermometers. Nevertheless, this inversion of temperature with depth cannot all be ascribed to increase of pressure on the bulb of the thermometer. It may be mentioned that at a depth of over 620 fathoms, at the Drygalski Glacier, J. K. Davis on the Nemrod registered a temperature of about 40° F. This was so high that we discredited it at the time (February 5-6, 1909), * Dr, W.S. Bruce and R. C. Mossman of the Scottish National Antarctic Expedition, 1902-4, hold that a similar eddy exists in Weddell Sea. Lieutenant Filchner in the Deutschland experienced a similar current circulation, as proved by the direction of drift of his ship. t+ “National Antarctic Expedition,” 1901-4. ‘ Meteorology,” part i, p. 420, TEMPERATURE OF THE ROSS SEA 13 but while we do not claim that these temperatures are absolutely accurate. we are of opinion that the following considerations suggest that there is a slight inversion of temperature in much of the water of Ross Sea. Firstly, there can be no doubt that the sea ice of a preceding winter season is melted from below as summer approaches, so that 7 feet (2°13 metres) of sea ice towards the end of the summer may be less than 5 feet (1°5 metres) in thickness, In other words, half a metre may be lost annually to the sea ice near the latitude of Mount Erebus as the result of melting from below.* Secondly it was noticed that there was a tendency for open pools of water to form and keep open even during the winter at any point in Ross Sea where there was any obstacle, such as a submerged ridge or moraine which tended to deflect currents upwards. The pool of sea water which remained unfrozen until late in May to the north of the Cape Barne Glacier, the pool off the submerged moraine to west of Cape Armytage, and possibly the large strip of open water on the north side of the Drygalski Glacier, may be due to the upward deflection of warmer but more saline water, so that locally it rises above the surface colder but fresher water. This explanation of these pools seems more reasonable than the hypothesis that they may be due to the local warming effect of hot springs situated along lines of faulting. Ina region of such modern volcanic activity such springs are almost sure to exist, but their heating effect on the vast body of water in Ross Sea would probably be negligible. * Unfortunately we have only approximate data on this subject. The above statement is based on the fact that whereas we found that the sea ice acquired a thickness at Cape Royds, in 1908, of 7 feet (2:13 m.) during autumn, winter, and spring, in January its thickness had been reduced to about 5 feet (1:5 m.) with numerous intervening corrosion hollows where the thickness was less than 1 foot (‘3 m,). 7 That these open pools are connected with upward deflected currents seems highly probable. What is now needed is a series of accurate vertical temperatures at type localities. These will no doubt in part be supplied by the future reports of the recent British Expedition under Captain R. F. Scott. CHAPTER II DYNAMIC GEOLOGY PART I. METEOROLOGICAL NOTES, WITH SPECIAL REFERENCE TO TEMPERATURE, SNOWFALL, AND ABLATION Temperature. The close coincidence of the Temperature Pole with the Geographic Pole in Antarctica obviously constitutes ideal conditions for an immense permanent anticyclone if the land had been of low altitude, but, as Dr. W. N. Shaw has recently pointed out to us, the problem is much complicated by the rock and ice dome of the Antarctic taking the place of so much of what otherwise would have been the lower part of this anticyclone. The steep grade in temperature between land and water, often as much as 30° or 40° Fahr. within a mile back from the coast, combined with the vast amount of open sea in which the continent is placed, and the comparatively steep downgrade from the centre of the land to the coast, contribute to make the Antarctic the home of winds of a violence and persistence without precedent in any other part of the world. A continent of the shape, relief, and situation of Antarctica must always dominate local weather conditions. For example, it can scarcely be possible for weather conditions on the coast of one side of such a continent to travel across its altitude of upwards of 10,000 feet and descend on the other side. Such a movement would probably be possible only where the continent is very narrow, as at the “stalk of the pear” in the American sector of Antarctica. Since the discovery by Amundsen of the remarkably low temperature area south of the Bay of Whales, on the Ross Barrier, where the mean temperature in August 1911 was —44°5° C. (—48'1° F.), the suggestion by him that there may be at least two temperature poles (Cold-Poles) in Antarctica seems very plausible. In the Northern Hemisphere there are two such poles, one almost identical with the North Pole, the other near Verkhoyansk in Siberia. Amundsen’s Cold-Pole on the Ross Barrier is obviously to be correlated with the calm state of the atmosphere in that region, a fact in turn dependent on the absence of high mountain ranges in the eastern region adjacent to Ross Sea. The Antarctic Horst, 10,000 to 15,000 feet high, is a powerful disturbing factor on the west side of Ross Sea. The high winds generated largely by it lead to a rapid interchange of air between the South Pole and warmer latitudes, and so tend to raise temperatures. 14 COMPARATIVE TEMPERATURES 15 The table of temperatures given below is for our winter quarters at Cape Royds, for the Discovery winter quarters at Hut Point, and Borchgrevink’s winter quarters at Cape Adare. Cape Royds was badly situated for obtaining accurate records of Antarctic temperatures on account of its close proximity to open water. For some reason which we were unable to determine there was a strip of open water in the middle of McMurdo Sound late into the winter, and it persisted through September and October into the summer. At times, especially after blizzards, this open water would extend close up to Cape Royds, and would, of course, raise the temperatures at those seasons of the year, as the surface temperature of the water was, of course, not below 28° Fahr., and therefore far above that of the adjacent coast, which was below zero from April to September inclusive. The same cause no doubt contributed to make the snowfall at Cape Royds abnormally high for that latitude. 30 mc. = ceT] 2 | i= = y | Zia wo o o- f ces) = f=>) a o- Fie. 3. TEMPERATURE CURVES These curves have been constructed from the figures given by Dr. H. R. Mill in his article on the Polar Regions in the “ Encyclopedia Britannica,” vol. 21. These Tables, shown as curves, suggest the following interesting results : Hut Point, although only about 24 miles southerly from Cape Royds, is much colder than the latter in early winter, when the former is some 25 miles distant from open water, whereas the latter is seldom more than about 10 miles from it, and frequently after blizzards within a mile of it. In August it will be seen that the curves for Hut Point and Cape Royds nearly touch one another. By this time, and for some little time previous, the whole of McMurdo Sound, with the exception perhaps of a very narrow strip near the centre, appeared to be frozen over. In September the ice began to break away from McMurdo Sound, exposing a relatively warm sea surface to within a mile of our winter quarters ; and it will be noticed that the temperatures at Cape Royds at once rose considerably above those of Hut Point. By November and early December, at which time a large proportion of McMurdo Sound is ice-free, the temperatures again approached one another nearly. The fact must be borne in mind that these figures are for different years, the Discovery for 16 METEOROLOGY 1903, and the Cape Royds for 1908 ; but the figures for the Doscovery observations at Hut Point for 1902 show similar features. The lowest temperature we recorded was — 59° F. on the Great Ice Barrier late in September 1908. On August 15 of the same year on the Barrier, at a point about 10 miles 8S. of Cape Armytage, the thermometer registered — 57° F. Vertical Distribution of Atmospheric Temperature. Of great interest geologically and meteorologically from the point of view of the origin of snow in the Antarctic, is the distribution of temperature vertically and horizontally. This matter is discussed in some detail in the meteorological report of the Expedition, so a brief summary will suffice here. As regards vertical distribution, we obtained three pieces of evidence. Tempera- tures taken (1) on the ascent of Mount Erebus, (2) on the journey furthest south, (3) on the journey to the Magnetic Pole area. All three journeys, especially the two Degrees Fahrenheit. i) 1000 ©2000 ©« 3000 ©4000 «5000 +6000 +7000 © «8000 :-« 3000 :-=«000-«w00D-«reooO ©3000 14000 Feet. Feet. Fia. 4. TEMPERATURE CURVE ON ASCENT OF MOUNT EREBUS March 5 to March 10, 1908. last, give some information as to the horizontal distribution of temperature. For vertical distribution the Erebus observations are obviously the most important, for Erebus, rising steeply as a huge isolated cone to over 13,000 feet above sea level, probably does not seriously disturb the circulation of the upper atmosphere by the upward deflection that is occasioned by the edge of a high continent or the mass of a large mountain range. The curve shown in the figure is, as stated, only a rough approximation. There may be an error in places of as much as 3° or 4° F., but the main fact is brought out conspicuously that there is a very steep gradient of temperature showing a fall of about 1° F. per 150 feet, from sea level up to about 3500 feet, and from that altitude up to 13,300 feet the fall is only about 1° F. per 1000 feet. The extra steep fall from 3500 feet to sea level is no doubt due in part to the proximity of the relatively warm water of McMurdo Sound, for the Sound was only just beginning to freeze over when we ascended Erebus; partly it may be due to the settling down of the cold air from the upper part of the great cone of Erebus to its VERTICAL DISTRIBUTION OF TEMPERATURE 17 base at about 7000 feet above sea level, and spreading thence downwards over the snow-covered lava sheets to a level of about 3500 feet. Such tendencies to inversion of temperature as one ascends mountains are of course common at the beginning of and during winter, serving to emphasize the fact that during winter the earth's atmosphere cools from the base upwards, and not from above downwards. These conditions obviously tended to unduly raise the snowfall near Cape Royds, where the warm air from off the sea met the cold air descending from Erebus. The average fall of atmospheric temperature from sea level to the top of Erebus is about 1° F. per 400 feet, which is not very different from the gradient in temperate latitudes, though of course the grade is less steep. It is suggested that the lessening in the rate of fall of temperature may have been due in part to the strong N.W. air current which swings, during a blizzard, into a N. and 8. direction. This must have been blowing for some time over the top of Erebus during the furious blizzard of March 8, the day before we reached the crater. Such a high-level wind blowing from northern latitudes would of course be warmer than the normal W.S.W. wind which sweeps from off the continental plateau over Erebus. As regards the evidence of vertical distribution of temperature obtained on the journey of the Northern party to the Magnetic Pole area data are wanting for accurate comparison, on account of our distance from the base at Cape Royds, where the check temperatures were taken (about 400 miles at the maximum limit). Thus we can form only a rough idea from the temperatures at our base at Cape Royds what the temperatures at sea level on our route were likely to have been.* In considering the distribution of temperature on the Magnetic Pole Plateau one must remember, that in advancing from the coast inland one has first to cross the block mountains of the coastal horst, and in these mountains, in summer time, a considerable amount of dark rock is exposed to the sun and absorbs its heat rays. At the back of this horst the plateau rises in a distance of about 180 miles to about 7350 feet above sea level. On account of the difference in specific heat between land and water, together with the absence of convection currents in the rock material of the land,+ there is a considerable difference, in summer time, between the tempera- ture of the sea water, and that of the rocks of the adjacent horst. Hence the air over the horst, by day especially, becomes warmer than the air over Ross Sea. The difference in specific heat between ice and water would have the same effect. * The temperature obtained by Bernacchi for Cape Adare, at sea level, at 330 miles N.N.E. of Mount Nansen, are for another year (1903-4), but give one some idea as to what increase of temperature to adopt on our base temperatures at Cape Royds. We also have our own observations on the sea ice for over 200 miles N. of Cape Royds, 1908-9, as a check, as well as the temperatures taken by the Vimrod on her second outward voyage through Ross Sea. During part of this time she was locked in the ice-pack at the time that we were ascending the Magnetic Pole Plateau. + The specific heat of water at 15° C. being taken as 1:000, the specific heat of granite, of which most of the exposed rocks of the plateau are composed, may be taken as “192 at12-100°C. (“Smithsonian Physical Tables,” pp. 229-251.) ra 18 METEOROLOGY The specific heat of sea water having a sp. gr. of 10043 at 175° C. being taken as ‘980, that of ice may be taken as follows : =18° to =—7s°C. ~ A468 SP # — 188°C. 285 == 188° i — 252°C. 146% This appears to be an extremely important point in connexion with the wind circula- tion on the Magnetic Pole Plateau, and one which has not yet been properly emphasized in glaciological works. In other words, ice would heat up under the sun’s rays, at the prevalent Antarctic temperatures, at about twice the rate of sea water, and in the greater cold of winter, so long as it was exposed to the sun, at a considerably increased rate. This would, of course, tend to raise air temperatures by day over the plateau, and so check the plateau wind which springs up so regularly during the night. As soon as the increasing heat of the sun towards noon had sufficiently warmed the snow to make the temperature of the air in contact with it approximate to that of the air over the water of Ross Sea, the plateau wind ceased. At night the snow of the plateau parted readily with its heat, and the air above it became chilled and heavy, and commenced to flow seawards as the plateau wind. Hence the much greater daily range of temperature on the plateau than alongside of the open waters of Ross Sea. At Cape Royds in December the daily range in temperature was about 5° Fahr. At the Drygalski Ice Barrier close to the open water at Relief Inlet the temperature was even more constant between night and day when neither the plateau wind nor the blizzard winds were blowing. On the plateau, the daily range of tem- perature during the end of December and January was of the order of about 20° Fahr. ft The specific heat of basalt at 12° — 100° C. is ‘1996, as compared with that of ice at — 18° to —78° C. of 463. It is possible that, to a less extent of course, a similar phenomenon takes place with snow crystals on the plateau. Ice does not readily thaw in the sun’s rays when the temperature of the air is below freezing-point on account of the relatively rapid conduction of ice, cold from the lower layers of ice being quickly transferred to its upper surface when slow convection currents are set * “Smithsonian Physical Tables,” p. 230. + We had no minimum thermometer with us on our journey over the Magnetic Plateau, The small spirit minimum thermometer did not work satisfactorily. Hence there are no records of the temperatures between 11 P.w and about 5 A.m., so the above figure is only approximate. At the same time the figures are the average of a considerable number of daily readings with a sling thermometer, and so are fairly reliable. This comparatively low specific heat of ice also suggests a reason for the rapid sublimation of the snow, and possibly for even a slight thawing below its surface, in the direct rays of the sun on the plateau, at a time when the general air temperature was far below thaw point. On the slopes of Erebus at about 9000 feet above sea level, on March 10, 1908, when the shade temperature was about 0° Fahr., the black rocks were quite warm to the touch, and the snow around them was melting rapidly. TEMPERATURE AND PLATEAU SNOW it up by a warming of the ice surface by the sun’s rays. Snow crystals, however, are separated by non-conducting air gaps from the cold snow crystals below, and thus the heat rays of the sun are free to deal with each snow-flake, as a separate unit, and may melt it, and allow it to re-crystallise in the form which Dr. Mawson likened to anthracene. On January 6, 1909, the surface of the snow seemed softened as we sledged over it on the plateau at an altitude of over 7000 feet, when the temperature at its highest was only about 5° Fahr. On January 14, 1909, when the sun’s rays made themselves strongly felt, the snow surface was carpeted with a dazzling sheet, about half an inch in thickness, of these “anthracene” ice crystals. They were each about half an inch in width, and about 4); of an inch in thickness.* In the ablation of the snow surface of the plateau the snow may thus disappear partly as water vapour, partly as ice vapour, if, as seems possible, the snow surface for the depth of half an inch or so can actually thaw while the shade temperature of the air, except where actually in contact with the snow, is below freezing-point. Another interesting result from the difference in specific heat between rock and ice is that blocks of rock in the Antarctic, where the amount of insolation, during the months of the midnight sun, is very great, have a much more marked tendency to countersink themselves into the glacier ice than is the case with morainic blocks on the glaciers of the Swiss Alps. In fact, soon after leaving the last source of rock supply, these Antarctic moraines have so far sunk themselves below the surface of the glacier that they completely disappear, becoming englacial moraine. Very low temperatures were experienced by Shackleion’s party on the King Edward VII. Plateau, during a great blizzard which commenced on January 6, 1909. The wind at first was S.S.W., the temperature at noon being — 25° F. at latitude 88° 7’ S., longitude 162° E., altitude about 9837 feet. The next day the wind was blowing very hard from the 8.S.E., with squalls of terrific force. The temperature at noon was— 33° F. On January 8, the wind hauled to the 8.E., and blew harder than ever, with hurricane force. The noon temperature was— 40° F. This blizzard gradually slackened in the early morning of January 9. It is interesting to note that in the case of this blizzard there was no Fohn effect. In fact the temperature fell a good deal below what appears to have been normal at that time of year for that locality, the normal temperature at noon being assumed to be about — 20° F. ( — 28°8° C.). In regard to rise of temperature with blizzard winds we experienced rises of temperature towards the end of a blizzard of as much as, in extreme cases, 42° to * That snow may melt when the general air temperature is probably considerably below thaw point is suggested by Amundsen’s observation of icicles at Christmas 1911, hanging from his snow beacons at The Butchery “ Dog Depot,” at an altitude of 10,000 feet above the sea and near lat. 86° S. It is highly improbable in view of the temperatures registered there by Amundsen, that there is ever a true thaw due to air temperature rising above freezing-point. An alternative explanation of the anthracene-like ice crystals, so common on the plateau after days of strong sunlight, is that they were formed during the succeeding night as the result of the condensation of ice vapour due to sublimation. 20 METEOROLOGY 45° F. (23°3° C. to 25° C.) the temperature in one case rising, at Cape Royds from — 30° F. to 15° F. (— 34° C. to—8°C.). While there are obvious reasons for believing that some of this rise of temperature is due to Fohn effect, and caused by the compression of air diving from a height on to the South Pole Plateau, and thence diving again on to the Ross Barrier, we consider that the Foéhn effect is not by any means responsible for it all, but that the rise of temperature, as Commander Hepworth has suggested,* is due in a great measure to the rapid transfer of warm air at a high level in the Antarctic cyclone to replace the air that is lost during a blizzard originating near the Temperature Pole. Finally in regard to the temperature of the Antarctic Regions as compared with the Arctic, the following explanations of well-known facts, though obvious, have not, as far as we are aware, found their way into text-books, so that we may venture to quote them here. Antarctica differs from the Arctic chiefly in the lowness of the Antarctic summer temperature, and the lesser cold of Antarctica as compared with the Arctic in their respective winters. According to Hann’s figures the mean winter temperature at the North Pole in January is — 41°8° F., whereas in the corresponding winter month, July, in the Southern Hemisphere the mean temperature is about — 28° F.f This greater winter cold in the Arctic as compared with the Antarctic is surely due chiefly to the geographical differences between the North and South Poles respectively. In winter not only is the whole of the Arctic Ocean frozen over, but the isotherm of freezing is down to a mean position in January of about 48° N. lat. In the month of July in the Southern Hemisphere the mean isotherm of freezing is situated in about 55° S. lat. This gives an area below freezing in the month of January in the Northern Hemisphere half as much again as that at a similar temperature during the winter of the Southern Hemisphere. Thus there is a mass action tending to increase cold in the Northern as compared with the Southern Hemisphere winter. The cold is further increased in the Northern Hemisphere by the surface relief, which is the very opposite in the two hemispheres. In the Southern Hemisphere the normal curve of the earth spheroid is bulged outwards into a huge dome which acts at once as a gigantic starter of convection currents, and so leads to a rapid interchange of air between the Temperature Pole and warmer regions ; on the other hand, the Arctic Ocean is encircled by land much of which being fairly high acts as a wall of circumvallation to retain the cold air at the North Pole during winter, and by keeping it from moving checks convection currents, and stops access of warmer air from the south. On the other hand, in Antarctica, even in the depth of winter, no part of the continent is more than 1000 miles distant from * “National Antarctic Expedition,” 1901-4. ‘“ Meteorology,” part i. p. 449. + We have now the information that Amundsen found the mean temperature, for August 1911, at the edge of the Ross Burrier, in the Bay of Whales, at Framheim no less than -—48-1° F. (-44°5° c) This may modify the above argument in so far as relates to winter temperatures in Antarctica. PLATE VI —— MAP SHOWING DIRECTION OF PREVALENT WINDS in South Victoria Land and on King Edward Vil Plateau as evidenced by the trend of the Sastrugi Scale of Statute Miles. o 100 50 200 9 Scale of Geographical Miles SOUTH POLE © 22 METEOROLOGY the nearest open sea, the temperature of which cannot be below 28° F. The steep isotherm grade in Antarctica, combined with the quaquaversal slope of the land sea- wards from the Southern Temperature Pole all tend to further accelerate convection currents, and so promote advection of relatively warm air in winter, except in flat areas like Framheim and the Ross Barrier to the south, remote from mountains or plateaux. In summer the ice of the Arctic Ocean breaks up, and wide lanes of open water penetrate to the North Pole itself, and this open water breathes warmth into the surrounding air. Moreover the permanent surface cyclone of summer is con- stantly carrying in warmth to the North Pole at that season. On the other hand during the Antarctic summer the high gently domed land-mass, capped by a per- manent anticyclone, blows cold air outwards spiralling seawards, and keeping down the temperature along its coasts to near freezing-point, and according to Meinardus and Hann, making the temperature at the South Pole, reduced to sea level, about 21:2° F. (— 6°5° C.) for the month of January.* Such geographical differences appear to offer a partial, if not a complete, explanation of the existence of such different temperatures on the same parallels or latitude, as have been recorded from the Arctic and the Antarctic respectively. The matter is thus referred to by Dr. H. R. Mill: F “Even in the South Orkneys, in latitude 60°, in the three warmest months, the air scarcely rises above the freezing-point as an average, while in Shetland (60° N.) the temperature of the summer months averages 54° F. But, on the other hand, the warmest month of the year even in 77° S. has had a mean temperature as high as 30°.” Prevalent Winds, The accompanying map (Plate VI.) shows the direction of all hard snow ridges separated from one another by furrows torn the principal sastrugi out of the hard snow by the fury of the blizzards. From the south end of Ross Island as far as 88° S., the information was obtained by Lieutenant Adams; while those from Mount Erebus, to the South Magnetic Pole Area, were obtained by our Northern party. The sastrugi directions on the plateau west of the Royal Society Range are taken from the description in Captain R. F. Scott’s “ Voyage of the Dzscovery.” The importance, in control of surface wind directions, of distribution of land and water, and the relief of the land is at once apparent from this map. The sastrugi from 88° 8. on the King Edward VII. Plateau, northwards as far as 80° 30’, come from between 8. and §.E., modified by the presence of the outlet glaciers, such as Beardmore Glacier, and the glaciers of Shackleton Inlet. Again from south of Minna Bluff, northwards to the Drygalski Ice Barrier Tongue, the general trend of the sastrugi is on the whole northerly. * It seems doubtful in view of the temperatures obtained by Shackleton near the South Pole, and Amundsen at the South Pole itself, whether 21:2° F. is not too high a figure for the mean temperature, reduced to sea level, of the South Pole in January. Possibly about 12° F. is a closer approximation. 7 The “ Encyclopedia Britannica,” 11th edition, vol. xxi. p. 970. DIRECTION OF PREVALENT WINDS 23 So far the winds follow the direction which they might be expected to take on the theory of streams of heavy cold air blowing spirally outwards down the slope of ce the inland ice from the summit of the main “ice divide.” The normal direction for such winds should, theoretically, in the latitude and neighbourhood of Ross Sea be from S.E. to N.W. or E.S.E. to W.N.W. There are four notable exceptions : First, the easterly winds at Framheim. A disturbing factor in the simple anticyclonic circulation is the warm gulf of Ross Sea, in considerable areas of which water is open throughout the year. This gulf encourages the further westerly deflection of the northerly moving air masses coming from off the land to the east of Ross Sea, and bends them around into easterly winds.* The next departure from the prevalent direction is in the case of the winds which blow out of Barne Inlet and Mulock Inlet on the west side of the Ross Barrier. These winds have a general W.S.W. to E.N.E. direction. They owe their direction probably to three factors : (1) A sag in the horst before it reaches that “ horst within a horst” the Royal Society Range. This allows the cold air of the plateau near the Britannia Range, dammed against the high bluffs and bastions of Mount Huggins, to spill over this sill in the horst, and stream into the low-pressure area of Ross Sea. This sag is further accentuated by deep inlets, the Barne and Mulock Inlets. (2) The steep isobaric as well as isothermal grade towards Ross Sea. (3) The general northerly movement of the Antarctic surface air from the Temperature Pole of the inland plateau. The next exception to the general rule is that of the plateau winds west of the Royal Society Range. These blow to E. by N., or E.N.E. into Ross Sea. Apparently they are in part responsible for the deflection of the steam column of Mount Erebus, which usually spreads away in an E. by N. to E.N.E. direction. The cold air from this plateau appears to flow down into Ross Sea, following the steepest grade which is also the shortest route to base level. Along the coast, from McMurdo Sound to the Reeves Glacier near Mount Nansen, the blizzard winds have a 8. to N. direction, blowing parallel to the steep western fault scarps of the great meridional horst. These blizzard sastrugi are crossed, opposite each of the outlet glaciers, by strong sastrugi trending nearly W. to E. and marking the direction of the plateau wind when it sweeps, often with hurricane force, through the portals of the glaciers of the western mountains down on to Ross Sea. The fourth exception, and a very remarkable one, is that of the winds between the coast near the Drygalski Barrier and the parting of the winds on the Magnetic Pole Plateau. * Amundsen gives the following percentage of his total number of wind observations: N. 19; N.E. 78; E. 31:9; S.E. 6:9; S. 12°3; S.W. 14:3; W. 2:6; N.W. 1:1; Calm, 21-3, Q4 METEOROLOGY These blow usually from about W.N.W. to E.S.E. Again, as in the case of the winds on the Barrier near Barne Inlet and Mulock Inlet, they owe their origin to the stemming action of the high portion of the Antarctic Horst known as the Admiralty Range. As shown on Plate V., the horst, as one passes from Mount Larsen (5000 feet), across the Reeves Glacier to Mount Nansen, jumps up suddenly in level from 5000 to over 8000 feet. Cold air flowing down the southerly slopes of this range overlooking the Reeves Glacier deflects the eastward-moving air masses flowing down to Ross Sea. These plateau winds in winter time must be of hurricane force, as they have torn out immense sastrugi in the hard snow of the Drygalski Barrier. Along the belt of inland firnfeld marked “ parting of the winds” on Plate VI. we found loose powdery snow devoid of sastrugi. This was the highest point on the Top of the Plateau, tae eee RS Te HE rl ing o' ne urface Winds WN.W. 70 N.W Winn oF THE GREA i? Cry > 155°IGE 727255 T POLAR CycLtone Magnetic Pole areas —_ J : ! ee ——- — > __ "4 2 a —- —_ $ __ ——_. Dense Snow Clouds” Ligne. snow, ) —~ a = NE Wind Wil é : trong & E Winds SE 13.105; : Dense Snow «Clouds ilkes pAnticnclone Ss 1D —————y -_—— Land? St 7 a) a Se W Plateay / MtNansen 8000F® Se. : ——— ice oO aleau ee, ee —— Inland snow and Reeves G] Lei Drygalski See Plateau Rocks (seen 8 909 by Shackletons Expedition) Iie, SX tee. acme! : arrier Sea Leve/ Kerry ———— ee ee Sel Aaa ales = = = = NW. Vertical Scale- 10000 feet to an Inch S.E. Fie. 5. SECTION ACROSS THE SOUTH MAGNETIC POLE PLATEAU Showing the parting of the surface winds on the plateau, and the probable nature of the atmospheric circulation and snow supply plateau on our line of traverse. It was 7350 feet above sea level. From thence, for 80 miles, to our furthest point N.W. the winds completely changed in direction, and blew chiefly in two directions forming two very definite and distinct types of sastrugi. The wind blowing from 8. by E., or 8.S.E., was evidently the normal anticyclonic blizzard wind blowing with great violence and ripping up the surface of the hard snow into sharp-edged sastrugi, three to four feet high. These were crossed by what we call ramp* sastrugi, as, being flat-topped, they formed miniature inclined planes, placed at an oblique angle to the other sastrugi, and so enabling us to sledge over what would otherwise have proved to be almost impassable snow ridges and furrows. + The foregoing figure (5) illustrates our view of the winds of the Magnetic Pole Plateau and the part they play in supplying snow to the plateau. * Ramp in a fort is defined as a road cut obliquely into, or added to, the interior slope of the rampart. } These ramp sastrugi seemed to us to be formed by the blizzard winds, as they slackened off, always hauling around to the east. As it swung around it gradually built these ramp sastrugi, which became flat- topped owing to the progressive swing of the wind direction from south to south-east. PREVALENT WINDS OF VICTORIA LAND 25 There are perhaps at least three possible sources of snow supply to the Ross Sea region of Antarctica. (1) Surface northerly to north-easterly or north-westerly winds sucked inland by the differential heating of the rocks of the Antarctic Horst and the adjacent snow- fields on the one hand as compared with the water of Ross Sea on the other. These may possibly be local extensions southwards of large cyclonic disturbances having their centres perhaps north of Ross Sea. (2) Local “endless belts” of air travelling seawards at night asa land breeze, and returning as a high-level (sometimes as a low-level) sea breeze during the day. These are illustrated on Fig. 5. (3) The great Antarctic high-level cylone overlying the permanent anticyclone. Some have doubted the existence of this cyclone, but from the fact that whenever there was an extra powerful eruption of Erebus, so that its steam cloud was carried to an altitude of about 20,000 feet, we invariably noticed that it was caught by a powerful W.N.W. or N.W. current, we are inclined to believe that this huge permanent cyclone really exists. It is to this source that the eminent Austrian meteorologist Dr. Julius Hann would refer most of the snow that falls far inland in Antarctica, following in this respect the German meteorologist Meinardus, whose fine memoir has shed so much light on atmospheric circulation in Antarctica. Hann quotes Meinardus* to this general effect : “These considerations will also do away with the difficulty of explaining the ice masses radiating away from the Antarctic Continent, for the centre of a great fixed anticyclone is not only poor in snowfall, but is rather a place of increased evaporation ; it is a region for starvation, not for alimentation of ice and glaciers. “But if cyclonic westerly winds extend into the higher altitudes ofthe Antarctic Continent, provision is made for the conveyance of vapour and for precipitation. Thus precipitation will not be wanting even in the interior of Antarctica.” Professor Hobbs in his “‘ Characteristics of Existing Glaciers ” has followed Hann’s views. We know very little about snowfall on the inland ice of Antarctica during the winter, but know something about the supply in summer. Snowfall. We may commence with the Magnetic Pole Plateau. As regards source of snow supply to this plateau, it is obvious that the prevalent winds depend, in part, for their direction upon the slope of the ground. The summit of the plateau has been termed on the map “ the parting of the winds,” and possibly it has actually in part been formed by the action of the winds. If the western winds perform more erosive work than the south-eastern upon equal quantities of annual snowfall, the divide will migrate westwards. If the reverse is the case, the divide will migrate south-eastwards. There can be no doubt that the original fall of the rocky plateau divided the position of the parting of movement of the inland snow and * «Handbuch der Klimatologie,” von Prof. Dr. J. Hann. Vol. iil. p. 689. 26 METEOROLOGY ice-fields in the first case, but after that the position of the surface divide would depend in part on the relative waste and supply effected by the prevalent winds. Near the Magnetic Polar area the great size of the sastrugi indicate winds of great violence. These probably blow most strongly in the winter time, or in late autumn and early spring, when the atmospheric gradient between the extra cold land and the still open sea would be steepest. Reference has already been made to the prevalence of the plateau wind, which is a land breeze on a large scale at night-time. When marching along the coast in October, November, and December of 1908, we found that the plateau wind reached the coast between about 8 p.m. and 10 p.m. and would go on blowing until about between 9 A.M. and 10 A.M. the following morning. It would usually freshen a little after midnight. Its usual speed appeared to be 12 to 15 miles an hour, scarcely sufficient to raise any drift snow, but with just sufficient speed to “sweep the carpet,” that is, drive the snow before it in a thin moving layer an inch or two deep over the surface of the sea ice. The immense sastrugi at the Drygalski Glacier show that towards winter the winds must blow from off the plateau with great fury, as already stated. It would seem as though the Ross Sea was the chief centre of low pressure. This would be due, of course, to its relatively warm water surface which is lightening the air above it, partly by warming, partly by supplying aqueous vapour to it. The cold airs to the south of Ross Sea rush into it from the south or south-east. The cold airs of the plateau stream into it from the west. It will thus be seen that the surface winds on the Magnetic Pole Plateau tend to blow radially outwards from the highest part of the plateau towards the sea, and at first sight do not seem likely to be bringers of snow. Whence then come the snows which feed the plateau? On December 27, from our position on the inland side of Mount Larsen, cumulus and alto-cumulus could be seen drifting inland from N.N.E. off the Ross Sea towards the 8.S.W., and at astill higher level the clouds were drifting inland from the N.E. Later on the same day, great rolls of alto-stratus could be seen drifting N.W. to about S.E. The rolls were strongly bent with their convexities directed towards the S.E. to E.S.E., as though they were being pushed over in this direction by a strong N.W. upper current. At Erebus, the normal downward limit of this current, which appeared very steady and constant there, was about 15,000 feet above sea level. Some additional light may be thrown on the snow supply of the Magnetic Pole Plateau, if we consider the conditions on the plateau west of the Ferrar Glacier. Here most of the snow which fell in November, according to Scott, came from a general S.W. by W. direction. On December 9, 1903, on the same plateau Scott records that there was evidence of a recent snowfall earlier that December, and that this December snowfall is far heavier on the edge than in the interior of the continent. He also states that the wind there in its most southerly PRECIPITATION Q7 direction brought a desirable increase of temperature, and on some days they had a fair imitation of the mild southerly blizzards which were such a conspicuous feature at the ship (7.e. at Hut Point, 8. end of Ross Island.—AvurHors). These observations suggest two possible sources of snow supply for the plateau W. of the Ferrar Glacier : (1) Moisture-laden air which has worked inland at a high level off the Ross Sea. The chilling of the air on the high plateau from below upwards makes the layers of air next the plateau surface denser than before, but in so doing necessarily with- draws material from the air above, and, consequently, sooner or later a height will be arrived at in the atmosphere overlying the plateau where the pressure is lower than it is for air at a corresponding altitude over the Ross Sea. Thus, while a surface air current, ‘the plateau wind,” blows down towards the sea and sweeps over Erebus in a current about 9000 to 10,000 feet deep between altitudes of 6000 feet and 15,000 feet, at a still higher altitude air will flow in to fill up the low pressure at high levels above the plateau. The air to replenish the cold masses which are continually gliding off the plateau can only be derived from the sea, and thus moisture, in other words, snow, is conveyed inland by what may be termed a high- level sea breeze. This movement of the atmosphere, of such importance for con- sidering snow supply in the Antarctic, is illustrated in Plate VI. The main source of supply of the moisture to the “high-level” sea breeze in the Antarctic is, of course, the Southern Ocean lying north of the main boundary of the continent. The main high-level sea breeze probably flows towards the “ Temperature Pole” (near the South Geographic Pole) in a grand high-level cyclone overlying the cold air masses which spiral out fitfully from the “Temperature Pole.” But Ross Sea, when open, sets up a secondary high-level anticyclonic area with its “low” situated over the plateau. Air flowing in from over Ross Sea towards the Magnetic Pole Plateau would have the trend of its current governed by the nearest areas of lower pressure in this upper atmosphere, and the lowest pressure at high atmospheric levels lies over the coldest land. On the Magnetic Pole Plateau the land is colder the further one proceeds south towards the “Temperature Pole.” Hence in this part of the Antarctic, near the west shore of Ross Sea, where the local high-level secondary cyclone perhaps dominates the main cyclone, one would expect the trend of the landward inflowing high-level air currents to assume a general N.E. to 8.W. direction. This was the observed direction of the inflowing high-level air currents near the coast side of the Magnetic Pole Plateau on December 27.* * On December 28, 1908, the weather was calm but very thick. At the surface of the plateau, later the same day, it was observed that a breeze from off the Ross Sea covered the top of Mount Nansen with cloud, but further inland this high-level breeze off the sea was deflected by the high-level N.W. air currents blowing from the South Ocean, Snow seemed to be falling heavily this day over the great horst to our east. We were at the time 20 miles west of the western side of the horst, and 50 miles distant from 28 METEOROLOGY We may return to the subject of the winds of the Magnetic Pole Plateau and the snow supply. It would appear that little snow falls on the centre of the plateau in summer time. During the five weeks that we were on the plateau, from December 25 to January 30, probably not more than one quarter of an inch of snow fell. The winds and their relation to snow supply on the Antarctic Plateau of the South Magnetic Pole Region may be summed up, very tentatively, as follows : 1. Anticyclonie winds, surface winds, mostly dry and cold, of two types : (a) The local surface plateau wind which parts at the summit of the Magnetic Pole Plateau into two air currents : (i) The W. by N. current blowing into Ross Sea. This is mostly a cold dry wind which does not produce snow on the plateau, but acts as a condenser and snow producer along the coast, where it meets the relatively warm, moist air over Ross Sea. (11) The 8. to 8.E. plateau wind blowing from off the summit of the plateau towards the Southern Ocean in the direction of Adélie Land. This brought a little snow with it, and probably represented the high-level N.W. cyclonic current which had dived as it became chilled inland, and then, after reaching the surface, became reversed. (>) The blizzard wind which forms part of a larger intermittent atmospheric circulation blowing spirally outwards from the ‘Temperature Pole,” or poles. Whereas on the west coast of Ross Sea the direction of the blizzard is nearly N. and S., on the edge of the plateau nearest the great horst it is about W. 30 8. This, it may be pointed out, agrees with Scott’s observation as to the direction of the blizzard wind on the plateau at the back of the Ferrar Glacier, viz. that it had more southing in it than the normal plateau wind. Although we experienced a plateau wind of the violence of a mild blizzard (about 25 miles an hour) on January 8, 1909, we did not encounter any violent blizzards at all on the Magnetic Pole Plateau on our journey between Dec. 24, 1908, and Jan. 30, 1909. 2. Cyclonic winds : (a) The local high level N.E. air current from off Ross Sea. This carries open water. Later the same day immense cloud pillars covered the top of Mount Larsen. On January 4, 1909, rolled cumulus spread fast over the Magnetic Pole Plateau coming from the N.W. towards the S.E., that is from the direction of the Southern Ocean near Adélie Land. This was over 100 miles inland from the Ross Sea. On January 5, 110 miles inland, the sky except to the S. and S.E., was thickly overcast with snow- clouds. The air at the surface was calm. These dense snow-clouds had evidently come in from the N.W., but, as this day was comparatively warm, they may have been added to by vapour derived from the sublimation of the snow surface of the plateau. On January 8 we experienced a blizzard with much low drift. It was of a mild order, and slackened towards evening. We have no record of fresh snow falling on this oc casion—apparently the drift snow was all old snow, but this is not certain. This was 140 miles inland, PRECIPITATION 29 snow-clouds in December and January for some distance inland. Probably when this system is accelerated, as it would be in autumn and winter, it may bring a great deal of snow to the eastern part of this plateau. (b) Cyclonic surface winds, portions of large cyclones N. of Ross Sea. (c) The N.W. high-level wind. This is part ofa vast circulation. As already stated, we observed it frequently rolling in great masses of snow-cloud as alto-cumulus, alto-stratus, and on one occasion apparently cumulus, from the N.W. This great air current is the one which supplies the “Temperature Pole” with air to replenish the supplies which have flowed away from it down-hill as blizzard winds, modified in places by local conditions of the physiographic relief of the plateau. There can be no doubt that when accelerated during spring or autumn, when the surface of the plateau is colder than on the occasion of our visit, it must bring quantities of snow with it to feed the inland Magnetic Pole Plateau, and even to take with it, as delicate ice needles, to the “Temperature Pole.” Thus the activity of great glaciers like the Reeves, Larsen, and David is probably due to this efficient double snowfall, the snow being partly derived from the northern part of Ross Sea, partly from the Southern Ocean, near Adélie Land. We may now glance briefly at the snow supplies of the King Edward VII. Plateau and the region near the South Pole itself. Scott and Amundsen have recorded that at the South Pole itself the snow is soft to a great depth, so that a tent pole could be thrust six feet into it, and in doing this no evidence whatever of any stratification was detected. Evidently, therefore, there is no very considerable sublimation and no thawing taking place at the South Pole, and on the whole the area cannot be much disturbed by winds. It appears to be the eye of the great anticyclone. Thin hazes, described as “a light fine vaporous curtain,” kept coming and going while Amundsen was at the South Pole from December 14—17.* Possibly these mists or hazes of ice crystals were derived from vapour sublimed from the surrounding snowfields, though, of course, it is equally possible that it may have been transported by the high-level cyclone all the way from the Southern Ocean. It is of great interest to note that from 80° 8. to 88° S. Amundsen met with new falling snow derived from surface winds. On November 27, 1911, just S. of 86° S. he encountered mist and snowfall, followed by dense fog and fine falling snow on November 28, the fog being described as ‘‘as thick as gruel.” From November 29 to December 3, a strong S.E. blizzard brought new-falling snow in lat. 86° 47/8. * “The South Pole,” vol. ii. p. 117. “ Often—very often indeed—on this part of the plateau, to the south of 88° 25’, we had difficulty in getting snow good enough—that is solid enough—for cutting blocks. The snow up here seemed to have fallen very quietly, in light breezes or calms. We could thrust the tent pole, which was 6 feet long, right down without meeting resistance, which showed that there was no hard layer of snow. The surface was perfectly level; there was not a sign of sastrugi in any direction.” 30 METEOROLOGY This remarkable blizzard reached King Edward VII. Land on December 1. The blizzard, with new-falling snow, continued to rage there until the morning of December 7. The same blizzard was experienced by Scott at the foot of the Beardmore Glacier, where it left 2 feet of new-fallen snow, as well as by Taylor and Debenham’s party at Granite Harbour to the north of McMurdo Sound; but Day, on the west side of the Barrier near 82° S., escaped this snowfall altogether. Nevertheless, practically the whole of the Ross Sea region was on this oceasion visited by the heavy snowfall. At Granite Harbour it was about 3 feet deep. One cannot but think that this remarkable snowfall, preceded by two days of winds blowing in sharp gusts from the north with dense fogs, was derived from moisture which had travelled inland, from the Ross Sea and the Southern Ocean beyond, as a surface wind, part of some large surface cyclone system, rather than that it was derived from the downward-diving air of the Antarctic high-level cyclone. Doubtless the fierce insolation to which the rocks and snowfields of the Antarctic Horst are subjected, as summer develops, was responsible for some of the vapour in the air. Amundsen relates (op. cit. vol. ii. p. 141) that on Christmas Eve, just north of 88° S., the surface of the snow, as the result of having been exposed to powerful sunshine was quite polished, and that near “Dog Depot” in 86° S., as seen on January 3, 1911, some of the snow beacons were found to be quite bent over, through the effect of the sun’s heat, and that ‘great icicles told us clearly enough how powerful the sunshine had been.” This interesting observation shows that snow can actually thaw, as already suggested, when exposed to long severe insolation, even when the shade temperature of the air in general, as distinct from the thin film next the snow, probably at no time rises to thaw point. “ Dog Depot” is 10,060 feet above sea level, so that the shade temperature at that latitude would probably not rise at all to thaw point. Close to the latitude of 84° S. cumulus was observed travelling from N. to 8. and at times from N.N.W. to 8.8.E., but this drift from the north was quite exceptional. Fresh-falling snow was recorded at 84° 35’ S. on the Beardmore Glacier, on December 14. For the whole of the previous day the surface wind had been N.E., and the cumulus had been drifting from E.N.E. This suggests that the moisture which formed this snow was derived from the Ross Sea or the Southern Ocean beyond it. S.W. or 8.S.W. winds always brought with them clear skies. If a great cyclonic wind were to dive at the Temperature Pole, it would surely retain some of its easterly component of movement and be a W.S.W., 8.W., or S.S.W. wind. J. B. Adams, of Shackleton’s expedition, describes the surface at latitude 88° 23’ S., longitude 162° E., as being formed of hard snow and hard sandy crystal drift. Summary. The question of snow supply to Antarctica is of course an extremely PRECIPITATION 31 complex question which can only be dealt with satisfactorily by able meteorologists.* Our impression at present is : (1) That ifa great permanent high-level cyclone exists it does not carry any very appreciable quantity of snow far inland, for if it did there would be far more fresh-falling snow than has actually been observed towards the middle and end of blizzards. (2) That the so-called permanent anticyclone of Antarctica is represented by a thin mass of cold stagnant air more or less concentric to the main Temperature Pole, in winter resting partly on the second Cold-Pole, discovered by Amundsen to the S. of “Framheim.” That this cold air mass does not radiate outwards continually and systematically, but is spasmodic and local in its outrushes, breaking away often a bit at a time, each unit rolling down separately to sea level as an independent air avalanche. (3) That such outrushes of cold air are partly replaced by a surface inflow, partly by an inflow at a high level, constituting for the time being a high-level polar cyclone. Probably, like the Polar cyclone, the high-level Polar cyclone is compound rather than simple. (4) That it is these surface currents moving Pole-wards that are responsible for the heaviest snowfall, at all events in summer. In winter when atmospheric circulation in general is accelerated in Antarctica the high-level air current, like that which passes over the Magnetic Pole Plateau, may contribute to the snowfall to a greater extent than it does in the summer. (5) Sea breezes in the Ross Sea, set up largely by the differential heating of the exposed rock masses of the Antarctic Horst as compared with the water surface of the Ross Sea, are responsible for a good deal of snowfall along the Western Mountains. (6) The surface relief of the land and the distribution of land and water have in many cases a paramount influence on the direction of the prevalent winds and consequently on the snowfall of Antarctica. ‘This is a fact which seems to stand out more clearly than any other in the meteorology of this region. Amount of Snowfall. Observations at Cape Royds showed that the snowfall of the year 1908 was approximately equal to about 9 inches (230 mm.) of rain. This estimate is approximately correct, but allowance must be made for the fact that it was extremely difficult to distinguish between old drift snow which found its way into the rain-gauge and new-falling snow. The result is intended to be an approximation of the amount of actual snowfall during the year. On the Great Ice Barrier in the latitude of Minna Bluff, 78° 45’8., the amount of snowfall is not known, but it was found that over 8 feet (2°4 m.) of snow had * Much fresh light will be thrown upon this problem when Dr. G. C. Simpson, the meteorologist to Captain Scott’s expedition of 1910-13, collates and publishes his unique records obtained in the Ross Sea region. 32 METEOROLOGY accumulated above Captain Scott's Depot A to the east of Minna Bluff, erected in 1902. This snow was found to be very hard and compact, and must have accumulated at the rate of about 13 inches (0°33 m.) per year. When thawed down it was found that these 13 inches were equal to 7} inches (188 mm.) of rain. The result, therefore, agrees fairly well with that obtained from the meteorological observations at Cape Royds. The snowfall at Cape Royds is somewhat heavier than that of the Great Ice Barrier, for the equivalent in snow of 7% inches of rain near Minna Bluff represents no doubt a great deal of drift snow as well as new-fallen snow. At the same time allowance must be made in the case of the Minna Bluff estimate for the removal of a certain amount of the snow by ablation. Ablation. The term “ Ablation” as used by Drygalski,* means the general lowering of the surface of ice, from whatever cause, except that of mechanical movement. It may thus be due to (1) Generation of ice-vapour direct, without actually the thawing of the ice surface ; (2) Generation of water-vapour from thaw water ; (3) Mechanical abrasion of an ice-surface by drifting snow or by rock-dust impelled by blizzard-winds. W. H. Hobbs? uses the term as synonymous with surface melting ; Chamberlin and Salisbury { speak of the evaporation and of the melting of ice, but do not use the term “ablation.” It will be used by us to denote a general lowering of the surface of the ice and snow from any of the three causes above specified ; but as our experiments were conducted in the Antarctic, in autumn, winter, and spring, at a temperature far below freezing-point, the most important factor to be considered was, no doubt, in this case, ice evaporation. Hann§ emphasizes the fact that the pressures of ice-vapour over ice and of water-vapour over water are different at similar temperatures. His Table is given in the foot-note below. Hobbs has pointed out (op. cit. pp. 162 and 176) the great importance of rock débris in bringing about the ablation of snow,|| In view of the fact that fine dust derived from rocks, mostly of dark colour, was widely distributed over the snow and ice at Cape Royds, where our experiments were carried out, what may be termed microscopic melting around minute dust-particles no doubt played an important part in the local ablation of ice and snow. * “ Grénland-Expedition,” “ Der Gesellschaft fiir Erdkunde, zu Berlin,’ 1891-1893, Berlin, 1897 (Band i. s. 541), where he renders Ablation, “Schwund der Hisoberflichen.” + “Characteristics of existing Glaciers,” New York, 1911, p. 162. ! + “Geology: Processes and their Results,” London, 1908, p. 279. § “Lehrbuch der Meteorologie,” Leipzig, 1906, s. 162. He there gives the following interesting Table: Temperatur . -—0 -2 -4 —6 -8 - 10 -12 -14 -16 Eis-dampf . 460 3:92 3°33 2°82 2°38 2-0 1:67 1:40 Ieiz/ Wasserdampf . 4°60 3°99 345 2°97 2°56 2°20 1:88 161 1°38 || He states that “for this purpose” (clearing the snow during the construction of the Bergen Railway in Norway, completed in December 1909) “covering the snow surface with fine dirt proved more effective than a corps of shovellers, the sun, in this case, performing the work.” ABLATION 33 Ablation at Cape Royds was measured by us in two ways. (1) By fixing bamboo poles into the lake ice, and marking on the pole the exact level of the ice-surface at the time the pole was fixed. Measurements, taken at intervals, showed that the surface was becoming progressively lowered. (2) Blocks of ice, approximately cubical, were cut from the ice of the lakes, and these were suspended in a position out of doors where sun and air had free access to them, and were weighed from time to time. We fixed a bamboo pole in the ice of Coast Lake, near the centre of the lake, on April 3, 1908. At the time this bamboo was fixed in position in the ice it was noticed that in many parts of the lake the delicate tips of the freshwater algze, so numerous in these lakes, projected about 2 inches above the surface of the ice. It is almost certain that the tips were about level with the surface of the water when the lake was first frozen over towards the end of summer. ‘That is, from about the beginning of February to the beginning of April, about 2 inches of ice had been ablated. On June 18, 1908, it was found, when the measurements were made from the mark on the bamboo pole at Coast Lake to the surface of the lake-ice, that 1°35 inches of ice had been ablated. It was a matter of great surprise to us that such a large amount of ablation had taken place during such a cold period, when the thermo- meter was mostly below 0° Fahr. At Pony Lake, close to our winter quarters at Cape Royds, the ablation was even greater. Dr. Mawson fixed a bamboo pole in the ice on this lake on April 18, and, on measuring it on June 12, found the amount of ablation to be 1:5 inches. That is, in the case of Coast Lake, 1°85 inches of ablation had taken place in seventy days, and, in the case of Pony Lake, 1°50 inches of ablation in fifty-five days. The bamboo pole at Coast Lake was measured again on June 20, 1908, when it showed only a little over 1°3 of an inch total ablation. A straight-edge, in the form of a light board with parallel sides, was used on this occasion, in order to ensure greater accuracy, as there seemed a slight tendency for the ice immediately around the base of the bamboo to be slightly lowered below the level of the surrounding ice. This reading is therefore perhaps more reliable than the one taken on June 13. It is hardly likely that the surface of the lake ice would have gained in height in the interval. On July 13 we fixed up another ablation- pole, this time in the ice of Blue Lake. On July 16 we fixed a second ablation- stick in Blue Lake. On July 22 we fixed another ablation-stake at Blue Lake, and also one at Clear Lake and one at Green Lake. On August 5 we measured the ablation-pole at Coast Lake, and the amount of ablation since April 3 was 1:9 inches. On October 2 we re-measured the bamboo pole at Coast Lake, and made out the total ablation to be about 1°63 inches, that is from April 3 until October 2. This seems inconsistent with the measurement, taken on August 5, of a total ablation already at that date of 1:9 inches, but it must be remembered that, in the intervals between the measurements, a good deal of snow had fallen and covered this lake, temporarily at any rate; and, in the second place, K 4 METEOROLOGY the surface of the lake was intersected with a network of cracks (see Fig. 54) and the fragments of ice between the cracks became slightly convex and tilted at various angles from the horizontal. Fortunately, this ablation can be checked by the observations made at the same time on the other stakes. Measurements on October 2 showed that, at Blue Lake, the ablation since July 16 had been about °42 of an inch, at Green Lake °25 of an inch, and at Clear Lake ‘33 of an inch. It may be mentioned that the ice of Blue Lake and of Clear Lake was practically fresh, while that of Green Lake was saline. Blue Lake, as being a large expanse, and having, at the point where the stake was fixed, a smooth and but slightly cracked surface, may be taken as giving a reliable figure for the ablation between July 16 and October 2; that is about -0054 of an inch per day—or 42 inches for seventy-eight days. Had the ablation at Coast Lake continued at 1°9 inches (the amount measured on August 5) from June 20 to October 2, 118 days, the rate of ablation would, practically, have been the same as for Blue Lake, viz. ‘0053 inches per day. We may conclude that the ablation due chiefly to evaporation of ice-vapour and water-vapour, was, in 1908, at Cape Royds, equal to about 2 inches from April 3 to October 2—a period of 150 days. This evaporation was probably, for the most part, due to generation of ice-vapour, possibly in part to the formation of water-vapour from microscopic thawing around dust-particles, at a time when the general temperature was still far below freeziug-point. This amount of ablation due to evaporation alone is truly surprising, especially when one reflects that from April 23 until August 22 the sun was continually below the horizon. Thus one can easily credit the evidence of ablation, already alluded to, afforded by the distance to which the tips of the freshwater algze were found to project above the surface of the lake-ice on April 3, viz. that about 2 imches of ablation, due chiefly to evaporation, had taken place already between the beginning of February and April 3.* This would make the total amount of ice-ablation about 4 inches from February to October. It remains to be seen what amount of ablation due to evaporation takes place during October and November, December and January. If another 3 inches disappears, then this will make the total evaporation 7 inches, which will about account for nearly all the precipitation in that part of the Antarctic. The annual precipitation at Cape Royds, in 1908, was probably equal to about 93 inches of rain. The precipitation was entirely in the form of snow. It must also be remembered that, in December and January, the ice and snow suffer a considerable amount of ablation, not only through evaporation of ice and thaw water, but also through the running off of the thaw water. * The alga being very flexible and flaccid during the summer thaw, its tips would not project above the general level of the thaw water of the lakes as long as the water remained unfrozen. Thus the tips would begin to be left in relief only after the date of the final freezing of the lake at the end of the summer. ABLATION 35 These ablation results are not very different from the evaporation observations made by the Discovery Expedition.* In these experiments three shallow dishes were employed, giving areas respectively of 12, 12, and 24 square inches. These were filled with water, which was allowed to freeze, and then the dishes were placed on the meteorological screen. The dish and ice were weighed day by day, and the difference between two consecutive weights gave the loss by evaporation. From March to October inclusive, in 1903, the total evaporation amounted to 2°910 inches, and the evaporation for November of the previous year amounted to 0°702 of an inch. If this be added to the previous amount the evaporation for the nine months from March to November would be 3°612 inches. The amount of evapora- tion for December, January, and February is wanting, but it appears to one of us (Professor David) that the amount would have been of the order of *8 inch per month. In this case the total annual evaporation would have been about 2:4+43°612=in round numbers about 6 inches. It will be noted that in the case of our experiments we employed actual lake surfaces instead of dishes, and that occasionally the lake surfaces were temporarily snowed over. In most cases, however, the snow covering was quickly dusted off them by strong winds, except in the case of Clear Lake, where there was evidence of some irregular lumpy structure developing on the previous even surface of the ice some time subsequent to snowstorms. Probably the estimate given of 7 inches as the total annual evaporation at Cape Royds (irrespective of the ice and snow that are lost by actual thawing through heat radiated from sun-warmed rocks) is not an over-estimate. This great amount of loss of ice by evaporation is, no doubt, due (1) to the extreme dryness of the air ; (2) to the consequent intensity of solar radiation ; (3) to the speed of the blizzard winds. This immense evaporation is obviously a fact of the first importance in studying the glaciology of Antarctica, especially when the additional point is borne in mind (and this point cannot be too strongly emphasized) that probably at least 95 per cent. of the surface of Antarctica is covered superficially not with ice but with snow. The great surface offered by snow spicules and flakes in proportion to their volume would greatly accelerate the rate of the evaporation and so increase its amount. For example, we noticed the tracks of sledges or footprints in the snow within a few weeks were left strongly in relief. This may have been in part a mechanical “survival of the fittest,” that is, the compressed snow may have resisted the mechanical force of the blizzards better than the loose snow. Spiracle Ice or Moss Ice. Another evidence of ice evaporation is to be found in what may be termed spiracle ice. Dr. Mackay first called attention to this on the journey to the South Magnetic Pole area, when the party was crossing the Drygalski Ice Barrier Tongue. This glacier was heavily crevassed, and here and there were to * “National Antarctic Expedition,” 1901-4. “‘ Meteorology,” pt. i. published by the Royal Society, London, 1908, pp, 11 and 473-475. 36 METEOROLOGY be seen low rounded clumps of pure white needle-like ice crystals of plano-convex shape, with the convexity uppermost. These masses were from a few inches to a foot or so in diameter, and from a few inches to about 6 inches thick. Their appearance was somewhat as follows : left wall LOifERE ta Ne, span ee AON & : Right wall yy SSS ; of crevasse. \\ Bera ieee aes ater a or Hay, qj révasse S Solid Ice \ =N3 Open crevasse 4 4,0 Seg ip ob oO Loy with probably a Ji Byauo 5 o GOT Sea water at Nip > op about 250feeE yeh below. Sree mS w 7 S = < \ AN Xx \ Fic. 6. MOSS ICE OR SPIRACLE ICE Formed by crystallisation of vapour, from sea water at bottom of crevasse, transpired through snow lid of crevasse We crossed the Drygalski Barrier early in December, and this spiracle ice was obviously of quite recent growth. The crystals evidently developed at spots where the lid of the crevasse was so thin as to be capable of being used as arespirator. Air would alternately filter into or filter out of the crevasses through these “ respirators,” beautiful vertical needles of ice growing upwards from the upper side and downwards from the lower sides of the respirator. The probable explanation of these tufts of moss ice is that on this part of the Drygalski Barrier the lower portion of the crevasse may reach down to sea-level, and even be filled with sea water, or, at all events, have a temperature near the freezing-point of sea water. Thus the relatively warm vapour would rise from below and be chilled higher up in the crevasse with deposition of ice needles on the walls and at respirators. At “ Priestley Shaft” at the Blue Lake, Cape Royds, a similar phenomenon was observed. The vapour from next the bottom of the lake formed ice crystals on the walls of the upper part of the shaft. In part this moss ice may be due to convection currents under the lid of the crevasse, due to differential solar heating; but the former hypothesis seems more probable. That an appreciable amount of vapour is present in Antarctic crevasses is proved by the fact that in summer, at all events, from near Mount Nansen SNOW-CRUSTS 37 on the north to Beardmore Glacier on the south they are lined with delicate ice crystals. Pie-crust Snow. Another phenomenon due to ablation is what may be termed Pie-crust Snow. The surface of the snow under the influence of the direct rays of the sun in a cloudless sky becomes alternately softened by microscopic thaw around dust particles, and again, as temperature falls towards midnight, it becomes hardened by re-freezing. Such pie-crust surfaces were met with notably on the sea ice on the journey from Cape Royds to the head of the Farrar Glacier, on the Great Ice Barrier, and on the Drygalski Glacier. They were distressing to sledgers, for one’s feet would break through the tough crust at every step, and sink some 4 to 6 inches into loose powdery snow beneath, and each time one’s foot was pulled out the toe of the ski boot or finnesko would tear away a piece of the crust with it. This structure was perhaps best developed in the snow covering the sea ice. Different stages of its formation were specially studied by one of us (R. E. Priestley) on the western journey when travelling over the snow-drifted surface of the sea ice of McMurdo Sound. At first a fine glazed surface became developed on the northern end of the sastrugi, due to the heat of the sun on the drifts when the sun is to the north of them, as it is by day, and the freezing action when the sun’s heat is lessened, towards midnight during the season of midnight sun in December. At the time these observations were made, between December 14 and January 6, no corre- sponding glazing took place on the southern side of the sastrugi, owing, of course, to the diminished intensity of solar radiation when the sun was in the south. On flat surfaces, however, this glazing process affected extensive areas. On January 26 the snow crust formed by the heat of the sun was strongly in evidence, and was evidently continuous over large areas. It was poised so delicately that when one set foot on the edge of such an area the whole patch, sometimes a hundred or more square yards in area, fell in with a long-drawn sibilant sound, which resembled nothing so much as the noise made by the falling of heavy hoar-frost from a tree when the branches are beaten by a stick. Below this surface crust the snow is loose and powdery, and often shows incipient traces of granulation. For example, the snow on the south side of the Nordenskjéld Ice Barrier Tongue, on November 11, 1908, showed the section (Fig. 7) on page 38. Again, at the S.W. end of McMurdo Sound it was observed that adjacent to the “pinnacled ice” was sea ice three or four years old. Its surface was three or four feet above sea ievel, but less than two feet of the portion above sea level appears to be ice. It seems probable that the whole thickness is not more than 15 to 16 feet. It was covered with drift snow. The older drifts were not quite sufficiently hard to bear the weight of a man, and at every step one dropped eight or nine inches on to a firmer surface. The space between the two crusts was filled with a coarse- grained snow powder, due to a selective action of the thaw and evaporation, those 38 METEOROLOGY ice erystals or ice grains which were left having increased in size at the expense of the grains which had been partly vaporised, partly absorbed, while thawing, to swell the volume of the larger granular crystals. Underneath this eight or nine Feet. Inches. PEREGO a Q-- J Fine grained white hard snow. 1» | Snow showing development of névé crystals becoming successively larger downwards. There ts 2 considerable amount of interstitial air space due in part to sublimation inpart to closer packing oF the névé crystals below which thus leave open air spaces above them. Ae EARS - ote & “co 6 @ 84:62 Veer soe: Ons Cove © 6 © Ice crystals, developed out of the snow, found next to the sea ice just south of \ Nordenskjold (ce Barrier Tongue. © Natural size. Fic. 7, SKETCH SHOWING EFFECT OF SUBLIMATION ON SNOW OVERLYING SEA ICE NEAR NORDENSKJOLD ICE BARRIER inches of crust snow and ice granules was an older surface of crust snow. The structure of the whole is illustrated in Fig. 8. It seems probable that the formation of this crust snow is somewhat in this way :—The sun on bright clear days warms the air above the snow and even in the interstices between the snow grains for some little depth down.* Consequently evaporation during the warmer part of the day becomes very rapid, chiefly at the surface of the snow, but also penetrating to a depth of several inches. In cases where the snow seldom actually thaws, as on the vast névé fields of the high inland plateau, little but waste of the snow surface takes place during the warmer parts of the day; but as the surface temperature falls at night the ice vapour still rising from the interstices between the snow crystals beneath the surface is deposited in a solid form on the snow crystals at or near the surface, and so tends * That the sun’s heat passes rapidly through a considerable thickness of ice, is abundantly shown by the temperatures taken by us in shafts sunk through the lake ice of Cape Royds, as explained elsewhere in this memoir. Its penetration through snow would no doubt be much slower. Unfortunately we did not onduct any experiments on this subject. SNOW-CRUSTS 39 to cement them together. This carrying up of ice-vapour from below to enrich the surface in ice somewhat resembles the feature of the surface caking of garden soils, if left for some time undisturbed. In the latter case the caking is the result chiefly of Feet Inches ——— O ~ J (about) Hard crust snow. 0 - 8 Loosely coherent granular ice crystals. O - | Hard crust snow of older drift. 7 ery SO eae « Ca CCA CIS 2 (about). Probably loosely coherent granular Ice crystals. Surface af ald séa ice, probaly 3 to4years old and abaut 15 tol6 feet thick. Fie, 8. SKETCH SHOWING EFFECT OF SUBLIMATION AND THAWING UPON SNOW NEAR “ PINNACLED ICE” OF McMURDO SOUND water, ascending by capillarity, and carrying mineral matter dissolved in it, depositing that mineral matter at the surface of the ground when the water evapo- rates. In the case of the Antarctic snowfields the crust is formed, not by ceapillarity, where there is no thaw, but by ascent of relatively warmer ice-vapour coming in contact with the cold air at night above the snow surface. Where snow crusts develop on snow-drifts near sea level the hardening of the surface is much facilitated by actual thawing, and it is even possible then that capillarity may assist in conveying thaw water up to the snow surface. On very hot days evaporation proceeds so rapidly that it completely removes the harder top crust, and sets free at the surface the granular ice crystals originally formed beneath the surface. Shackleton states in regard to the snow surface over which the Southern party travelled on the high plateau (from 7000 feet to over 10,000 feet above sea level) to the south of the Beardmore Glacier: “Still further south we kept breaking through a hard crust that underlay the soft surface snow, and we then sank in about 8 inches. This surface, which made the marching heavy, continued to the point at which we planted the flag.” * Again Shackleton describes the crust snow on the surface of the Great Ice Barrier (op. cit. 12): ‘ After we had passed latitude 80° S., the snow got softer day by day, and the ponies would often break through the upper crust, and sink in right * “ Heart of the Antarctic,” vol. 11. p. 18. 40 ME'TEOROLOGY up to their bellies. When the sun was hot the travelling would be much better, for the surface snow got near the melting-point, and formed a slippery layer not easily broken. Then again a fall in the temperature would produce a thin crust through which one broke very easily.” * On consulting the thermometer readings of the Southern party, we find that the highest temperatures recorded for their journey over the Great Ice Barrier were 22° Fahr. at 8 a.m. on December 3, 1908, and 21° Fahr. at 1 P.M. on December 2. The shade temperature for noon on December 3 was not taken. On December 2 the shade temperature at 8 A.M. was 14° Fahr. There was a rise there- fore on December 2 of 7° Fahr. between 8 a.m. and 1 p.m. If there was a similar rise in temperature on December 38, the shade temperature on that day may have been about 29° Fahr. at 1 p.m. December 3 was the last day of the Southern party’s journey over the Great Ice Barrier. Previous to these two days the shade temperature had been considerably below freezing-point. It was probably the case that the softening of the snow surface, described by Shackleton as preceding the formation of the crust on the snow surface, was due to actual microscopic thawing partly caused by minute particles of rock dust, spread over the snow by the blizzards. Granular Ice Crystals from Snow. On relatively warm bright days in summer it seemed as though crops of granular ice crystals were growing on the surface of the snow. On the Barrier near latitude 83° 16’ 8., Shackleton states :* ‘The surface of the Barrier still sparkles with the million frozen crystals which stand apart from the ordinary surface snow.” Again (op. cit. vol. 11. p. 12) he says, speaking of the surface of the barrier: ‘‘ The snow generally was dry and powdery, but some of the crystals were large, and show in reflected light all the million colours of diamonds.” At an altitude of over 7000 feet on the plateau on which the South Magnetic Pole is situated, these crystals are much in evidence. These ice crystals on January 14, 1909, were found to be about half an inch in width and about one sixteenth of an inch in thickness. They form a layer about half an inch in thickness over the top of the névé. In the bright sunlight the snow surface covered with these sheets of bright reflecting ice crystals glitters like a sea of diamonds. Probably these crystals were not being freshly developed each sunny day at the surface of the snow, but were crystals originally formed an inch or so below the snow surface and subsequently exposed through the removal of the former covering by evaporation. If this is so, their presence shows that there is considerable evaporation taking place on these high Antarctic plateaux. The snow surface of this plateau was never up to thaw point, and almost certainly never is. The hottest temperature that the Northern party experienced on the part of the plateau near to the Magnetic Pole area, where the above observation was made, was about 15° Fahr.¢ on the noon of January 5, 1909, at an altitude of about 7000 * “The Heart of the Antarctic,” vol. i. p. 308. + Not corrected for instrumental error. PRECIPITATION 41 feet. The plateau here is also practically free from rock dust. It may therefore be questioned whether even near the summer solstice the temperature there rises to thaw point. There can be no doubt that these large ice crystals, where they are developed on the higher plateaux, are formed by a process of vaporisation and recrystallisation at a temperature considerably below freezing-point. Near sea level granulation below the snow surface is to be attributed to partial thaw in many instances as well as to vaporisation. As granulation is of course much more active in summer than in winter, the drift brought up by a blizzard in summer consists largely of finely granulated snow. This fact was specially experienced and noted by the Western party. They found that in summer the drift snow on the sea ice of McMurdo Sound was composed in its upper portion of loosely coherent granular snow, the individual grains being much larger than those accompanying the winter drifts. It was from such snow that the largest quantity of the low-flying drift was derived which accompanied the southerly gale of December 7, 8, 9 of 1908. It was a distinctive feature of the summer blizzards, experienced during the Western journey, as opposed to the winter ones experienced at Cape Royds, that the drift accompanying them was always low-flying and heavy, and if it did reach as high as the face—a most unusual thing—it felt like fine gravel. This is no doubt due to the thawing action of the sun on the freshly fallen snow lying on the sea ice and glacier surfaces. On January 2 the Western party observed a curious type of hvar-frost precipitation from water-vapour or ice-vapour—which is described as follows in the diary of one of us (R. E. Priestley) : “On January 2 a new type of precipitation was observed, and one so unusual that we have noted it as follows : “Yesterday and the day before, this part of the Sound was traversed by a layer of moisture-laden air moving slowly towards the north-west. To-day the snow and ice are covered by little snow-trees about an inch to an inch anda half high, and consisting of a central axis with six branches, three short ones to leeward separated from each other by a very acute angle, and these in turn separated by an obtuse angle from three long branches, similarly disposed, to windward. These branches were directed upwards at an angle of 30°, and as both they and the central axis increased in size as the height above the ground increased, the resulting structure looked decidedly top-heavy. Sometimes the trees were compound, having several other single main axes with their six branches of exactly similar appearance, except that the branches on those axes nearly at right angles to the stem were of equal length on either side. “These peculiar ‘trees’ seem to be due to an accretionary growth of ice from the moisture in the air, but the most interesting point about them was undoubtedly their singularly symmetrical form.” Ice Flowers. Somewhat analogous in their origin are the ice flowers. The . 42 METEOROLOGY condition most favourable for thei growth appeared to be a sudden fall of temperature during an interval of calm weather, just after a blizzard had stripped the ice off the sea. The finest development of ice flowers, shown on Plate VII., Fig. 2, took place on March 20, 1908. The ice under the ice flowers on March 20 was about 3 inches in thickness, and, though tough, bent very much under a man’s weight. The meteorological conditions which led up to the development of these “ March 8 there was a very violent blizzard which drove out practically all the ice which had formed on McMurdo Sound. On March 11 there was a light gale from S.E. threatening to develop into a blizzard and keeping the sea ice-free. The wind ice flowers” were the following :—On continued mostly from the $.E. The temperature was continually falling, and on March 16 the sea, which was now much warmer than the air (about 20° Fahr. as compared with 6°3° Fahr.), was covered with steam or frost smoke, as though it had been boiling (see Fig. 1, Plate VII.). On March 18, 19, and 20 the weather was calm, and, with a mean air temperature on March 19 of — 8°9° Fahr., the sea surface froze over very rapidly, and a splendid crop of ice flowers developed (see Fig. 2, Plate VIL). On that afternoon about half an inch of snow fell. The following day the temperature fell further, then rose again on March 24, 25, and 26, reaching a few degrees above zero Fahr. On March 27, at a temperature of 1°50° Fahr., all that remained of the ice flowers were miniature domes of snow about 14 inches high and 2 inches wide. These were pierced by slits where the plates of the crystals had been dissolved out. Lying around the bases of these domes and pointing outwards radially, were the still frozen edges and tips of the plates, the petals, as it were, of the flower. These being formed of pure ice derived from the frost smoke had remained frozen, while the centre of the flower, formed of various cryo-hydrates, had melted away. Thus under the centre of each dome was a tiny pool of bitter saline water. Dr. Mawson has thus explained the origin of these ice flowers : “ During the formation of the surface ice some of the sea salts are squeezed upwards through capillary cracks to the surface, and there in the form of concentrated brine eventually freeze as cryo-hydrates and form nuclei for additions from atmospheric vapour. The net result is the production of little rosette-shaped aggregates of radiating crystal blades, which were met with up to 2 inches in height.” * We also observed ice flowers, as Murray has already recorded (op. cit. p. 341) on the freshwater ice of Clear Lake and Blue Lake near Cape Royds. ‘They were on the ice rapidly and tranquilly formed in the trenches sunk for the observation of temperature. They were much smaller than those on the sea ice, being only half an inch or less in diameter.” Bund Structure in Sea Ice. Another phenomenon due to freezing of vapour is the raising of the edges of ice-floes through the freezing of vapour rising from the sea * “ Heart of the Antarctic,” vol. ii. p. 337. PLATE VII Fie. 1. FROST SMOKE RISING FROM THE SEA After young sea ice has been broken up by blizzard, MeMurdo Sound, March 16, 1908 | Photo by David Fic, 2. ICE FLOWERS ON SEA ICE McMurdo Sound, March 28, 1908. The centres of the clusters are formed of the cryo-hydrates of sea water. The edges are formed of ice of the nature of hoar-frost. [Photo by Shackleton [To face p. 42 PLATE VIII ANUVA AdVO UVAN “(THAAT VAS MOTEA LEGA 81 AOVAAS GOl) A4V1 MNOS SSOYUDV NOLLOWS $2.93 08 09 Ov co ) SaujzaW Ozi oot og 09 Ov o2 OF Oo A aha Se es ee ee oe 5 "Joa4 052 con Py! 00) 0s 0) 91293 |B91940/ suey) 9 S v € 2 1 a Oj299 |2QU0ZI0OK ‘auteg ade) 4eau‘janaj Rag Mo}aq 3aay B) a2eJINS ad1’aye] YUNG Ssos2e UOIQJ—ag ° “9 Pa% a5 % 8 ai iis 22/8389 300) a0/ en Rascal a ano) pes Aidt a ay 2) \ \ h ne uae ‘INN MSs SHG) B9Kiay, dears Wifi essa ve DET OTT Da. a) Ee ca Re LOL "SNIWH) JO AIvIG AMV] MNNS Ui PRU CEN ea ae Ani wnnsovpysreanne a ‘rosso (sens rem 44 METEOROLOGY beneath, on the walls of the ice-floes, raising them slightly at their edges, reminding one of the little mud walls or bunds raised by the agriculturists of India and Ceylon to impound water in their rice-fields. The sea ice there was repeatedly cracked by the heaving of the sea outside the bay during blizzards. Thus while the edges of the floes touched, the cracks between them were kept open, so that vapour was continually steaming up from below. These little walls of circumvallation, from 4 to 6 inches high, are not to be confounded with the upturned edges of thin ice floes, the upturning being due to constant collision’ while the ice at the edge of the floe was in actual process of growth. In reference to the relation between precipitation in general, in the Ross region of Antarctica, and ablation,* what appears to us to be an exceedingly important piece of evidence is afforded by Sunk Lake near Cape Barne. In the case of very numerous small lakes, near Cape Royds, there is fair evidence of recent and still existing conditions of desiccation. These either still exist amongst the moraines or ice-scooped rock hollows on the western flanks of Erebus, some showing traces of old terraces now considerably above their present water level, or have dried up completely, leaving only old shore lines fringed with algal peat and diatomaceous mud to tell of their former presence. Nevertheless, as much of this morainic material at a depth rests on ice, and this ice is from time to time thawing and so causing the morainic material above it to slowly subside, it might be argued that some, at any rate, of these lake hollows have become dry through a process of draining rather than through evaporation exceeding precipitation. + No such explanation, however, will apply to Sunk Lake, which is shown on Plate VIII. Its ice surface is 18 feet below sea level in spite of the fact that it is only about 70 yards from the sea to the nearest point of the lake. The lake is certainly wind-swept, so that very little snow lies upon it; at the same time it is well supplied with snow-drifts, which during the season of thaw contribute a good deal of thaw water to the lake. On the whole this lake may be regarded as a large rain-gauge, and the fact that its ice surface is so far below sea level appears to us to bear most important testimony to the fact that at present in this part of Antarctica ablation, in this case due chiefly to evaporation, exceeds precipitation. * Ablation is here used in the widest sense, to comprise all the natural processes which lead to the removal of a surface of snow or ice, whether upper or under surface, and includes the processes of sublima- tion, surface thawing and melting at the base, removal of snow by wind as well as loss by wind abrasion, and also loss through the breaking away of bergs. + The ice under these old moraines is probably fossil ice left by the former Ross Barrier when at its maximum extension. CHAPTER III DYNAMIC GEOLOGY (continued) PART II. GLACIOLOGY Dr. Mawson, Mineralogist, Chemist, and Physicist to our Expedition, proposes to deal with the subject of Antarctic ice as a mineral, with special reference to granulation, crystallisation, &¢. We propose to divide this subject into land ice and sea ice. In the matter of land ice we adopt H. T. Ferrar’s classification,* who in turn has followed Drygalski,t Heim, { H. Rink, § Arctowski, || and Gourdon.{ We divide the different type developments of land ice as follows :— 1. Inland Ice. 2. Ice Caps (Calottes, Hochlandezvs). 3. Piedmont Glaciers (Glaciers plats and Glaciers cétiéres). (a) Piedmonts on land. (b) Piedmonts aground. (c) Piedmonts afloat. 4. Glaciers of Greenland type, usually termed by us Outlet Glaciers or Spillway Glaciers. Glaciers of Norwegian type, flowing down defined valleys from large firnfeld. Glaciers of Alpine type (Glaciers encaissés). These drain small basins only. Cliff Glaciers. Reconstructed (recemented) Glaciers. . Hanging Glaciers. Corrie Glaciers, Cwm Glaciers, Cirques (Kare). . Ice-slabs. These remarkable stagnant masses of glacier ice, without visible means of subsistence except to a limited extent from drift snows, are considered by Ferrar to be peculiar to the Antarctic. They are either “beheaded” glaciers which have lost their firnfeld, or are dune glaciers formed in the lee of high mountains along the coastal strip.** 11. Icebergs. 12. Lake Ice. * Nat. Ant. Ex., 1901-4. Geology, p. 63. 7 “Gronland Expedition,” 1897. { Handbuch der Gletcherkunde. § Danish Greenland, 1877. || Expédition Antarctique Belge. Géologie—Les Glaciers, 1897-99. {| Expédition Antarctique Frangaise, 1903-5, Charcot.—Glaciologie, Gourdon. Also “Le Pourquoi-Pas? dans |’Antaretique,” 1908-9. Charcot. ** Similar glaciers are described from Alaska by 8, K. Gilbert, Records of the Harriman Alaska Expedition, vol. iii., “ Glaciers.” SHON AS 45 G 46 GLACIOLOGY As Mr. Griffith Taylor, Senior Geologist to the late Captain R. F. Scott’s Expedition, has made recently a special study of the Antarctic cirques, we omit more than passing reference to them in this Memoir. Icebergs will be described under sea ice, in which we include all fragments of floating ice, as well as fast ice. We may now pass on to consider the glaciers of the Antarctic Horst in detail, commencing with the northernmost group examined by us, the Drygalski-Reeves Piedmont.* Reference to the map (Plate IX.) shows that each of these three glaciers is of the “outlet glacier” type, that is, they are ice canals draining vast inland ice-fields, and resemble the glaciers of the west coast of Greenland. The ice in excess of that which is held by frictional resistance moves under gravity and other causes through the channels of the Reeves, the Larsen, and Drygalski and other glaciers into Ross Sea. These glaciers preserve their individuality only where they cross the great horst. To its west they are united in the vast inland snow-fields and underlying ice-fields, while on the coast to the east the Larsen Glacier is united in the form of an “ice-apron,” or piedmont afloat, to the Drygalski Tongue, which passes inland into the David Glacier. The united Drygalski and Larsen ice-aprons almost coalesce on the north side of the Larsen Piedmont with that of the Reeves Glacier. Formerly during the period of maximum glaciation all three must have not only been united together, but were also joined along the coast to the Davis Glacier, the Cheetham Ice Tongue, the Harbord Ice Tongue, the Mawson Glacier with the Cotton Glacier, the Nordenskjéld Tongue, the Fry Glacier, the Penck Glacier, the Mackay Glacier, and the Ferrar Glacier. As the last mentioned glacier was formerly united to the ice of the great Ice Barrier —it was probably so united in Sir James C. Ross’ time in 1840-42—we may conclude that that gigantic piedmont afloat was formerly continuous to at least as far north as Evans Coves, if not to the north side of Terra Nova Bay near Cape Washington. All trace of the great continuous piedmont ceases just before Cape Washington is reached. The high steep-to character of the coast at Cape Washington, with absence of the usual coast platform, is shown in Figs. 1 and 2 of the Physiographic Chapter. There can be little doubt that, during the maximum glaciation, the whole coast and south-west part of Ross Sea, from Cape Bird on the south to Cape Washington on the north, was filled with ice. This would give the Ross Barrier an extension of about 220 miles northwards of its present northerly limit, so that during the maximum glaciation the Ross Barrier had a total length of perhaps 700 miles. In some sense then, in dealing with the Reeves, Larsen, and David Glaciers, we are dealing with the now shrunken former tributaries of the Ross Barrier. By * The following descriptions of the glaciers of this region are based on the observations of the Magnetic Pole Party—Professor David, Mawson, and Mackay. LOIN] daaq 10 HLUON ONIAT GNV SaN01) HLIM daddvVo0 AUNUNONTAW LNOOW GONVIL -BIG ATOGIW NI SAAOD SNVATL LAIN adaq Nasuv'yT INNOW GHOVIHaAy INOOW ie LARSEN- E. David, redrawn b HOWING THE DRYGALSKI WwW . Sketch by T ) miles. [ To face p. 46 Mowry Howane Davi Guscime WUeviuuwe Wane Moesy ecives PANORAMA ILLUSTRATING NORTHERN PARTY'S JOURNEY, The distance from Evan: Mocs Geaacnx Mowsy L Macey Naveen ND SHOWING THE DIRYGALSKI-LARSEN-REEVES PIEDMONT IN FOREGROUND Joven to ’Urville's Wall is 4S miles. Sketch by T, W. E. David, redrawn by George Marston Deer tava vase Cores ve wineue our Mowre Mataowese Carre ‘srr Chores ase Urine fourm or Deny ture [To face p46 PLATE IX Wood M:Mackintos M* Melbourne 8337 lel 1 2. - ee ol G g Numerous ne —— 1 z ) e mes ZB “Ss i eee ; os 0, 30.12.08. ee acer 35 Gerlache = iS f:, 8000 Inlet = LS ; C.Washington ANG Le ae Pa SO CBI2UB = OS OG Q a : oan ee ’ 3540*o. / ) 2 29.109. °<%, 27 12.08 2 oe ON g gz Se ‘ " 3 < 2800'n, os, Terra Nova 752) wal 30./.09.\% ant 98 9,19.1208 Evans Coves. 2) a ]” \... Cracks containing} sea water y Pee Bay ‘Ice Donga, ~~\\ cy COMP, \ i 2 BARRIER \ Z rd) eri AG Ae f Inlet z / , ’ Caos 3.2.09> Is. ee 7 CLACIER yk mee A) |, DRYGALSKI \. ICE BARRIER eee ‘12.08 ‘TONGUE 270% + 300 fathoms it : Scale of S' ratuke M iles 6 ao ‘ PRIOR i= pe CHEETHAM ICE BARRIER TONGUE ' ' ' ' ' ' ' ' ' ‘ ' 4 ' ' ‘ ‘ . GRE TZ} 164° Map of Nansen -Drygalski area of South Victoria Land Showing Coast, Horst, outlet Glaciers, & Inland Ice. Chiefly after Survey byDrMawson. 48 GLACIOLOGY a process of betrunking, such as rivers suffer through coastal submergence, but which is due in this case to deglaciation, the old ice drainage has become disinte- grated and all these glaciers have become dismembered, with the exception perhaps of the three with which we are now dealing,* and even of these three the Reeves Glacier is all but, if not quite, dismembered from the Larsen-Drygalski Piedmont. The doubt in regard to this question of the exact line of demarcation, if any, between the Reeves Piedmont and the Larsen Piedmont, is due to the fact that at their margins each apron seems to pass gradually into old sea ice laden with the snowfalls of many years. It is hard to say where glacier ice ends and sea ice begins. There does appear to be a narrow strip of sea ice between the two piedmonts. The general aspect of the coast-line is shown on Fig. 8; Evans Coves are immediately to the right. In line with Mount Melbourne is a very deep inlet, which is shown from a slightly different point of view. On Fig. 8 this is termed the Campbell Glacier. Farther to the west is another deep inlet (called by the Scott Expedition “Corner Glacier”). West again of this lies another deep inlet (called by them Priestley Glacier), apparently occupied by a large glacier. Farther still to the left is Mount Baxter, apparently of the order of about 8000 feet in height ; and then to the left of this rises the majestic table-topped mountain, Mount Nansen, 8000 feet high according to Mawson’s survey, 8788 feet according to the Discovery observations. This is capped with Beacon Sandstone, with apparently limestone below the above formation, the whole resting on a massive foundation of gneissic granite. Farther to the left is the wide, deep valley of the Reeves Glacier, with Teall Nunatak to the right front and Hansen Nunatak near the centre. The massifs of Mounts Larsen, Gerlache, and Crummer, also mostly of granite and entirely formed of crystalline rock, separate the Reeves from the Larsen Glacier on the left. Next the massifs of Mounts Bellinghausen, Gerlache, and Priestley separate the Larsen Glacier from the David Glacier. Time did not permit of an examination of the Campbell Glacier in 1908-9. It seemed formed of very gently-sloping glacier ice for a great distance inland. Corner Glacier probably contributes ice to the Nansen Piedmont, as does the Priestley Glacier. The description of the ice formations between Terra Nova Bay and Geikie Inlet may commence with the Drygalski Barrier, and thence we will proceed inland up the glaciers. The Drygalski Ice Tongue is about 38 miles in length from the shore to its seaward end. At 10 miles west of its extreme point it is 7 miles in width, at 20 miles west it is 13 miles in width, and along the shore about 25 miles, Its general appearance, as seen from Cape Ivizar, is shown on the following sketch. * Lieutenant Campbell’s party of Scott’s recent Antarctic Expedition discovered and explored several new glaciers contributing to this piedmont. They will shortly be described by Priestley. ‘paze12e)6 A)iaeay uaaq Sey 'aquesb a1ssiat6-qns yo paw.04 wang $7 “queqsip Sajlw aasy] Buaqmous abueq ‘801 BAS YIM PaJdA0) JOJU] BIMI9H ‘JaA9| CaS aroge 32a) 009 ABZIAY adey ‘anbuoy sa1iseg 29) 1415/2640 ° JO ulead MOUS jaAa7 = e é - oWUI asay seau sassed Kijenpes6 . i t ’ 7 Pie i Be a al nih ee © ays | datoey9 piaeg | \ l ‘auINOgiaWaW Aiqeqaid ‘uasuenaw Agequd =| i 1 8 sq erg Jo 118M ‘ b Jaiueg 143/e6Kug Jo adh yai7e)/6 andy uleqUNOW qUeISIP Aa, ulequnow yweIsIg |; 4a1d2]9 Uassey } 7n9-49/28/6 726 e 1 AIAALYG IYAClD ‘JISSeW JowwNID i HeM alltAsa.g f ‘Passerasd YyInW pue swseY) ul Bulpunoge Ayoowwny s) adeyuns ayy Pue aysejia)'uasiay ‘yissew Aajisaild 1 anbuoy dAaiueg aay = sjebAug ‘uasneybuijjag 4ahewnan spjouxay ade) 50 GLACIOLOGY This sketch shows in the foreground on the left Cape Ivizar, which at the point where the sketch was made is 600 feet above sea-level. The granite surface of this cape is strewn with erratics of intensely glaciated smail pebbles of diabase, gabbros, hornblende-lamprophyres, sphene-granites and pink felsites, &c. The rock sur- face not only exhibits numerous roches mountonnées, but is powerfully grooved in a general W.N.W. and E.S.E. direction. This is a point of special interest, as a glance at the map will show at once that this is the trend of the David Glacier, the principal feeder of the Drygalski Ice Barrier. It is obvious that this intense glaciation of the summit of Irizar is due to an ancestor of the above glacier, at a time when it was confluent with the Davis Glacier. There must have been a con- siderable thickness of ice over the top of Cape Irizar to have produced this intense glaciation. At this time the David Glacier before reaching the coast must have been at least 20 miles in width instead of from 6 to 7 miles as at present. The contour of the hills grouped around Mount Neumayer is clearly indicative that they have been heavily glaciated close up to, if not right over, their summits. If this inference is correct—and there seems little reason to doubt it—the David Glacier at its present outlet near Cape Philippi * was formerly at least 2000 feet higher than at present. On the north side of Geikie Inlet, and on the north side of the Drygalski Glacier, is a magnificent glacier-cut cliff, approximately 8 to 10 miles in length and some 1000 feet or so in height. It ends eastwards in Cape Philippi. At the back of this magnificent wall is the Mount Neumayer, Bellinghausen, and Priestley Massif. To the right, on the far side of the Drygalski Ice Barrier, rises the massif of Larsen and Gerlache, with the Larsen Glacier between. Dimly seen through the clouds on the day the sketch was made, behind Larsen is Mount Nansen, 70 miles distant, and still farther to the right is probably Mount Melbourne, 90 miles distant. It will be noticed that the surface of the Drygalski Ice Barrier is bristling with hummocks, ridges, and occasional seracs. On approaching the glacier from the south side we found that the sea ice by degrees developed a more and more undulating surface. We heard the roar of a crack opening in the ice near by, and as it was at the time a calm day, this cracking was probably due to the pressure of the ice of the active Drygalski Barrier.t There were here two sets of sastrugi, one directed N. and S., the true blizzard sastrugi, the other directed about E. 35° S. and W. 35° N., produced by wind coming from that direction from off the plateau. The latter sastrugi are made by the land breezes or plateau wind, the great “consequent” air stream which blows from off the cold plateau at night on to the relatively warmer surface of Ross Sea. This * Named after the distinguished geologist, the late Dr. Philippi, the associate of Drygalski on the Gauss-Antarctic Expedition. t Some of these cracks, newly opened in the sea ice by the forward pressure of the Drygalski Glacier Ice, were about 10 feet in width. THE DRYGALSKI GLACIER 51 wind started, at the end of November, between 8.30 p.m. and midnight, and blew at the rate of about 12 to 15 miles an hour until sometimes as late as about 9.30 A.M. the following morning, though usually it dropped earlier. Evidently in winter this plateau wind blows with intense violence, ripping out the old hard snow into deep chasms. The effect of the twofold directions of these strong winds added to the undu- lations caused by the pressure which impels ons the ice forwards, and Sy : B% probably the etching ge 5 3 effect of the sun on the 3S ° 5 Se ice and snow, combine to S§ Ve, make the surface of the me Drygalski Barrier in summer very difficult for sledging. As we ad- vanced, the undulating old sea ice raised rounded CROSS SECTION OF ONE OF THE ABOVE SNOW DUNES. CT es SE ridges to bar our pro- —* gress. The crests of the | s.orS.xe.eizzard a WNW. Plateau Wind waves rose first toheights >— > = Snow Cornice of 8 to 10 feet above their troughs; then to 40" feet 20 feet; gradually, with- out any visible trace of a tidal crack, the sea ice ween =~. Pe rose to the blue or pale Glacier Ice with recent crevasses (black).and c * old crevasses now filled with sapphire-blue ice(white). green ice of the glacier. Snow lids oF recent crevasses (dotted) The glacier surface here Fic. 9 resembled thatofastorm- tossed sea suddenly frozen. Long embankments of hard snow trending about E. 30° 8S. and W. 30° N., parallel to the plateau wind, joined billow to billow. The north-easterly faces of these embankments were precipitous and often overhung with a snow cornice, producing a seemingly endless series of more or less impassable ravines. On following the embankment for a few hundred yards it would be found that the bottom of the chasm shallowed, and it was found possible to lower the sledge and get across it. The structure is illustrated diagrammatically in Fig. 9. The extraordinary structure produced in the surface of this glacier as a result of a combination of pressure ridges, blizzard sastrugi, and plateau wind sastrugi, is shown on Plate XI. It presented a perfect labyrinth of high broken ridges, with 52 GLACIOLOGY gentle to steep slopes directed southwards, and vertical to overhanging cliffs with snow cornices directed northwards. These chasms were usually about 40 feet deep. According to aneroid levels, which cannot be considered very reliable, as the crossing of the Drygalski lasted for six days, the high portions of the Drygalski Barrier on the route where the northern party crossed it ranged from 130 feet to about a maximum of 200 feet above sea-level. At about a couple of miles south of its northern margin the Drygalski Glacier merged gradually into an undulating snow plain about 100 feet above sea-level. Where this terminates at Relief Inlet soundings were obtained by Davis, first officer on the Mimrod, in 624 fathoms. The bottom was a fine marine mud. If the density of the Drygalski Ice be taken as ‘88, and the maximum height as 200 feet, the maximum thickness of the Barrier ice, on the line of section, would be about 1960 feet. Obviously, therefore, at Relief Inlet, where the thickness of the Barrier is only about 800 to 900 feet, the Barrier must be afloat; and even where the Barrier on our route of crossing was thickest, if the depth of sea water is still maintained southwards from Relief Inlet at over 3700 feet, the Barrier must be afloat there also. But the question is, Is the depth found at Relief Inlet maintained right under the Drygalski Barrier? As yet no soundings have been obtained in Geikie Inlet. Two miles E.S.E. of the end of the Barrier Captain R. F. Scott, in the Discovery, got a sounding of 300 fathoms, and at a spot 3 miles to the south-east of the Barrier end one of 368 fathoms. If this shallower depth of 1800 feet be maintained under the highest point of the Barrier on our route, viz. 200 feet, the ice there having a total thickness of 1960 feet, the ice there below sea-level would be about 1760 feet thick, so that it would just float in the 1800 feet of water. It therefore becomes a nice point as to whether the Drygalski Ice Barrier is for the greater part aground or afloat. Probably the centre is aground, the sides afloat. As already stated, no definite traces of a tidal crack were observed by us on the south side of the Drygalski, at the point where we first struck it, but at the pot where we made our second (the successful) attempt to cross it there was a curious section of this kind (Fig. 10). At Relief Inlet the crevasse into which Mawson fell probably marked one of many tidal cracks. The whole of the glacier is a perfect network of crevasses, and, on the assumption that many of them extend right down into sea water below the bottom of the Barrier, the Barrier must be capable of differential movements, so that it may be likened to a slab of flexible sandstone (itacolumite). The eastern extremity of the Barrier was determined by Scott to be 70 feet high. At a distance of 2 miles off it the water is 1800 feet deep, so that if this depth is maintained under the eastern end of the Barrier it must be afloat. The curious growths of moss ice which were so conspicuous above the lids of the crevasses near our position, marked on map of Drygalski Ice Barrier 1.12.08, imply probably, as already suggested, that the crevasses for about 2 miles north of the junatak lacier - by the ice in the in the foreground PLATE XI LOOKING NNW M* Nansen 6000 FF [Between pp. 52 and 53 PLATE XI LOOKING WEST LOOKING NNW M‘ Howard ce) Les Mt Neumayer mt Bellinghausen Mt Gerlache betel Hansen Nunatak Me Nansen ; David Glacier on rok ide pf (ne Drygalshi rt : Larsen Glacier a Ff Reeves Glacier = behind Deygalsh Barrier Giscer cerry ' : : : ' OE ee orcgroared : Rugged Hille DRYGALSKI ICE BARRIER TONGUE [Between pp. 52 and 58 THE DRYGALSKI ICE TONGUE 53 southern margin of the Barrier at this point are filled with sea water. The con- vexly-shaped lids of the crevasses, met with on its northern side at about 2 miles back from the margin, suggest also that the fact of their being in relief is Glacier Ice f ' ' ) I S Possible tidal crack 100 Eo. 120 €¢! we Sea water t a ‘Bank oF 4 hard snow Surface of sea ice Ses levely\ * pee Crevasse Crevasse Crevasse (Base of Glacier not shown) Fie. 10 due to sea water fillmg the crevasses at a depth, and constantly giving off vapour, which is built up in the form of arched girders across the tops of the crevasses. No trace of moss ice, nor of arched crevasse lids, was observed by us in the central part of the Drygalski Barrier. Diagrammatically the section appears to have been as follows :— _ Moss ice over Arched lids over NWUSTORGEVASSCS ae 8 UES = > Che crevasses In this area the crevasses have : <5 — flat lids,mostly countersunk. 57+ > Relief Inlet sea _/eve/ SOUTH Marine mud bottomy TRUE SCALE Fic. 11 It is, therefore, highly probable that there is actually sea water under the Drygalski Barrier on our line of march for 2 miles inwards from either margin. As far as the evidence of the structure of the lids of the crevasses go there is no evidence that there is sea water under the central 10 miles of the Drygalski Ice H 54 GLACIOLOGY Barrier, but this in itself is not evidence that the Barrier is aground. If we examine the evidence further on the north side of the Barrier as to whether or not there is a tidal crack the evidence is unsatisfactory, for all the sea ice had gone out at the time of our visit, and the Barrier ice was, as already stated, traversed by a network of cracks and crevasses, and was intersected with what we called ice barrancas and ice dongas. The origin of Relief Inlet (see Plate [X.), as well as of some of the ice barrancas and dongas, is almost certainly to be sought in shearing, the result of the forward movement of the Drygalski Barrier. Relief Inlet has the form of a long, wide curving natural dock in the Barrier. Its general appearance is shown in Plate XII. Fig. 1. The sea under the glacier near here is over 600 fathoms deep. The glacier is, therefore, there, probably a piedmont afloat. In February 1909 there was open water at the bottom of the inlet for about 2 miles up from its mouth ; for the remaining 4 miles of the inlet, examined by us, it was floored across with sea ice, very much cracked, with sea water showing through the cracks and numerous seals lying on the ice. Its general appearance at the spot where we made our unsuccessful attempt to cross it on the return journey from the Magnetic Pole area is seen in Plate XII. Fig. 2. This ice barranca, a continuation shorewards of Relief Inlet, is about 150 yards wide and 50 feet deep. It will be noticed that it curves to the left to- wards Cape Philippi, which is the northern boundary of the Drygalski Barrier on the coast. At the point where we attempted to scale the cliff it was for its upper part wholly formed of snow, that is, for fully 20 feet. Perfect curtains formed of icicles concealed the middle part of the cliff from view, and its base was hidden by drift snow. It is difficult, therefore, to say whether this old snow was resting on old sea ice or on glacier ice. Relief Inlet, and the ice barranca in which it terminates inland, represent one of many shear planes which mark off the Drygalski Piedmont from the Nansen Piedmont. In travelling from a point a short distance to the north of this barranca, on our outgoing journey to the Magnetic Pole Plateau, we passed a number of what we called ‘‘ice dongas.” These had the appearance of small trough faults and step faults. Their appearance is shown in the following diagram (Fig. 12). For some time before reaching the first ice donga Mawson and Mackay reported that sea water could be seen at the bottom of some of the cracks in the undulating surface of ice and snow over which we were sledging. The dongas, like the larger barrancas, are probably formed by shearing movements. Occasionally, but rarely, we passed by an ice knob some 10 feet above the general level of the plain, and they reported that they could see ice to a depth of 30 to 40 feet in the sides of a crevasse running through one of these knobs. After crossing this ice donga we traversed four pressure ridges, each of them with a small downthrow of 10 PLATE XII H Fie. 1. RELIEF INLET Fic. 2. RELIEF INLET A shear plane 200-300 yards wide in the Drygalski A great shear plane in the Drygalski Piedmont Ice Barrier, looking 8.E. Fic. 3. POOL OF SEA WATER Near pressure ridge of the Larsen-Drygalski Piedmont Pe : 4? a + SS adie Sore ee eS ‘ Fic. 4. ENGLACIAL MORAINE Fic. 5. LOOKING TOWARDS THE REEVES GLACIER In sea cliff of the Reeves Piedmont With the Hansen Nunatak showing just over the sledge [Zo face p. 54 THE DRYGALSKI ICE TONGUE 55 to 15 feet in the direction of the Reeves Glacier. We were, consequently, still in the region of pressure of the Drygalski Barrier. Farther to the north-east was a large moraine bank with blocks of granite up to 7 feet in diameter. This was a reddish porphyritic granite, with pink orthoclase crystals up to 2 inches in diameter. It was associated with sphene-diorites, aplites, and fine-grained dolerite. This large moraine must either have been resting on the sea bottom, or was partly embedded in the surface of some old glacier ice. Sedimentary rocks were not noticed in this moraine. Farther to the north-west, after passing over a little more ice that looked like glacier ice, we passed, at the bottom of a gentle undulation, cracks in the ice with open water in the cracks. We tasted this, and found it to be very salt. There can be no doubt that it was sea water. Beyond, to the north-west, glacier ice belonging to the ICE DONGA on DRYGALSKI BARRIER. Siow cornice formed by Aateau wind <—— ~ 80-6090. gy Sa Sace5 Reeves Glacierroseagainst L ; 7 > ee This crevasse widened tamineetestecolls trom D0) 9 8 Ie Feet in about |3hours ye C c . Traces of Foraminifera between 8 a.m. of Dec. 172 to 80 feet in height, and on the ice at the and Sp.m of the sameday sides of the cracks Fie. 12. ICE DONGA ON DRYGALSKI BARRIER This “ donga” is a shear plane or shear zone in the Drygalski Barrier, due to differential movement. The central parts of the donga are probably old sea ice traversed by a_ perfect labyrinth of crevasses. The line of demarca- tion between the Nansen Piedmont and the Dry- galski Piedmont may, therefore, be drawn provisionally at these cracks in the sea ice. In retreating from the all but impassable ice waves of the Reeves Glacier towards Backstairs Passage (see Plate IX.) we reached another extensive moraine. In addition to numerous large boulders of granite, we found here fragments of sandstone and limestone with small pieces of grey clay shale showing faint impression of rootlets (?). This was, no doubt, derived from the Beacon Sandstone. Each boulder was surrounded by a thin crust of ice, through which, when sledging, we continually broke, falling into the thaw-water below. Between this moraine and the rocky coast at Backstairs Passage, a distance of about 1 mile, was a stretch of what certainly appeared to be sea ice, with an occasional open pool like that shown in Plate XII. Fig. 3. At the back of the pool is a pressure ridge in the glacier ice or old sea ice. This pressure appeared to come from the Drygalski part of the Barrier. Still farther inland were marine muds, forming conical mounds resting on a foundation of ice. The muds were 20 to 30 feet above sea-level, and washed in among the boulders. This ice tasted slightly saline, but not as salt as typical sea ice. Probably it was old glacier ice; its salinity was due to its having been over-ridden 56 GLACIOLOGY by upthrust marine sediments. In one place on this same moraine we observed a very large and delicate compound siliceous sponge firmly attached by growth to a granite boulder. (See figure in Chapter on Raised Beaches.) These muds, which are probably of the nature of upthrust marine muds, are described in detail in the Chapter on Raised Beaches. The structure of the piedmont between the Drygalski-Larsen and the Reeves Glaciers has been described in detail, as it is of great import in the glaciology of this interesting region, and is the key to the mystery of the Ross Barrier, as will appear later.* When ascending Back- stairs Passage we observed two considerable moraines sweeping out from the shore Shear planes Drygalski Relief lee Danga Old neeves lee Barrier Inlet moraine Glacier ‘624 fathoms — —Ssea — -floor— — 37 miles. Enlarged Section of above Disjunctive planes Y A in part due to ease ; B Ice : |. : Old moraine Reeves Glacier Donga ‘on GEO, 1ce. Sea ice. ayer) seg level STSEs Fie. 13. SECTION ACROSS THE DRYGALSKI PIEDMONT, AFLOAT FOR A GREAT PART at the foot of the Reeves Glacier seawards. In travelling from the Drygalski Glacier around the ice cliff of Terra Nova Bay to Evans Coves, one of our col- leagues on the Nimrod took a photograph of the ice cliff with dirt bands embedded in it (Plate XII. Fig. 4). While much still remains in doubt, a section may be drawn provisionally from the farthest point of our route up the Reeves Glacier to the Drygalski Barrier at Relief Inlet, and thence to the point where we first reached the southern side of the Barrier (Fig. 13). * A summary of the Drygalski and Reeves Piedmont will be given when the rest of the evidence supplied by its feeding glaciers has been stated. THE REEVES GLACIER 57 Reeves Glacier. Viewed from the Drygalski-Reeves Piedmont, the Reeves Glacier is a magnificent spectacle, some slight idea of which may be gained from the photograph, Plate XII. Fig. 5. Mount Nansen is here seen from a distance of about 35 miles, and Mount Larsen from a distance of about 20 miles. Hansen Nunatak, near the centre of the glacier, rises to a height of about 2800 feet. It is a most impressive and majestic monolith. The most striking glacial feature in this landscape is the stupendous granite cliff of Mount Larsen, which towers some 3000 feet above the glacier ice at its base. There can be no doubt that during the maximum glaciation the ice of the Reeves Glacier pressed high up against the giant cliff of Mount Larsen, and must have almost, if not altogether, overtopped it. The general outline of its summit is very suggestive of its having been completely glaciated. The Reeves Glacier is an immense outlet glacier, about 12 miles in width, and about 25 miles in length measured up to the area on the west side of the great horst, where it merges gradually into the snow-field of the Magnetic Pole Plateau. Fig. 14 shows details of the Larsen-Gerlache-Crummer Massif, which separates the Reeves Glacier from the Larsen Glacier. The Reeves Glacier falls about 4000 feet in its 25 miles of length. Two moraines derived from it are conspicuous, the northern and larger one derived from near Teall Nunatak, and the other from neighbourhood of Hansen Nunatak. As already stated, these sweep out to sea across the Nansen Piedmont. The surface of this glacier undulates strongly, and is very heavily crevassed.* Backstairs Passage is a shallow and narrow breach in the rocky massif which divides the Reeves Glacier from the Larsen Glacier. It may be described as a small spillway and branch of the Larsen Glacier. It is about a quarter to a third of a mile in width, and about 2 miles in length. In this distance it ascends about 1500 feet. Though somewhat steep it is only slightly crevassed, and on the whole offers a good surface for sledging. The next glacier to the south is the Larsen. It is from 2 to 3 miles in width, and, like the Reeves Glacier, is about 25 miles in length. In this distance it falls over 3000 feet, its slope being very steep just before it reaches the coast. It descends there in a turmoil of great pressure ridges, heavily crevassed, to join the Drygalski Piedmont. North-westwards from its junction with Backstairs Passage right on to the plateau the Larsen Glacier is not very seriously crevassed, and affords a good road on to the plateau for sledging parties. The Larsen Glacier shows every evidence of having at one time overridden Mount Crummer, which now rises approximately 1500 feet above its surface. * When attempting to force a passage up it our sledge was on several occasions all but engulfed from the collapse of the snow lids, and dragging a sledge up the rolls of slippery ice is extremely laborious. The glacier might, nevertheless, be traversed by a party who could afford an abundance of time for the purpose. By far the best track so far found for any one desirous of mounting the plateau in this vicinity is Backstairs Passage. NUSNVN LTNOOW CNV YAIOVID NASUVI NAWMLAd ‘VAS ssou ‘ISVOO OLLOUVINV DNIMOHS HOLES FI Pla 4319249 | saaaay 390092 ‘yeqeuny 4000S (MN 6uryjoo})'uasse7 sw uasuey A , ‘ ‘ ' i 5 409X895 | yawefg sanzay (auUUNAD IW ! eee J do08 -/ 0092 44000S | -aBessey aneysyoeg 4319219 uas.se} “uasueN jW yeqeuny ussueH “UasseTW 2 aupeya9 aw ' i ' ' f | ' PLATE XII Fic. 1. BACKSTAIRS PASSAGE GLACIER Fie. 2. LOOKING §8.E. DOWN BACKSTATRS GLACIER With Mount Crummer to right Looking north to Mount Melbourne Fic. 4. MAGNETIC POLE PLATEAU About 80 miles inland, looking north towards the distant plateau ranges. On right the snowfield falls toward the Reeves Glacier | Photo D. Mawson Fic. 3. MAGNETIC POLE PLATEAU Mount Larsen to left, Mount Bellinghausen to right [Zo face p. 58 ISVA-HLNOS ONIMOOT SI MAIA LSHMOT HHL ‘UMIOVID ADVSSVd SUIVISMOVA DNIGNAOSV NAHM HLMON OYNIMOOT SHHOLAMS ‘ST “IY 49}92}9 4a19e19 uasiey abesseg sueysyoeg 4awwnd);W 4919219 }aqdwed © ausnogiawiW ausnogiaw3iW dea daag 60 GLACIOLOGY The outline of Mount Crummer, and the outlook from the Backstairs Glacier, in the direction of Mount Melbourne, are shown on the sketches on Plate XIII. The David Glacier. This glacier is another of the outlet or spillway type. At Cape Philippi it is about 8 miles in width. It also appears to be about 25 miles in length. Heavy ice-falls could be seen far inland up this glacier as viewed from the sea ice. Its surface is so rugged as to be almost impassable. It is evidently an important outlet for the snow-fields of the plateau. Its great pressure ridges, shearing planes, and numerous crevasses testify to its activity. Snow-fields and Ice-fields of the Magnetic Pole Plateau. Plate XIII. Fig. 3 shows the general appearance of the snow-fields at the back of Mounts Larsen and Gerlache. A study of this photograph makes it clear that the summits of Larsen and Nansen would be easily overridden by an ice sheet were the snow surface about 2000 feet higher than it is at present. The surface of the plateau was found to undulate in broad billows about 40 to 50 feet deep, and many hundreds of yards from crest to crest. A crevasse was observed as far inland as 55 miles from the coast, and ice-falls, formed above of hard marbled snow, were observed at a total distance of 70 miles inland. The whole snow-field must, therefore, be in a state of slow movement, at least as far inland as this. Strong undulations in the snow surface, still about 50 feet deep from trough to crest, continued inland for fully 90 miles back from the shore, and 70 miles back from the inner edge of the plateau horst. From this last distance of 90 miles inland the undulations lessen, and could not be recognised near the summit of the plateau. This attains an altitude of 7350 feet at a distance from the coast at the Reeves Glacier of 180 miles. No trace of any material approaching to ice could be seen on the inland side of the ice-falls, the latter being situated 70 miles inland. A sketch of the general outline of the ranges bounding the Reeves Glacier from Mount Nansen north-westwards through Mount Baxter and Mount Mackintosh is shown on Fig. 15 and on Fig. 4 of Plate XIII. The plateau character of the inland ranges is very obvious in the sketches; some of the rocks—particularly those of Mount Mackintosh—appeared to be very black, which suggests that they may be formed of basic material. They are largely formed of Beacon Sandstone. It will be noticed from the section on Plate XIV. that the summit of the Magnetic Pole Plateau is very flat, not varying in height by more than 50 feet over a distance of 30 to 40 miles. In a distance of 35 miles a fall of about 90 feet was recorded by us in a general direction towards the north-west from the summit of the plateau to the farthest point reached north-west. Our direction of march at the time was about N. 30° W., and it was in this direction that the slight fall was recorded. It does not, of course, follow that this was the direction of greatest fall. That we actually passed over the summit of the plateau before reach- SNOW OF INLAND ICE 61 ing our farthest point north-west, is proved, apart from the levels, which in themselves are slender evidence, by the remarkable and complete change in the direction of the prevalent winds. As indicated by the trend of the sastrugi they blow to the east of the summit towards Ross Sea, to the west of the summit towards Adélie Land.* Structure of Inland Snow. It is much to be regretted that, owing to lack of time and food, we were unable to sink a shaft, much as we wished to do go, in the inland snow-fields to discover their structure. The importance of this has been impressed by us upon the Australasian and British Expeditions in Antarctica in 1911-14, Sastrugi, 3 feet deep, failed to reveal anything more than tough snow. No distinct trace of granulation was noticed; in fact, no true névé seemed to form M'Mackintosh M'Baxter M* Nansen Basalt 8000 F ae = ee a, = Am By eee BS ee SS Fic. 16 in this surface portion, on account, doubtless, of the extreme cold and dryness of the plateau. The granulation process may be said to be at a minimum on the high plateau. SUMMARY AND PAST HISTORY The whole length of the Reeves and Larsen outlet glaciers with their snow-fields and piedmonts is approximately 200 miles, made up as follows :— Miles. Snow-field and underlying ice : : 3 , . 155 Outlet glacier . : : : : : : : 25 Piedmont : : : : : 5 : : 20 In the case of the Larsen Glacier its piedmont merges in that of the Drygalski Glacier, and so has the length of 38 miles, as compared with 20 in the case of the Nansen Piedmont. In the case of the David Glacier, only the length of its pied- mont, the Drygalski Ice Barrier, is known, and that is 38 miles. * This fall of the plateau to the north-west is now quite confirmed by the recent observations of R. Bage, S. Webb, and C. F. Hurley of Dr. Mawson’s Australasian Expedition. They found the plateau rose steadily from Adélie Land to 5900 feet, their farthest point reached, in lat. 70° 36’ S., long. 148° 12’ E I 62 GLACIOLOGY These large active glaciers are the outlets for the inland snow- and ice-fields. They are nourished by snows, which probably fall mostly in spring, autumn, and winter. These snows are borne inland at a high level, partly by the widespread Antarctic cyclone, the high level constant W.N.W. to N.W. wind, partly by a local intermittent N.E. wind coming off Ross Sea. The indraught of the latter is due partly to the physiographic relief of the plateau giving a comparatively steep down grade towards Ross Sea, partly to the difference in the specific heats of ice and sea water, which leads to a much greater daily range of temperature on the plateau than at sea-level, the daily range on the plateau being about 20° Fahr., while that at sea-level is only about 6° Fahr. This big range of temperature en- courages air currents. At night, in December—January (the time of our observa- tions), the rapid chilling of the plateau surface starts air currents—the plateau wind, of the nature of a land breeze. By about 9 a.m. the following morning the sun, if the day is fine, has so warmed the plateau that the land breeze, or fohn, is entirely checked, and the withdrawal by night of cold air masses off the plateau having established a high level down gradient from Ross Sea towards the plateau, snow- bearing air currents stream in over the plateau from above the open water of Ross Sea from the north-east. The Reeves Glacier fans out on reaching the sea coast to form the Nansen Piedmont, stretching seawards for 20 miles. This piedmont is joined by sea ice to the Drygalski Piedmont. The Larsen and David Glaciers together form the Drygalski Piedmont, which extends seawards for 38 miles from the coast. At its sides, especially its northern side, where there is a great accumulation of drift snow from the southerly blizzards, and for a distance of about 10 miles west of its seaward end, the Drygalski Barrier is afloat. The central part of the Drygalski Barrier is probably aground on its own bottom moraine or submarine esker. This ice mass is still in forward movement, perhaps a yard a day in December, as proved by the great shear planes which have produced Relief Inlet and the ice barrancas and dongas. Further proof of this movement is afforded by the upthrust marine muds, as described in our Chapter on Raised Beaches. The bottom moraine and fluviatile material of the Drygalski Barrier is probably of great thickness, perhaps of the order of 1500 to 1800 feet, as suggested by the only three soundings available. According to this view, the piedmont is riding on a species of railway embankment, which it has constructed as a support for itself when, as the result of its increasing buoyancy, as deglaciation succeeded the time of maximum glaciation, it tended to float up higher and higher above the rocky bed of the Terra Nova Bay.* That during the maximum glaciation it must have com- pletely filled even the deepest hollows alongside of it, such as the 668 fathom * That there are passages for ocean currents under the ice over the top of the embankment is rendered probable through the persistent pool of open water north of the Drygalksi Tongue. ‘. PLATE XIV SECTION ACROSS SOUTH VICTORIA LAND FROM MAGNETIC POLE REGION TO ROSS SEA. Winds blowing Northerly &Nor-Westerly Cowards Winds blowing ESE Adelie Land& south of == Parting of the winds —— to ENE ited Balleny Islands. and top of the Plateau. Bossier: MAGNETIC POLE “4 eo ee REGION. M‘ Mackintosh ; MENansen 8000 ft. 7260 7350 7320 7040 7000 68/4 BeaconSandstone with\possibly some limestone at its base. *. Surface of hard marbled snq Broad shallow uridulations. = Reeves Glacier branches off descending between M“ Larseng Nansen ‘ Larsen Track of Northern Party Depot. crossing the Drygalski BaFrier. iM‘ Larsen 5000 ft. M‘ Gerlache o| M*€rummer ; At the depot of Relief Inlet on North side of Glacier sea 624 fathoms deep. ea ROSS SEA Possible Ceore palsions = as suggested by fragments E 1° Of, sorustone in the lavas .->.- of Erebus. Fault zone with heavy SE x 4079 y SF Fault zone with ches | downthrows to the West. THE downthrows to the East. THE oo 2222 22 2e one 22 -- +«-------GREAT HORST.------------+<----SUNKEN PLATEAU--> , ° 20000 40000 60000 B0000 Metres. ° 1000 2000 3000 Metres Longitudinal Scale. T = ab Stavute Miles. Vertical Scale. Se == 5 Feet. TRUE SCALE. Cape Irizar meomner wed ne (alrimim) sot combined Drsgaiehl ond sheeves Glaciers) iy .. o 5 ee Summit strewn Seaward end of -with Erratics...¢5 0 gnyt Present Drygalski Barrier Reeves Glacier Barrier. ORC EIKIE INLET Sounding 300 fathoms RELIEF INLET Moraine Moraine Probably Granite Sea Level. Oid'* snow on ice: Semmeaair teat *|_Sea Level SOUTH |: <2 ee NORTH vs _ 624° fathoms ne ~! 2S 12900 16 = Metres SI miles. : eal acral Vertical Scale 6 ry 10 Statute Muss 1000 3 S000 Feet RUE SCALE Shs LONGITUDINAL AND TRANSVERSE SECTIONS ACROSS THE DRYGALSKI ICE BARRIER TONGUE. : : Shackletons soundings Scotts | N D Ee xX Drygalski Barrier on North edge. 9 Soundings. Shore 624 Fathoms.6 8B E. Chiefly Sub-gneissic granite (with biatile and allanite) traversed by veins of pegmatile. The granite intrudes dioretic rocks including Sphene diorite, and is itselF intruded by dykes of lamprophyre. 300 fathoms= _ 368 fathoms The Beacon Sandstone (Gondwana ?) with appearance of lintestone near its base, Possibly the limestone may be Cambrian. ENA e lANCeN As wad TRUE eA. Probable glacial beds and marine Old Drygalski Barrier RELIEF INLET ; ey Crevassed glacier ice Old snow., Old snow ae muds below pugateh Barrier and LS fear ace sed g bi eee Reeves Glacier Barrier. —— ST a ea GEIKIE INLET ROSS SEA Snow. névé, ice fields. and glacier ice. SOUTH NORTH with some ice formed from snowfall on old sea ice, and sea Ice. ss 5580808 SSS =>, TRUE SCALE. H.E.C Robinson, Delt. Sydney.NSW. Sea Level Sea level. [Between pp. 62 and 63 ~4r Tieet 220894. Wiel MOA x “ae ree er. : ye Aram. | Wye Seni soireia fides anes b, pinnae ‘3 t esnaeh tdebege . toa uA yeni vs ibs > ——e Tw oy 7 A Ald: G4. ate Tait "SAT ; * ay wna! trakeen TT PIT { x ” * THE DRYGALSKI-REEVES PIEDMONT 63 sounding at Relief Inlet, is abundantly proved by the positive evidence of the former height of the ice flood during the maximum glaciation. The most conser- vative estimate of the heights up to which the adjacent mountains have been glaciated places the former thickness of the ice here as at least 1000 feet, almost certainly 1500 feet, and in the case of the Reeves Glacier probably 3000 feet higher than it is at present. Therefore at Relief Inlet during the maximum glaciation the ice would have been 668 fathoms + 1000 feet =in round numbers 5000 feet thick. Thus we have evidence of three kinds as to the extent of former glaciation :— 1. The height to which the rocks above sea-level are glaciated above the level of the adjacent glaciers. 2. The depth to which the rocks below sea-level have been scooped out by the old glaciers when they pressed hard on their rocky bed, as at Relief Inlet. The sounding of 624 fathoms at Relief Inlet does not probably represent the full former thickness of the Drygalski ice below sea-level, as the driving tube on each of the three soundings made at this point always brought up with it fine marine mud. It may be noted that about 2 miles farther east we obtained a sounding of 668 fathoms. 3. The height to which the Drygalski Barrier has aggraded its own bottom moraine and submarine eskers as it gradually floated up higher and higher as the deglaciation progressed. That the Drygalski Barrier is an outlier of the former Great Ice Barrier, which during the maximum glaciation was continuous with the Drygalski-Nansen Piedmont, will become clear when the glacial evidence along the coast between the Drygalski Barrier and the Ferrar Glacier is being discussed. It is much to be hoped that many more soundings will be secured along the coast and in various parts of Ross Sea by the present British Antarctic Expedition. It would be of great interest to further develop by sounding the contour of the sea floor eastwards of the present termination of the Drygalski Barrier. It would obviously also be of importance to secure soundings in Geikie Inlet. Much light will be thrown on the structure of the Ross Barrier by a further study of the Drygalski-Reeves Barrier. Its structure, compounded, as it is, of a number of ice jetties united by strips of old bay ice reinforced with the granulated snowfall of many years, makes the Drygalski-Reeves Piedmont in many ways a key for the interpretation of much that is at present puzzling in the structure of the Ross Barrier. Lastly, it may be added that the observer cannot but be impressed with the stupendous erosive power of the glaciers of this region during maximum glaciation. The D’'Urville Wall and northern cliff face of Mount Larsen are eloquent tributes to the facetting power of glacier ice. CHAPTER IV GLACIOLOGY (continued) CAPE IRIZAR TO DRY VALLEY From Cape Irizar southwards to the Ferrar Glacier, a distance of over 150 miles, the coast belongs to a somewhat sunken region on the line of the Antarctic Horst. While Mount Nansen on the north rises to over 8000 feet above sea and the Royal Society Range on the south to nearly 13,000 feet above the sea, there are only a few of the coastal mountains within the area now being considered which exceed 5000 feet in altitude.* One exception to this rule is Mount Davidson, the height of which is given by Scott as 8127 feet. The plateau character of the rocks is obvious. An old peneplain of crystalline rocks is capped with Beacon Sandstone throughout the greater part of this coastal section. The sandstone itself is mostly capped by sheets of black rock, probably sills of diabase. It is possible that some of them may represent contemporaneous lavas. The horst in this region is breached by transverse valleys having a general east and west trend. Taken in order from north to south, these are :— 1. The Davis Glacier, with the Clarke Barrier to the north and the Cheetham Ice Tongue to the south. 2. The Harbord Ice Tongue. . The Nordenskjéld Ice Tongue, and Mawson Glacier with the Cotton Glacier. . The Fry Glacier. . The Penck Glacier. . The Mackay Glacier, with the Geikie Glacier. Cape Irizar, a bold headland of pink granite with hornblende, biotite, and allanite, traversed by dykes of lamprophyre, forms possibly part of a long island, Lamplugh Island, trending north by east and south by west. To the south it is bounded by the Cheetham Ice Tongue. On the north it is bounded by Geikie Inlet, and on the west by the Clarke Barrier. The island, if it be an island, ao —& Ww * Viewed from the top of Mount Erebus by Priestley and a sledge party of the Scott Expedition of 1910-13, mountains seen far inland at the back of Granite Harbour, &e., appeared to rise to heights of over 8000 feet. + The uncertainty is due to the fact that inland it dips sharply under the low-lying ice sheets of the Clarke Glacier and Davis Glacier, and it is just possible that it may prove eventually to be a peninsula, but it is probably an island, 64 CAPE IRIZAR 65 is about 10 miles in length by about 2 miles in width. The general appearance of Cape Irizar and the coast in its neighbourhood is shown on the sketch below (Fig. 17). The observer is looking about W.S.W. up the Clarke Glacier, with Mount Howard in the distance. Cape Irizar Mt Howard Cape Reynolds Our lookout point : Clarke Glacier Rocky point covered with patches of snow glacier ice. Glaciated roches moutonnees See BF a ? — xe oe Somer = & Se =e ye ae ST ean a a2 == ESE IG Cue A pe let Enea aa ee Ae Seles Sree =. > Crack in Sea ice with slabs of 5ea ice Forced up by pressure. - —- 5 ——— ni | maa : — = Fie. 17. View of coast looking to W.S.W. at point 8 miles south of Drygalski Ice Barrier Tongue The next sketch (Fig. 18) shows Cape Ivizar itself, about 600 feet high, formed of biotite allanite granite peeping out in places from under the ice calotte. The Basic Dykes cutting porphyritic granite = ——~, a SARA tse 2s Po UT e a 4 10 3 Red Porphyritic Granite. Fic. 18. DETAILS OF CAPE IRIZAR AND ITS ICE CALOTTE The section below is taken across the basic dykes shown in the upper sketch granite is intersected by an interesting group of kersantite dykes, described by Dr. Mawson in his chapter relating to the petrology of this area. On either side of the dykes, for a distance of a few feet, the felspars of the granite were deeply reddened as the result of contact metamorphism. This granite was also traversed by acid dykes, apparently aplitic in character, and of earlier origin than the basic dykes. These acid dykes are lenticular in character. 66 GLACIOLOGY The granite is traversed by small veins of a dark mineral which is probably biotite or schorl. The granite showed evidence of having been very heavily glaciated, showing that recently there was a great thickness of ice over its summit. On the summit were numerous erratics of gabbro, dolerite, hornblendic dyke rocks, sphene-granite, pinkish-grey felsites, &c. Between the Drygalski Ice Barrier and Cape Irizar we encountered several formidable cracks in the sea ice, evidently caused by the forward thrust of the Tongue. On November 28, 1908, we heard one of these cracks open with the peculiar noise of ice when being riven. It will be seen from this sketch that Prior Island is isolated from the mainland rocks on the left by a low stretch of piedmont glacier ice, which appears to be confluent with the Davis Glacier. Its height as estimated is only very approximate. Its strongly glaciated outlines are proof of a considerable thickness of ice having at one time over-ridden it. The sketch shows that the ice at its base, to the right, is now only 20 feet or so above sea-level. On the next sketch, taken 2 miles Prior Island : Granite. partly hidden Glacier Ice. Glacier /ce ' ey, overlying Granite. Ee rormer iminium; levelies Glacier ee ee i aaa under snow and ice. farther south, it will be seen that the north-east end of Prior Island is somewhat rugged and unsmoothed, so that evidently this was the lee side during maximum glaciation. The nature of the main coast-line immediately to the 8.S.W. of Prior Island is Shown on the lower sketch of Fig. 20. The gneissic granite on this part of the mainland was here very heavily glaciated in a general north-east direction, and the exposed surfaces were remark- ably fresh. As weathering, due to the great diurnal changes of temperature, is very rapid in these regions, the exposure of these rock surfaces through deglaciation must have been very recent. The direction of the strie pointing towards the end of the Drygalski Ice Barrier Tongue is interesting. The strive on top of Cape Irizar trend towards E.S.E., and were evidently formed by an ancestor of the David Glacier; while those near Prior Island trend towards the north-east, and were no doubt produced by an ancestor of the Davis Glacier. It is clear that the whole of the island, of which Cape Inizar is the northern end, has been formerly over-ridden by an ice sheet, the COAST BETWEEN CAPE IRIZAR AND THE NORDENSKJOLD ICE TONGUE 67 top of which, at a minimum estimate, cannot have been less than 1000 feet above sea-level, where the surface of the piedmont glacier is now only from 20 to about 50 feet above sea-level. Rock shown DavisGlacier Prior Island P ME BORO yer a ; Jateau paces oF a Ceonde Murray : fone [promo 5 Section : Piedmont Glacierice SECTION AT + (above sketch) Height about 150 Feet above Sea level Thin Glacier Ice. Thin Glacier ice 40 feet above sea level Very freshly glaciated roches moutonnees eS NS sown a A few Fine pebbles up to 2 inches i De ee NON SS indiameter rest on roches aes ; Sas moutonnees Tide crack Tide crack — ; NS tae als \ ENG eRe Se aS NEN A Sons : ‘ > SS ~ Grey IGReresic granite, porphyritic by white felspar. and traversed by veins of "coarse pegmatite (2) as weil as by darker and Finer grained granitic veins (). The granite 1s 8 perfect network of such veins Sea lice Sea water Direction of striation on the roches moutonnées A little bright green mass grows in the sand is towards the NE. and gravel in cracks in the granite. Fic. 20 The next outline sketch of the coast was taken at 164 miles south of the Drygalski Ice Barrier Tongue, and just north of the Cheetham Ice Tongue, looking westerly. Rack platform .. Piedmont ° ' (ce Barrier t High mountain. Mt Howard | S ‘ ‘ ; "3 GER - = a ~~. ete a 3 ——— =e MO SE= ae oe a Se ee Wg Sr ey : er at ==. — - Sea lee —~- Fic. 21. West coast of Ross Sea, 16} miles south of Drygalski Ice Barrier Tongue, looking westerly It shows an extensive coastal piedmont aground, with the plateau rocks in the background. Mount Howard has a very dark appearance, suggestive of dolerite or other basic rock. 68 GLACIOLOGY The next object of interest southwards is the Cheetham Ice Tongue, 17 miles south of the southern side of the Drygalski Ice Barrier. This small Tongue was about 40 feet in height, and seemed largely formed of snow. At the time it appeared doubtful whether it was a true ice tongue or merely a grounded or frozen in snow-berg. Mawson has shown it on his map as a tongue, and this view has been provisionally adopted. Mawson shows it as being attached to the Davis Glacier. At 19 miles south of the Drygalski Barrier is the Davis Glacier proper. It is very heavily crevassed. Its general appearance at its seaward termination, seen at a distance of about 3 miles, is shown on the next sketch. Davis Glacier Prior Island heavily crevassed. Granite. ‘ Se SS 5 : ° : 25 ee ei Rock of Gneissic Granite Rock = —- (See Following sketch). Judged from the height of the rock at the left of the sketch, the terminal end of the Davis Glacier may range from 300 to 500 feet above sea-level, possibly more. It is improbable that the Section al + height of any point along the coast from the Davis Glacier to Cape Irizar, following the coastal pied- mont, exceeds 1000 feet Gneissic Granite in altitude. Below is a ae ae with lighter pegmatitic bands (a2) section of the piedmont PG ee ice resting on a rocky ees point of gneissic grey ; ye Or ES ee Sea ice granite with veins of ais oo pegmatite. It will be ea as seen from this that the Fic. 23 piedmont glacier ice at the cliff face here is only from 70 to 80 feet thick, and at the top of the cliff about 180 feet above sea- level. The ice at the back rises to a considerably greater height, but probably does not much, if at all, exceed 600 feet, the ascertained height of Cape Irizar. Crevassed Glacier Ice COAST BETWEEN CAPE IRIZAR AND THE NORDENSKJOLD TONGUE 69 Fig. 24 is a continuation of the preceding section, showing the coastal piedmont aground for a farther distance of about 10 to 12 miles southwards. Mount George Murray is about 20 miles distant, and 17 miles back from the coast-line. The width of the coastal plain, on which the piedmont rests, is here about 15 miles. (See Fig. 26.) The Harbord Ice Tongue is about 30 feet in height at its eastern end, about 1 mile wide, and 5 miles long. It will be noticed that there is a very wide breach M! Smith M' George Murray Piedmont Glacier lee. 4500 Feet. 3600 feet. in the plateau between Mount George Murray and Mount Howard, through which gap the ice from the inland plateau passes seawards. The total aggregate length of coast seen in these two sketches is about 28 miles. The coastal piedmont is about 15 miles wide. The outlines of the hills to the left of Mount Smith suggest that they have been intensely glaciated right over their summits. The next sketch of the part of the coast which follows immediately to the south shows its configuration near the Mawson Glacier. In the foreground, just back from the coast, is the glacier ice of the piedmont. This gradually passes on to an intensely glaciated rock terrace, ME Smith M! Gauss? Mawson Glacier one porre Day Mr ey fosps MrChetwynd? WT Ks the alt glocter Flan ' old Glacial Terrace H * Oi Glacial Floor Destaet |!) /Dsteer Lena Oreanal Floor of Pormer outlet glacier 4 mountain | black mauntamn. ‘Stil partly covered by ice Fe eee —— . =e y ~~ eo oe 4 a AN pe mr a t Sea ice ay : = = - ~~ Piedmont Glocter ioe tena ? = ye — Shore endof - Charcot Bay — C.Bruce = - = =e == Nordenskjold Ice Barrier __~— —— ___ shold ce Barer seen at the centre of the sketch. This terrace is much overspread with large patches of morainic material (Fig. 25). The sharp peak at the back of this terrace is Mount Murray; it is evidently formed of a granitic rock, and its outlines showed evidence of its having been glaciated over its summit. It is of the nature of a tind. The wide gap between Mount Smith and Mount Gauss, at the bottom of which lies the Mawson Glacier, shows clear evidence of former much more extensive glaciation. The shore end of Nordenskjéld Ice Tongue is shown just to the left of Chareot Bay. This part of the coast appearing to be of special interest, several sketches were made of it. K ¥ 2 R = a2/ eas * ; ' § ; a S p "paz e126 hbuos79 v2ag aaey koy7 ‘ é 97709 40 OUEDION ‘ ! Sry a bose 2847 sqsabbns sulezunow 40 auij7nO “20/ Ja12€/9 JUOWPald auozspueg uoseag Ajquapiaz : a YS IW ssoy ay} 4O SyI0y syooy neareid ssne9.W ‘JOWO/D ps0gseH anBuoy samseg 99, psoquey 247 JO PUI'M'S 72 pee bees Cie BIQYS UO YIOL FIUOIN J ~~ i lig SS/UD JO aPIUPID —— ae ~ z = = a= eae niet) -=— (te re = ' a7jeas | ‘ a = rae é ———_ a SSR WEI Gy Ree ‘ ¥ ‘ * ' i i ; : S 2/ 42128/9 surequnow \ awog Wwe7sig ‘yI04 21829 g PI qwowpa/ 2U87S/0 ¥20/9 Jo Mo}J 40 1/15 ko padded “Sis wsep y7IM apueJs6 Ayary Ajjuasedde iS ne 1 : (2u079puesuo0reag) 490s Paly!JEI7S 3933 OO9IL s g p4emoy a uaMog3W Aeaany ab10an yunow $ > Ss THE NORDENSKJOLD ICE TONGUE 71 Fig. 26 is a panorama taking in about 20 miles of coast from the Harbord Ice Barrier Tongue to Mount Gauss. The view is taken from the flat top of the Nordenskjéld Ice Tongue, looking north-west towards Mount George Murray, and west by south towards the Mawson Glacier. The point of attachment of the Nordenskjéld Ice Tongue to the Mawson Glacier can be seen just at the point where that glacier comes down to sea-level. This attachment is much constricted by a long narrow gulf on the southern side of the Tongue, and by Charcot Bay on the north. The erosive force of the sea, impelled by the fierce southerly blizzards, threatens soon to betrunk the piedmont, and separate it entirely from its parent glacier. There is a great contrast between the appearance of this glacier on this southern side as compared with that of its northern. The photograph shows the features of the northern edge of the Tongue. Northwards this Tongue terminates in a precipice from about 50 to 70 feet in height. At the point where we crossed it, we discovered a very steep snow slope, shown in the photograph, down which we lowered the sledges. At the top of the cliff was a species of crevasse, separating the slope of hardened snow from the barrier edge. This crack was apparently due to a settlement of the snow drift, and in this settlement the snow cornice at the top of the cliff had been cracked across, thus :— Gag Broken snow cornice ae nN z 3 N Oritt snow resting against CHEF face \\ of Barrier and supported by the sea ice. Snowon Sea ice, the latter about 6 feet thick. Fic. 27. Section across northern edge of the Nordenskjéld Ice Barrier Tongue This aspect of the Tongue is in strong contrast to that presented in the following sketches, taken at its south side (Fig. 28). Both these sketches exhibit the rounded, clean-swept bosses of true glacier ice characteristic of the southern side of the Tongue. They also show two deep indents, of which the western, next the coast, is several miles in length, trending from south TOV) UOSMVTT OY JO UOISUayxXe pPAvALES oY SuTEq ‘qgSu] UI SoTL g JoLOV[S Surywoy osavy v ‘onduoy, ratateg eoy prolysuepaoyy oxy Jo opis yynos ol} Woay Uses SY 43192]9 uosmeRW 330009 ssne9iw pudsmyau9,W 82{ JUOWPaIlg spura neagetd on} Aq pues paezziiq eyg Aq Ajoatqoedsea opvUl LSNAYSUS JO SOS OMY SUTMOYS ‘MOUS PAVY YITM padoAOD ST 4YSTI ag 09 JoLALTVG ay, ‘Adl zaelovyps aleq ST Surpurys SI punoasa10j eyy Ur amsy 94 ato Ar adoys oy, “Spalezziyq Ay.oygnos ayy Aq PaULLOF SJOTUT SUOT OY Surmoyg HOONOL UAIVUVA AOL GTIOLMSNACYON AHL FAO ACIS NUAHLNAOS WOUM MATA ‘86 P14 —- Se, ee z EE = , = ee —— * > oe ee an] eag<— - -— Ss wausseg a9] prolysuapsoy uj aajuy daag He Kea’) AesINWAW ! 4a19e19 UOSMeW, 3S.4NYa}42019 4W 3 aBeqAuniviw val4sseg pjolysuapson pue ssneoiw AOYS UIIMIAQ Jaju| daaq sparzzijq Ayaoygnos oyy Aq posneo ove oof vos OY} TO LoNAYseS OL, ‘aor guoutpard oy4 09 Surpuoosap soqoue osnY YIM ‘yoor oIsVq YL pouMOd STI NveyrTd oy cave punoadyorq oyy UT SAU V MLSAM DONIMOOT ‘ANI VAS AHL WOUd NAS SV HOONOL YALYUVd HO!l GTOLISNUCGUON WAL JO ACIS HLAOS ‘0 “1 = a 3000S ssnen aw pukmqay aW 74 GLACIOLOGY northwards, and due to marine erosion effected, when the sea is free of ice, by the fierce blizzard winds. Fig. 30 shows, amongst other things, the numerous and large sastrugi raised there by the southerly blizzards. The blizzard first breaks up the sea ice, then piles it as drift pack against the southern side of the Tongue. The jagged tilted slabs of this pack ice shelter the drifting snow, and give origin to sastrugi of exceptional size. It is obvious that the drift snow which has helped to round off the weather side of this Tongue is carried in enormous quantities across it, forming immense drifts to leeward, that is, on its northern side. It may be suggested that these drifts, forming at first on sea ice, if the sea ice does not break away the same year, may eventually pass into a species of barrier formation, partly ice, partly old snow. That this Tongue is afloat is, we think, proved by the entire absence of any trace of tide-crack at its southern side. Along its northern side the sea ice was shghtly cracked, but probably this was merely due to small differential movements between the sea ice and the Tongue, as, even if they both rise and fall together with the tides, the inertia of the latter is so much greater than that of the sea ice, that some cracking of the sea ice at its junction with the Tongue may be reasonably expected. We conclude, therefore, provisionally that this ice is afloat. A glance at the plan and the sketches shows that it is not only the blizzard wind which drifts snow over the Tongue, but the plateau wind also. The latter wind blows from off the plateau coastwards down the depression of the Mawson Glacier, and tends to build the Nordenskjéld out in an easterly direction. This plateau wind blows from a direction about W. 10° N. The following plan and cross section indicate the probable structure of the Tongue (Fig. 31). The surface of the Nordenskjéld Ice Tongue is on the whole very flat and even, in striking contrast in this respect to the Drygalski. In the area between the rounded hummocks of greenish ice forming its southern margin and the consolidated layers of old snow forming its northern edge the surface is formed entirely of hard snow covered with a thin glaze, due to thawing and re- freezing of the snow. Its surface shows broad, but very gentle, undulations, with intervals of about a quarter of a mile between the summit of one undulation and that of the next. Here and there, especially near its southern margin, hummocky sastrugi project 5 or 6 feet above its general surface. Towards the centre of the Tongue the sastrugi are comparatively insignificant, only a few inches in height. Certainly the plateau wind in this neighbourhood is quite subordinate in force to the southerly blizzards, as far as one can judge from the sastrugi. This is the reverse of what is the case near the Drygalski. The plateau wind would, therefore, scarcely be strong enough to ze Piedmont 3 * Glacier Ice. © ; ROSS SEA CHARCOT BAY Cape Bruce : Drift \“Snow ~~ plateau Sastrug! Tanne __NORDENSKJOLD vb aid Glacier sce | ICE BARRIER ee =~ \ TONGUE PEON pis ea Tz ZS oa g —_- Pa\se 8 8 : mS? AWS N. Mt Gauss - M' Chetwynd == ' Piedmont 5000 feet. ===~- \ Glacier Ice Alt StatuteMiles 2 _' # 8 4 5 6 7 8 lL EAST. o> a Cape Bruce Probable old drift snow L4 BRN on glacier ice or old sea ice. a ~ NE = = lp 77~=5M<7X\ ONORDENSKJOLD «BARRIER | Nie Se ies SS ¢ = — G - as Se (a Tif oo x . \ ee op. - < - = th Te Gs = pee 42 ee ra eed =. OV Fae GL er oa = = ava Fre Sus fasts tata Obable 4 a 4aae . ~Nags 2 4 20% 4 eat ssacee 7: e, Probable old drift snow NORTH. onglacier ice or old sea ice SOUTH. | NORDENSKJOLD BARRIER [ieee Glacier Ice Ta ar Probable morainic material Longitudinal Scale. Vertical Scale. peer eu oes) pe Se Xe Seatuce Miles rm ir ce ne Te tO . Fie. 31. PLAN AND SECTIONS OF THE NORDENSKJOLD ICE BARRIER TONGUE The plan is after Mawson, with slight modifications 76 GLACIOLOGY remove the snow drifted to the north of the Nordenskjild Barrier by the southerly blizzards. It is suggested in the sketch sections that at the eastern end of the Tongue, and along its northern margin, the drifted snow resting on thin glacier ice, or old sea ice, may in itself form the bulk of the Tongue there for some distance inwards from the sea cliff. If the width of the Mawson Glacier, as shown on the plan, be compared with that of the Nordenskjéld Ice Tongue, the widths agree so closely that it seems unlikely that any considerable addition can have been made to the Tongue there by drift snow. There can be little doubt that along this northern edge, where the height of the ice-cliff is only 50 feet, snow must contribute to form some part of it. A question which the plan of this Tongue at once suggests is, in view of the thinness of the neck by which it is attached to the Mawson Glacier, why does not the whole mass break off bodily and float away? Unfortunately time did not admit of our examining its inland end. It is probable that its western end is aground, either on a rock bottom, or more probably on its own bottom moraine, or fluvio-glacial bank. There are slight traces of crevasses to be seen only near the southern margin. It appears to represent a senile stage in the history of a glacier afloat, once part of a large piedmont aground. The next sketch shows a deep valley, the Cotton Valley, which comes in to join the Mawson Glacier Valley near the base of Mount Murray. Hills Cle M® Murray coon Valley North + comin GiaNaviaiacler Capen: jay join the Me Mawson Glacier val Valley Glacier Ice onSouth side Low rock CVT choming Evidence a ee 3 Glacier ice of acaen Mowson ono of having been strongly ‘glaciated. Nordenskjold fide, Fre. 32 West coast of Ross Sea, looking west, at point on sea ice 13 miles south of the Nordenskjéld Ice Tongue From this sketch it would appear that the Nordenskjéld Ice Tongue is all but detached from the Mawson Glacier. In the next sketch (Fig. 33), 5 miles south of the Nordenskjold Barrier, thick masses of piedmont aground are seen between the coast and Mount Chet- wynd (5000 feet). A deep ravine (ice barranca) intersected the piedmont near the coast to the right of Mount Chetwynd. At the point where the dark capping is seen on the right of the section there was an appearance suggestive of a cirque. There can be little doubt that here there is a great thickness of basic rock, overlying what appears to be a sedimentary THE COAST SOUTH OF THE NORDENSKJOLD ICE TONGUE 77 formation, which rests in turn on a foundation of granite rock. To the left of the section are two long and deep glacier valleys. The right-hand valley, the Fry Glacier Valley, is of the nature of an outlet glacier. When we were looking directly up it we could see that it cut its way right across the horst, and apparently ascended to the snow-fields at the back of the plateau. It is a long, narrow glacier with straight, clean-cut rock walls, resembling in general appearance those of the Ferrar Glacier. The granite mountain which lies immediately in the foreground to its right Dark blackish brown to black rock Mt Chetwynd Gauss Mawson Glacter of high plateau 5000 Dork blackish rock, Geyoad OMS pledurent. mont frock Nonatak | Maife-edged aréte : Perhaps a sill or lave : : : : H : ; ; : Barrance Sea lee Predmoat Glacier Ice with convex surface Piedmont glacier ice with plateau hills behind, at 13 miles south of Nordenskjéld Ice Barrier Tongue Penck Glacier Glacier M* Creak f Black rock, either 2 basic sill ora platen basalt, ier ey henna’ bong trenched glacier valley : sh rock perhaps $ glacier valley. og ph raged gece rr ] Seabed keddstone Or oder ' ‘ { Piedmont ice. Trip Istona poout 2 miles ¥ ef Depot Island. Fic. 33. West coast of Ross Sea, at 22 miles south of Nordenskjéld Ice Barrier Tongue, from the Penck Glacier northwards, showing a continuation of the piedmont ice with stratified rocks, probably Beacon Sandstone, to the right. Piedmont ascends to over 1000 feet before it reaches the foothills of plateau rocks had evidently been intensely glaciated, as also has Tripp Island, off the mouth of the Penck Glacier.* The latter appeared more to resemble an alpine glacier. It was very deeply entrenched, but did not appear to cut right through the horst. Plate XV. we owe to the faithful copying with great accuracy by Mr. K. Craigie of a negative much too faint to yield a satisfactory print. The glacier behind the cyclometer of the sledge is the Penck Glacier. The Fry Glacier * It is doubtful whether this sketch, made in 1908, is correct in showing Tripp Island so close to the piedmont. Priestley found in 1912 that Tripp Island was surrounded by sea ice, and about 2 miles distant from the nearest piedmont. There can be no doubt that the piedmont has shrunk noticeably between 1908 and 1912. L 78 GLACIOLOGY junctions with the Penck between the two headlands to the left of the left-hand figure. Depot Island appears to form the eastern limb of a strong anticline in the gneissic granite. It is remarkable for the extraordinary numbers of large enclosures of a diorite containing very large crystals of sphene.* Large enclosures of quartzite, up to fully 10 feet in length, are present in the gneissic granite of the western limb of the anticline, Boa ASty Rocky Headland capped by thin ice Depotlisland. — ~ DENUDED ANTICLINE~_ >, ~ about 200 Ft above sea. 140 Fe above sea Ya Be $ as ; ; Gneissic Granite with large 7 = 7 > = am a : enclosures of ghorite. LS is eG 3 Depot .+ , 4a: si = - — == : = Bern closurcsia——a = Toa ae aS Soe ae = E of greenish grey quartzite = = ~ 7 oes Jaci See (oF? long by SF thick,and =~ — OCC ee = —. thinly laminated in ~~ - oar gneissic granite. Fie. 34. VIEW LOOKING SOUTH Depot Island and the adjacent headland to the south, Cape Ross, have both been intensely glaciated. Depot Island is 140 feet above the sea, and Cape Ross about 200 feet. An interesting feature at this point, and from here to Granite Harbour, 15 miles farther to the south, is that the piedmont, which is here extensively developed, is clearly seen to rest for considerable distances on a solid platform of granite. Cape Ross, 2 miles south of Depot Island, is formed of gneissic granite, with Cape Ross Depot Island, -- ~~ Sea lee ss , Fie. 35. VIEW OF COAST NEAR DEPOT ISLAND Taken from point 2 miles 300 yards to the south of the island dark grey bands rich in biotite, and with light veins of coarse pegmatite and porphyritic crystals of felspar. The cape is intersected by two sets of dykes, one set of a hornblendic-lamprophyre type, the other yet to be determined. The general appearance of this gneiss is shown on Fig. 36. At a small rocky point about 5 miles farther south, midway between Cape Ross and Gregory Point, we examined the piedmont ice where it rested on the granite * A photograph by Mawson showing these enclosures is given in his petrological volume of this Memoir. PLATE XV Fic. 1. WEST COAST OF ROSS SEA With Penck Glacier on left, and plateau hills with large cirque on right Fic. 2. VIEW TAKEN FROM SEA ICE Looking south towards northern edge of the Nordenskjold Ice Barrier Tongue. Height of cliff 50 feet. [D. Mawson [Zo Face p. 78 COAST NEAR CAPE ROSS 79 platform. The granite cliffs here were low, approximately about 50 feet high. We found the edge of the piedmont ice here about a quarter of a mile back from the cliff face. We found a gully, as seen in the sketch, cut out of the solid granite toa depth of about 20 to 30 feet. It seemed of the nature of a huge glacial grove. It trended -| Hornblende -Biotite Gneiss 7084 INOFDY Porphyritic dark streak Fic. 36. GNEISSIC GRANITE AT CAPE ROSS, TWO MILES SOUTH OF DEPOT ISLAND from about W. by 8. or W.S.W. to E. by N. or E.N.E. The gully, although the piedmont had evidently retreated quite recently, had no sign of boulder clay in it, but the bottom of the gully and the rock platform above it on either side was strewn with large erratics, for the most part very much rounded, and suggestive of bottom moraine. ‘The ice of the piedmont at its retreating edge seemed on the whole fairly Piedmont Glacier about % mile back from cliff face eo ae, A= CUFF OF gneIsSiC gramice Erratics se * ae eg SR ES > <7 LIS az Foul 50 100 Feet high = Basic Oyke Fie. 37. GLACIER-CUT CHANNEL IN GNEISSIC GRANITE Exposed to view through very recent retreat of piedmont, 7 miles south of Depot Island tree from rock sediment, but was too much concealed under old snow to yield a good section. Resting on the top of the gneiss platform, from which the piedmont is now rapidly retreating, were numbers of erratics, and amongst them a large boulder of granite, shown in the sketch below (Fig. 38). It exhibits rocks of three different ages. First and oldest, a dark greenish-grey 80 GLACIOLOGY porphyritic gneiss. This has been cut by veins of fine-grained reddish granite with green mica. These veins in turn have been intersected by coarse red aplites. The patch at the top left-hand side of the block is not another variety of rock, but simply another face of the boulder. If this greenish-grey porphyritic gneiss is of the same age as the gneissic Fine grained reddish granite with green mica. Coarse red aplite . Dark greenish grey porphyritic gneiss. Fic. 38 eranite of Cape Ross, and the latter is the equivalent of the gneissic granite of Depot Island, we have here evidence of the following succession amongst the eruptives, the oldest being mentioned first :-— 1. Basie sphene-diorite. 2. Grey gneissic granite. 3. (a) Fine-grained reddish granite with green mica ; () coarse red aplite. These last two rocks probably belong to the important group of the red granites so widely distributed along this coast. The next sketch, at about 11 miles south of Depot Island, is taken from the sea ice off Gregory Point. GRANITE MARI It shows the general appearance of the piedmont aground, resting on its low- lying coastal platform, formed here of intensely glaciated granite. It has a width here of about 7 to 8 miles. GRANITE HARBOUR 81 At Gregory Point it terminates against the area glaciated by the Mackay Glacier and the Bonney Valley and Glacier. Next, at 15 miles south of Depot Island, we reach Granite Harbour, a magni- ficent inlet, with the Mackay Glacier at its head. This glacier lies in a very typical over-deepened valley, with a far wider valley above, lying at a height of about 1500 feet above the present surface of the ice of the Mackay Glacier. The sketches * speak for themselves as to this evidence, and better testimony is borne by the excellent photographs of the Discovery Expedition (National Antarctic Expe- dition, 1901-4, Plate XXXVI. Figs. 1, 2, and 3). Figure 3 particularly shows extremely well the great terrace of the wide original valley above the over- deepened valley, with the strongly facetted hills rising above this upper terrace. The spectacle afforded by the Granite Harbour is truly magnificent, and most impressive and interesting for students of ice and its work. The sheer glacier- cut walls on the north side of the Mackay Glacier and Granite Harbour, and the steep slopes of the rocks bounding the over-deepened valley on the south, show that the present glacier must extend much below sea-level. As no complete set of soundings f were obtained at the head of the bay in which the glacier lis, it is impossible to form more than a rough guess at this thickness, but the angle of slope of the rocks on either side of the valley and the height of the ice cliff at its seaward end being taken as some criterion, it is probably of the order of somewhere about 1000 feet. Ice-falls were conspicuous, crossing the valley just below the remarkable line of nunataks. The wonderful nunatak, Suess Nunatak, shows, as seen in the sketches, two vast glacier-scooped concave surfaces respectively on its northern and southern sides, and a conspicuous hollow occupied by a small snow- field at its summit. Suess Nunatak could be seen to be formed of some black rock, probably part of a dolerite sill. Higher up the valley, to the right, stratified rocks, evidently of the Beacon Sandstone formation, make their appearance, traversed by dark dykes and sills. The cross section of this remarkable valley, based on Mawson’s theodolite determinations from distances which varied from 5 to 10 miles, is shown in Fig. 40. The following three sketches were made successively from north to south, the uppermost sketch representing the northernmost view. There can be little doubt that the ancestor of the Mackay Glacier during the maximum glaciation had a cross section at least six or seven times the area of the present glacier. Without discussing the whole question of over-deepened valleys here, or the origin of the great upper terrace, it may be remarked that so far as the area * The focal plane of our camera refusing to work in the great cold at the time of our visit in October, we had to rely on sketches only. + H. T. Ferrar states, in Nat, Ant. Ex. Natural History, vol. i, Geology, p. 94, “ This harbour is fiord like, and has depths of over 100 fathoms within a quarter of a mile of the shore.” 82 GLACIOLOGY examined by us is concerned, it appears that during the maximum glaciation the whole of the old U-shaped valley, 10 miles in width, was filled with glacier ice to a depth of at least 1500 feet. The upper terrace may have been, no doubt has been, subsequently modified by cirque glaciers, but it was probably not cirque glaciers which originally excavated this gigantic terrace. The evidence of the erratics proves that at Ross Island the whole level of the Ross Barrier in that region was formerly 900 feet higher than at present, the Ferrar Glacier perhaps 3000 feet higher, the Beardmore Glacier 2000 feet higher.* In the face of this evidence, as well as of the complete over-riding with glacier ice during maximum glaciation of the Larsen, Bellinghausen, Crummer, and Priestley Massif, to heights of at least 1500 feet above the present surface of the adjacent glaciers, the valley of Granite Harbour must necessarily have been almost completely filled with ice far above the Mountain near M*‘ England. about 4000 Ft high. Mt England Suess Nunatak AAG ‘ M'Marston ‘ ‘* “Granite with oaatsac poe Ls lt fs -aykes & sills Si eee ERO ; EON ee = ‘e+ Sof dolerite. Sea level. at NG WY Longitudinal Scale vssuui __?@ 3. 4 Statute miles. Vertical Scale Cee CFE: Fic. 40. SECTION ACROSS MACKAY GLACIER, SHOWING WELL-MARKED, OVER-DEEPENED VALLEY The “ trogschulter ” to right of the glacier is about 800 feet above sea-level level of the great terrace. The facetting of the rock-spurs which rise considerably above the level of the terrace is also very conspicuous. At Cape Roberts, just to the south of the entrance to Granite Harbour, a low headland of gneiss shows evidence of having been lately striated by ice coming from a direction of about W. 10° S. Numerous erratics of kenyte of some size were lying on this headland at about 20 to 30 feet above sea-level. They may have been transported by floating ice from Ross Island during the recent submergence of the coast, of which the raised beaches are evidence. Fifteen miles 8.8.E. of Cape Roberts is Dunlop Island (Fig. 41). The strait which separates Dunlop Island from the mainland, about 1 mile in length and } ofa mile in width, is very suggestive of a glacial valley formed by the * Suess Nunatak, rising fully 2000 feet above the level of the adjacent Mackay Glacier, has been glaciated over its summit, which indicates a former greater thickness of ice in this valley as compared with its present thickness of about 2000 feet. PLATE XVI GRANITE HARBOUR AND THE MACKAY GLACIER Lying in an over-deepened valley, with the wide “alb” valley formed chiefly by the “ ice-flood,” when at its maximum To face p. 82 P DUNLOP ISLAND 83 ancient Ross Barrier when it over-rode the whole of this region. Glacial valleys probably excavated by the same agent are to be seen at Cape Royds. Since the retreat of the Ross Barrier the piedmont ice has pushed across the strait and glaciated the gneissic granite in sitw on the island in a direction from about Wr 3a) Sato He 35°-N. The island is formed of shingle and redistributed glacial boulders and gravel. The gravel is formed of small pebbles about half an inch in diameter, and the boulders are mostly from 3 inches up to 18 inches in diameter. Scale of Plan. N Oe ee OEE Chairs Dunlop Island Gneissic Granite Terraced glacial gravels Striated from resting on gneissic granite ajiuesB y991aU6 Guthj4aa0 31 Juowpald | ” Gneissic granite ° 50 100 200 longitudinal Scale Sa ae Vertical Scale Cs...2 __00_ SN Feet Piedmont glacier ice ~ resting on gneissic granite Dunlop Island. 40 Lonaitudinal Scale Rae _____ chains. VercicallSCalemn aire eee, Fic. 41 One boulder of granite measured 6 by 5 by 3 feet. Its upper surface is strongly grooved in a south-east and north-west direction. These main grooves are crossed by another set coming from about W. 35°S., the direc- tion of glaciation followed most recently by the piedmont ice subsequent to the retreat of the Ross Barrier. The north-west to south-east grooves pointed straight to Hut Point, 60 miles distant to the south-east, and it may be significant that a few fragments of scoriaceous basalt and dense olivine basalt, both of which occur 7 situ at Hut Point, were found here by our colleague, Dr. Mackay, among the boulders. We think it may be concluded that the strait which separates Dunlop Island from the main- 84 GLACIOLOGY land was probably formed by the Ross Barrier. The coarse and fine gravels form- ing the greater part of the island have probably been formed from glacial material redistributed in sea water subsequent to the retreat of the barrier, and during a submergence of 100 feet or upwards. At some time during this submergence the gravel and boulder bank must have been over-ridden by the glacier ice of the piedmont, and the large granite boulder firmly imbedded in the bank became cross- striated. Then the piedmont ice retreated, and during re-emergence tidal scour has separated the large gravel bank from the mainland, and has terraced the side nearest the strait. To the south of Dunlop Island the piedmont ice is very extensively developed, covering a large area inland to at least as far south as New Harbour. The general appearance of this part of the coast is shown in a photograph by the Discovery Expedition (National Antarctic Expedition, 1901-4, Album of Photographs and Sketches, Plate XX XIII. Fig. 3, photo by L. C. Bernacchi). To the north of Marble Point we observed at least three low outcrops of granite peeping out from beneath the piedmont. The piedmont therefore is still resting on a coastal platform formed largely of rock. (Marble Point is formed of cale-schist and contorted mica-schist intruded by epidotic granite and aplite.) At Cape Bernacchi,* a few hundred yards to the south-west of the rocky point, the shore is strongly terraced. The following section was then measured there by the Northern Party :— Mounds OF angular rock fragments, l inch to 2inches in diameter. loo Ft terrace. 40 Ff terrace. Bottom moraine 2 20 Ff terrace. Ice Foot . Sea Ice. Crystalline graphitic marbles , tourmaline. schist and garnetiferous intrusive aplite. Fic. 42, SECTION SHOWING TERRACES AT CAPE BERNACCHI The total length of the section is about 300 yards The lower terrace is composed of heavily glaciated pebbles and boulders, with occasional erratics up to 5 feet in diameter. This appears to have been pushed along under an ice sheet. The middle terrace is formed of Pre-Cambrian or possibly Cambrian crystalline * Cape Bernacchi is formed of coarsely crystalline saccharoidal marble with graphite flakes, and also of schorlaceous schist. Both are strongly intruded by whitish granites. A good deal of epidote has been produced along the planes of contact. CAPE BERNACCHI 85 rocks intruded by aplites, and the top terrace is built of angular material, the fragments being only from 1 inch to 2 inches in diameter. This material is irregularly heaped together in small mounds. The two lower terraces are very suggestive of recent emergence of the land, but marine fossils were not observed here, but were discovered by one of us (R. E. Priestley) at Dry Valley, about 12 miles to the south-west. M CHAPTER V GLACIOLOGY (continued) THE FERRAR GLACIER AND CAPE ROYDS AREA THE FERRAR GLACIER AND DRY VALLEY WE now approach the southern end of the low-lying part of the great horst. As already stated, this relatively low-lying part extends from Mount Nansen on the north to the Royal Society Range on the south. The Royal Society Range is a huge horst within a horst, rising to altitudes of over 12,000 feet above sea-level. The precise trend of the tectonic disturbances which cause the downthrow to the north of the Royal Society Range is not known, but the great fracture on which Mounts Erebus, Terra Nova, and Terror are situated trends nearly due east and west. This fault line should intersect the west shore of McMurdo Sound between Cape Bernacchi and New Harbour. The huge massif of the Royal Society Range shoulders away the inland ice streams, compelling them to make a long detour in part to the south through the Skelton Inlet, in part to the north through the Ferrar Glacier and its branches. For a distance of at least 30 miles south of the Ferrar Glacier (possibly 50 miles, if the Koettlitz Glacier is not an outlet glacier from the plateau) there is no breach in this mighty wall of rock. This stemming action, forcing the inland ice streams to flow along lines of weakness in the rocks induced by parallel faulting just north of the Royal Society Range, contributes to make this area an important outlet region. An examination of Ferrar’s geological map shows that the lower part of the Ferrar Glacier, with its trend prolonged inland up the glacier South Arm, the North Fork Glacier with Dry Valley, and three other valleys which adjoin it in succession northward, together with the Mackay Glacier, have an approximately parallel trend. This trend is about E.N.E., with a tendency to become more easterly as Granite Harbour is approached. For the upper 50 miles of its course the Ferrar Glacier has a W.N.W. to E.S.E. trend. It is clear from the physiography of the district that the Ferrar Glacier is now but a shrunken remnant of its former self. Ferrar states* in speaking about the corrie glaciers at the north side of the head of the Ferrar Glacier at the Inland Forts, ‘“ All flow southwards, but fail to reach the ice of the main valley, and are now building up crescentic moraines at * National Ant. Ex., Geology, p. 73. 86 THE FERRAR GLACIER 87 their terminations. The interest of the glaciers lies in the fact that, though they now flow southward, they were formerly forced northward by the Ferrar Glacier into another drainage system.” The same remark may be made about the Valley of the Blue Glacier. That wonderful spurless valley was probably excavated by a former branch of the Ferrar Glacier escaping over the rock ridge at Descent Pass. If this view is correct, the height of Descent Pass above the present level of the adjacent ice of the Ferrar Glacier is some roughly approximate measure of the recent shrinkage of the ice in that region. The exact height of Descent Pass is not given on the Section 1 of Plate VII. (op. cit.), but to judge from the scale is about 2000 feet above the present level of the glacier. The bold headland of Solitary Rocks, in itself too small to harbour sufficient ice for self-glaciation, has obviously been intensely glaciated in recent time over its summit. This rises tans : Su about 2000 feet above the level of the = Nunatak adjacent ice. PLAN SHOWING THE FOUR OUTLETS OF THE FERRAR GLACIER DURING Depot Nunatak, at the head of the ICE MAXIMUM. glacier, is obviously an ice-flood gauge on a small scale, and its strongly glaciated summit stands 500 feet above the level of the adjacent ice. It follows that 2000 feet indicates the very minimum former height of the glacier ice in the Ferrar 5 9 ay EN Yes ~ Valley above its present altitude. In an SEP GA earlier paper * Ferrar estimated the former o ) Muster height of ice in the Ferrar Glacier Valley as 3000 feet above its present limits. The modern Ferrar Glacier system thus Fie. 43 resembles the disintegrated drainage at the delta of some large river. The Ferrar formerly discharged ice into the sea from four mouths—the Blue Glacier, the East Fork, Dry Valley, and an as yet unnamed valley to the north which took off the drainage of the ice near the Inland Forts towards Dunlop Island.t Diagrammatically this drainage is represented on the sketch map Fig. 43. An excellent account of this important outlet or spillway glacier has already been furnished by H. T. Ferrar. The additional information now given was obtained by the Western Party on their journeys up the Ferrar Glacier and up Dry Valley. The discovery was made that the Solitary Rocks are not islands, but are connected with the north wall of the glacier by a ridge of granite over a thousand feet high. * Roy. Geogr. Jour. + This has subsequently been named Wright Glacier by T. Griffith Taylor of Scott’s Expedition. 88 GLACIOLOGY It was also concluded that the Solitary Rocks were not capped by Beacon Sandstone, but wholly formed of granite.* The Solitary Rocks were proved by an actual traverse to be the butt-end of a peninsula banking up the ice above and forcing it round to the southern side, where it descends in a series of ice-falls. Access was gained to the Solitary Rocks at two points. These consist of alter- nate bands of black and yellow rock, which are identified on Ferrar’s map as dolerite and Beacon Sandstone ; but on December 22nd, on climbing down the ice-cliff and crossing the frozen stream at the foot of the cliff, and climbing up the talus acree and collecting from the lower yellow band of the Northern Solitary, the observer found the rock to be a granite similar to that of the Kukri Hills. From this note about the alteration of the geological boundaries we may pass on to a general description of the Ferrar Glacier. The entrance to the Ferrar Glacier Valley, seen above, is about 5 miles in width. The facetted character of the steep walls of the valley, the entire absence of over- lapping spurs, the resemblance of the whole valley to a vast, slightly curved groove + gouged out of the plateau to a depth of fully 6000 feet, bear strong testimony to the vast power of its réle in the evolution of earth forms in Antarctica. THE FERRAR GLACIER The following description is based on the observations of the Western Party, Armytage, Brocklehurst, and Priestley. The lower 10 miles of the Ferrar Glacier, below the first ice-falls, consists of ice which, as far as we could judge from the surface, is not glacier ice, and it seems probable that the present end of the true glacier is at those same ice-falls. The junction between the sea ice and the commencement of this ice is sometimes a distinct cliff several feet high, against which snow-drifts are banked, but more commonly a gradual slope. It appeared, even on our outward journey, that this ice was truly crystalline ice, due to the re-freezing of thaw-water containing large quantities of half-melted snow. The surface just above the commencement of the ice is, on those patches where it is free from snow, exactly comparable with that of the southern half of Blue Lake, Cape Royds. The hexagonal ice is very prominent, and forms in places almost spherical patches many feet in diameter, and with a convex surface which is sometimes formed of beautifully regular hexagons, or, when the crystallisation is less regular, of frond-like masses of crystals of all shapes, generally * The view that the Solitary Rocks were an isolated nunatak and were capped by Beacon Sandstone was exactly the conclusion that one of us (Priestley) favoured when seeing the mass as it presented itself to the sledging parties of the Discovery Expedition. It was only a closer sub- sequent examination from a different view-point that proved this inference to be incorrect. + Nussbaum’s expression, ““Wie mit ein Hohleisen auf einmal ausgearbeitet,”’ seems strictly applicable to this valley. PLATE XVII Fic. 1. ENTRANCE TO FERRAR GLACIER, LOOKING WEST OVER THE SEA ICE Fic. 2. EFFECT OF THAW. FERRAR GLACIER AT THE SOLITARY ROCKS, WESTERN MOUNTAINS [Photo by Brocklehurst [ Zo face p: 8S THE FERRAR GLACIER 89 roughly hexagonal, similar to the ice photographed at Clear Lake. When the hexagonal ice has been removed by ablation, snow-tabloids and bubbles of various size are common, and occasionally the secondary ablation-formed ripple surfaces so common at Cape Royds are developed. At other places there appears to be a development of what is either coarse granular névd or minutely hexagonal ice. As the ice-falls were approached the bare surfaces became fewer, and finally disappeared until the ice was covered with several feet of snow, the upper foot more or less hardened into a crust, whilst underneath this crust was at least 3 feet of loose, largely-granular snow. At this place the pressure from the glacier above had caused considerable undulations in the surfaces, and we passed several crevasses. We had a fairly clear glimpse down one of these crevasses, and the structure of its walls was very puzzling. Instead of the uniform sheet of ice that was to be expected, the portion of the walls exposed to our view seemed to consist of flattened lenticles of ice with layers of snow in between, and it was not until the return journey that any explanation of this peculiar structure was suggested. On the way back to Butter Point we passed this part of the valley during a very hot summer’s day, when the thaw was most powerful, and almost the whole of the surface for several miles below the ice-falls was occupied by a series of pools of thaw-water full of drift snow, and it seems probable that this thaw explains both the ice surface we passed over and the structure of the crevasse walls. Under the ice formed in this manner there may be a substratum either of glacier ice or of sea ice, but every piece of evidence points to the probability of the first few feet at any rate being formed in the way just described. Above the ice-falls the true glacier ice set in, but very little of ice or névé was exposed for some miles, as the surface of the glacier was hidden under a uniform coating of snow. For some time before any surface moraine was reached the presence of an englacial one was indicated by numbers of circular patches of hexagonal ice indicat- ing where the boulders of the moraine had sunk beneath the surface. Always we found that, when a moraine had persisted for some distance without being fed from other moraines or from the cliffs under which it had passed, the number of boulders above the surface became less and less, until the moraine had become wholly englacial. It is an interesting fact that the hexagonal structure in the ice was never present when the boulder had just sunk beneath the surface, but was only superinduced after the frozen thaw-water had been formed a long time. It seems therefore to be a secondary structure, due either to a molecular change in the thaw-water ice itself, or to the re-crystallisation of the lower portions of the snow-drift collected in the depression usually left where the boulder had disappeared. Another feature very well marked at this time was the recementation of old eracks and narrow crevasses by the thaw-water, with a distinct and very fine lamination parallel with the crack. The same thing occurred in the lakes at Cape 90 GLACIOLOGY Royds, and was particularly noticeable in one or two of the master-cracks of Coast Lake. In crossing the glacier from north to south, opposite the lower Cathedral Rock, we crossed three moraines, and could see one more lateral moraine along the south side of the glacier below Descent Pass. We followed the strongest of these moraines for some distance, but beyond Descent Pass it made a sharp bend to the south, and became lateral, or sub-lateral, along the upper Cathedral Rocks, having evidently been pushed out below by the ice coming down from Descent Pass. A few miles above the Cathedral Rocks is another series of heavy ice-falls ; the ice immediately beneath them is seamed with two series of strain-cracks, those in the series parallel to the length of the glacier being by far the most numerous. The other series is at right angles to the first. A similar structure was observed between D bluff and the Solitary Rocks in the northern lobe of the glacier where the ice slopes sharply towards its northern edge. A series of parallel compound cracks cross it diagonally from the upper Solitary Rock towards the lower end of the D bluff. The transverse cracks forming the compound diagonal ones increase in width, as they move towards the north, until many of them join up, forming long crevasses. These transverse cracks vary in width from mere lines to crevasses 2 feet wide. The only occasion on which sounds, suggestive of appreciable movement of the glacier ice, were heard was in a camp at the foot of the ice-falls which force their way around the southern side of the Solitary Rocks. The ice here, owing to the narrow- ing of the valley, is subjected to tremendous pressure, and rather fine ice-falls are developed. From the ice all round our tent sounds like pistol-shots and the popping of champagne corks were heard, evidently caused by the ice relieving strain by fracturing, and the strain structure mentioned as occurring below the second ice-falls was also very prominent. EFFECTS OF THE THAW ON THE ICE OF THE FERRAR GLACIER Plate XVIII. Fig. 1 shows the effect of the thaw, about Christmas time 1908, near the Solitary Rocks in the Ferrar Glacier Valley. The effect of the thaw depends of course on the amount of direct sun’s heat, and largely on the state of the atmospheric currents, as well as on radiation of heat from rock and rock dust. The conditions most favourable seem to be two or three calm days with a full allowance of sunshine. At the end of such a period the thermometer we had registered 40° F. at the end of the second day, and the glacier appeared to be melting under our feet. The thaw, on the other hand, practically ceases, except locally under favourable conditions, when the cold overflow breeze from the plateau has been blowing for a good many hours. Its effects were so PLATE XVIIT Fie. 1. RIVER OF THAW WATER AT SOLITARY ROCKS, FERRAR GLACIER [Photo by Brocklehurst Fic. 2. HANGING GLACIER OR CLIFF GLACIER A tributary of the Ferrar Glacier at the Cathedral Rocks. Dec. 28, 1908 [Photo by Brocklehurst [ Zo face Pp 90 THE FERRAR GLACIER 91 varied and so different on different occasions, that the only way to describe them fully and adequately seems to be to treat the subject more or less in narrative form. The first result noted was the formation of hollows partially filled with thaw- water round the boulders of the moraine, a process which finally has caused the disappearance from sight of whole moraines. On December 18th, 1908, opposite the upper Cathedral Rocks, we sledged for some time up a fairly steep rise of clear ice, which was seamed with small stream channels up to 2 feet in diameter, and running mostly along partly recemented crevasses and cracks. Many of the bottoms of the channels were covered with fine detritus, and in places the channels widened into round ponds, some of which contained water. The channels ran very irregularly, but seldom ran transversely across the glacier for any great distance at a time, their general trend being up and down. The 20th was fairly calm with flaky snow, and by the morning of the 21st there was 2 inches of snow on the ground, and when the sun began to play on the walls of the valley, the thaw set in in good earnest. We reached the north wall of the glacier at five o’clock in the afternoon of the 21st, and were pulled up short by a precipice between 200 and 300 feet high. At the foot of the glacier ran a river 20 or 30 yards wide, and on the face of the glacier considerable thawing was taking place. Every deeper crack and boulder hole was filled with water, and this water could be heard streaming down the face of the glacier to the stream which was roaring beneath the ice-cliff. The effect of the radiation from large rock masses is strikingly illustrated at the Solitary Rocks. The ice is separated from the rock by a gully about 50 feet deep, with a stream flowing at the bottom. Next comes the lateral moraine, which is very thick, and still within the region in which the rock-heat is felt. The combined influence of the rock material of the moraine and the radiation from the Solitary Rocks has been to melt the surface of the glacier until the part occupied by the moraine forms a depression from 3 to 6 feet below the level of the main glacier surface, which commences as a convex rise so abrupt as to be almost perpen- dicular. After this the ordinary billowy surface sets in, and the next stones met with form a sub-medial moraine, which is not sufficiently thick to effect any general lowering of the surface, although each stone is surrounded by its own hollow filled with thaw-water, and along the middle meanders a small stream filled with morainic gravel, which has cut a channel about a foot deep through the glacier ice. The thaw reached its height the same day, and the notes taken on the spot are as follows :— “An almost incredible amount of ice must be being removed as water. The ground everywhere is honeyecombed with large circular holes full of water, with the large boulders or smaller morainic matter at the bottom. These holes vary from the size of pin heads to large hollows 6 or 8 feet in diameter and a couple of feet in depth. In those which have become deep enough for the water to be shaded from 92 GLACIOLOGY the direct rays of the sun a re-freezing process has set in, long acicular needles of ice forming from the small grains of gravel and crossing and recrossing in the most beautiful patterns. In others we saw hexagonal plates being formed on the surface of the water, as well as the needles radiating from the sides and bottom. The last quarter or half mile of our day’s sledging we have been passing over and through a series of streams which cover the ground almost without intermission for the whole distance, and it was only by treading on the tops of the ablation ripples that we were able to keep dry, and even with that precaution we succeeded but indifferently. To the roar of rushing water which we heard from the ice-cliff now succeeds the more insidious trickle of the thousands of streams which are steadily finding their way by devious paths over the convex face of the glacier to join the main streams below. Late in the evening of the 21st of December we walked down to the edge of the glacier just at the corner made by the isthmus joining the Solitary Rocks to the mainland. At the corner of the glacier bulge, and below the granite isthmus, was a lake which was fed by at least four streams from a large hanging glacier opposite. These streams we could see from our position were yellow with silt, and a very large amount of fine detritus must be carried into the lake and on into the New Harbour Dry Valley by the stream which has its origin in the lake. A fifth stream of water could be heard flowing underneath us from one side of the Solitary Rocks, and in- numerable tributary streams were flowing over the face of the glacier cliff. By the night of the 21st the 2 inches of snow which fell during the 19th and 20th had either been removed as thaw-water, or left as a thin coating of rough ice, opaque through the inclusions of air; and the ablation-rippled surface has been much intensified, the ripples being converted into ice-waves, with several inches difference between the top of the sharp crest and the bottom of the trough.” When we awoke on the morning of the 22nd a strong cold breeze was blowing down through the gullies leading from the inland plateau, and this breeze continued until the 26th. The thaw practically ceased when the breeze sprang up (except in those districts locally affected by heat-radiation from the rocks), and no further remarkable evidences were noted until the last stages of our return down the glacier valley. During this gale ablation and the removal of snow by drift were very rapid, and the patchy snow-drifts passed on our way up had been largely reduced in size before we passed them on our way down the valley. Many, indeed, had been entirely re- moved, and the only evidences of their former occurrence were the corresponding patches of ice free from ablation ripples. The thick drifts piled against the southern side of the bluff under the peaks D,, D., and D,, Ferrar’s report, had had at least 18 inches of its upper surface removed, and sastrugi a foot or more high had been evolved. Another effect of the quick change from thaw to cold wind was the formation of a fringe of outstanding feathery ice-crystals along the margin of many of the open PLATE XIX Fie. 1. CLIFF GLACIER FALLING ON TO SURFACE OF FERRAR GLACIER Fic. 2, THAW STREAM ON THE FERRAR [To face p. 92 THE FERRAR GLACIER 93 cracks and holes; this is evidently caused by the deposition of the vapour from the holes as it cooled when escaping into the open air. On the evening of December 28th we camped at the foot of a hanging glacier east of Cathedral Rocks (Plate XVIII. Fig. 2). Along the edge of the glacier here a fair-sized stream was flowing, and this stream broadened into a lake in the depres- sion at the foot of the ice-cascade; and again a few hundred yards below it formed a pond 40 or 50 yards across. The lower lake is full of snow, and appears to have been formed in a circular depression by the silting up of loose snow-drift and the impregnation of this drift with water from the recent thaw brought down by the stream which runs through the depression. This marsh was connected with the lake at the foot of the glacier by one or two deep channels bridged with snow in places. These channels were so deep that no bottom was found with an ice axe; they are probably partially recemented crevasses acting as drainage channels for the upper lake and the thaw-water flowing into it. An interesting feature in these cliff glaciers is that while the ice is constantly descending on to the surface of the Ferrar Glacier below it does not raise any extensive mound of ice there, but is quickly absorbed into the main mass of the glacier, which meanwhile retains the same gently sloping surface as before. Another of these cliff glaciers is illustrated in the next figure, which shows the same feature. The phenomenon is on a far grander scale than would appear from the photograph, the distance from the tent in the foreground to the glacier being considerable. The height of the rock cliffs on either side is of the order of several thousands of feet. Such instances speak volumes for the plasticity of glacier ice even at somewhat cold temperatures. Overthrusting alone would fail to account for the rapid absorp- tion of these ice masses into the main glacier. On the 30th December the thaw again became powerful. All the ice we traversed was seamed with drainage channels forming an intricate network as far as eye could see on either side of our course, and between these channels the surface was honeycombed with boulder-holes, 1, 2, and even 3 feet deep, and full or partially full of water. About 2 miles above the ice-falls all the tributary channels within our sight converged into one main channel, along which flowed a stream 3 or 4 yards wide, with a bed of gravelly morainic matter; this main channel was between 1 and 2 feet deep, and had deeply undercut sides. From the edge of the ice-falls a comprehensive view of the thaw phenomena was available. Besides the stream already described there was another of equal or superior size to the south of the middle of the glacier, and to the north of it was a series of three streams, each a couple of yards wide, and within 2 or 3 yards of each other. These streams drained the middle of the glacier, and a large quantity of the water they brought down was impounded into fair-sized lakes below the ice-falls. N 94 GLACIOLOGY To the north of us a line of broken ice along the lateral moraine betrayed the presence of a stream bed sufficient to carry away thirty or forty times as much water as was draining off the middle of the glacier, while to the south the ice was furrowed by an interlacing network of streams and ponds, which rendered no explanation necessary of why ditliculty was experienced in sledging up and down that side of the ice. The southern river could be heard flowing parallel with us 10 miles farther down the valley, where it probably opens a way through the sea ice and mingles with the sea water. The lakes were met with for some miles along the valley also, and caused great inconvenience, as they were filled and covered with snow, and so constituted so many traps for our unwary feet. When collecting snow from one of the larger boulders of the moraines, at the entrance to the East Fork of the Ferrar Glacier, an interesting exaggerated example of the increase of some grains of ice at the expense of others was observed. This boulder was heaped about with snow-drifts of the loose, largely granular snow referred to in discussing the drifts in the older sea ice. Inside the drift, near the boulder, is a regular arrangement of zones, increasing in the size of the grains as the boulder is approached, until finally the grains—without cohering—reached a diameter of from one-quarter to three-eighths of an inch. In the inside 2 inches of the drift the grains had cohered and formed true ice. Pressure here is almost a negligible quantity, and the effect must be almost entirely ascribed to the heat of the sun and heat radiation from the boulders. In regard to the moraines in the upper part of the Ferrar Glacier near Solitary Rocks, several pieces of fine-grained dark basaltic rock were observed, which fact points to the occurrence of basalts among the voleanic rocks of the upper regions of the glacier. The great height up to which these ice-worn specimens were found indicates to some extent the shrinkage that has taken place in the ice of this great glacier in recent times. MORAINES IN THE EAST FORK OF THE FERRAR GLACIER VALLEY These form deposits, a portion of which is visible as a series of small hills protruding above the ice-surface, which hills, from their occurrence in a fairly straight line, appear to be the more prominent peaks of a partially submerged ridge. The hills are composed of large quantities of debris derived from the local granites and schists, and also yielding specimens of two or three varieties of tuff (consolidated voleanic ash), basalt, kenyte, and an olivine and augite-kenyte which occurs sparsely at Cape Royds, and which have been so named because it contains large porphyritic crystals of augite and olivine, besides the more common anorthoclase felspar ; and also porphyries of varieties unknown 7 situ in the valley itself. THE FERRAR GLACIER 95 Similar moraines occur at Dry Valley and at the stranded moraines. Dry Valley. The area was originally occupied by the north-eastern fork of the Ferrar Glacier, from which the ice has now retreated, and at present it is covered by a thick deposit of morainic debris. One of the most interesting features of Dry Valley is the occurrence there of a raised beach. This will be described in detail in the part of this work relating to raised beaches. It may be stated here that enormous numbers of the delicate shell Pecten Colbecki with both valves attached to each other were found in position and quite unbroken up to 50 feet above sea-level. The general appearance of this valley is shown in Plate XX. Fig. 2. There were large mud-flats bordering the ice-foot in this valley, and these reached their greatest extent where they were augmented by the deltaic material of the many streams draining the valley, and on them, a few feet above the present sea-level, numerous specimens of amphipods and sea-spiders and one small fish were secured, all in a much desiccated condition. It is not necessary to postulate a recent rise in the level of the land to account for these specimens, since in the short period when the sea is released from the control of its icy winter covering, a strong wind blowing directly into the bay would inevitably cause a rise in the level of the water sufficient to assure the submergence of those portions of the mud- flats immediately adjacent to the ice-foot. Upon the recession of the sea numerous animals would be left stranded in any slight depression in the recently covered flats, and evaporation and ablation would remove the sea water during the late summer and autumn, leaving the desiccated remains of the animals, and giving rise to an efflorescence of salt on the surface of the mud. Indeed the sequence of events might very well have been caused by the very blizzard which raged from February 20th to the 22nd, 1908, when the Nimrod was driven north. The remaining features of the Dry Valley moraines are very much a repetition of those of the Stranded Moraines, but on a much larger scale. The interesting discovery was made that at a height of between 500 and 600 feet there was an abundance of erratics foreign to the valley, namely, kenyte and basalt and tufts appertaining to these two types.* These rocks had in no wise diminished in relative proportion inland, as compared with the rocks obviously derived from the sides of the valley, or from the higher reaches of the glacier. Only two of the many thaw-water channels which furrow the district are still filled with running streams. The rest at the most are occupied only by a string of stagnant pools, while numerous depressions of smaller extent, with a heavy efflor- escence of salt coating the gravel, mark the site of former pools. The most northerly and most flourishing stream in the Dry Valley has cut a channel of 50 feet deep through the stratified gravel, the sides of which slope * The Western Party of the Scott Expedition 1910-13 have since examined this district in detail, and Debenham found kenyte and basalt zm stu in the upper reaches of the glacier. 96 GLACIOLOGY steeply at angles between 45° and 75°. The water here was unfit to drink, owing to the amount of fine sediment held in suspension. As the stream became sluggish when breaking up into numerous branches and meandering across the alluvial stretches of land at its mouth, this fine sediment could quite easily be observed settling down in sufficient quantity to add appreciably to the delta even in the course of a few days. Stranded Moraines in McMurdo Sound. The moraines are several miles long and of considerable breadth, while many of their numerous small hills reach a height of between 100 and 150 feet. They consist of a heterogeneous collection of debris of numerous varieties of rocks, and the material ranges in size from blocks containing many cubic feet of rock down to the finest dust. They are separated from the piedmont glacier which here fringes the mountains by a stream channel cut out almost to sea-level, and the water which has accomplished this erosion is evidently the result of the summer thaw, the stream being fed during that season both from the glacier and from the snow-drifts on the western side of the moraines. This stream is undercutting the ice, and from the exposures of morainic material on its western bank it appears probable that the mantle of debris continues right up to the flanks of the foothills of the west. The debris being mostly of a dark colour the amount of thaw in summer is considerable, and the whole district is seamed with stream-channels which, during the few sunny days in the height of summer, are filled with running water. Every basin-like hollow between the ridges and peaks is filled with a lake of size cor- responding with that of the hollow. In spite of the loose nature of the debris the lake basins are enabled to hold water, because at all periods of the year the ground at a depth of a few feet is frozen hard. Even in the summer the whole mass of the debris, except an outer mantle, is firmly cemented in consequence of the freezing at a slight depth of the percolating water supplied by the melting snow-drifts, Proof of this is seen where the streams have cut fairly deep channels in the moraines. In the walls of these channels lenticles of opaque ice fairly free from gravel, and varying from an inch or two to a couple of feet in thickness, are to be seen in many places, while in other places, if a few feet of the outer mantle of the stream-cliff are removed, the gravel behind is found to be firmly cemented. Most of the streams run northwards, and at the northern end of the moraines quite a thick alluvial deposit, having a strong resemblance to a series of miniature deltas, is to be seen along the ice-foot awaiting subsequent removal to the sea. The amount of material removed from the moraines in this way must be very considerable. Another agency which must be fast reducing the size of the moraines is the direct heat of the summer sun on the cliffs at the northern end. Frequently, while we were camped near the moraines, small avalanches of gravel and mud fell on to the ice-foot, and many tons of material brought down in this manner must be carried away when the ice-foot breaks up in the late summer months. The wind PLATE XX Fic. 1. 3000 FEET UP FERRAR GLACIER, SHOWING MORAINE This is at the Western Party’s Christmas Camp. 3000 feet above sea level a Bs sen ed Fic. 2. DRY VALLEY [Zo face p. 96 STRANDED MORAINES IN McMURDO SOUND 97 also plays an important part in the transport of finer material, the snow for several miles to the north of the moraines being full of grit, which is so abundant that it accelerates considerably the melting of the drift-snow and the surface of the ice. There is a much greater proportion of pebbles and large boulders in the upper layers of the morainic material than in the lower, as seen in section in the northern cliff exposures. This phenomenon is partially explained by the fact that the finer material would gradually be carried down by the thaw-water and used to increase the compactness of the lower layers at the expense of the upper ones; but in addition it is probable that when the glacier which borders the moraines was actually providing an outlet for the ice accumulating on the mountains above it, it brought down its quota of morainic material from local sources, which local material would reach the moraines rather in the condition of large fragments than as the finely divided debris which is essentially the result of the prolonged trituration for which a long journey is necessary. This latter explanation finds support in the abundance of local erratics on that portion of the moraines nearest the shore, erratics which are identical with the different great formations which crop out in the sides of the glacier furrowing the western mountains. The southernmost portion of the moraines is almost entirely composed of angular basaltic and kenyte debris on the seaward side, the local boulders becoming more common as the landward side is approached, though at the northern end of the moraines these boulders become very numerous even on the extreme seaward side. As for the material which makes up the main mass of the moraines, a great proportion of it must have come across the Sound, because while there is no evidence of any other great outburst of kenyte material besides that of Mount Erebus, large quantities of kenyte and kenytic fragmental rocks were picked up during our short stay here of the Western Party.* An important characteristic in addition to those already noted is the very isolated occurrence of some of the erratics. Some small conical heaps consisting entirely of fragments of one kind of rock were undoubtedly, from the angular nature of the fragments, the final results of the frost-weathering of very large original blocks. Not so in all cases, however. In the case of one basalt tuff particularly I noticed that it was found entirely covering two or three small hills at the south-eastern corner of the moraines, and it was found nowhere else. The pieces were all rounded or sub-angular, and they were too scattered to have been the result of the weathering of a few large boulders. One fact points to recent elevation of these moraines. At the north-eastern end of the moraines a number of flat-topped hills and ridges were of the same height, and all capped by several inches of a brownish deposit, which proved on examination to be a fungus similar to those found in the lakes at winter quarters. The whole district seems, therefore, to have been at quite a recent date a lake bed. The lake has been elevated and drained, and its bed has been dissected by streams, whilst * The evidence secured by Debenham suggests that this material also may have a local origin. 98 GLACIOLOGY the higher land which formerly existed to the east and constituted the boundary of the lake has been worn down and removed during the recent elevation of the moraines by a combination of the successive summer thaws and marine erosion. Thus in the case of all three of these moraines, those of the East Fork of the Ferrar Glacier, those of the Dry Valley, and the Stranded Moraines, the conclusion is irresistible that a considerable portion of the material composing them has either been brought many miles up the coast or has been carried right across the Sound. The three agencies which alone could be responsible for this transport to any large extent are: (1) Shore-drift. (2) A considerably greater extent of the ice-sheet and all its affluents, such as glaciers, barriers, &c. Of such an extension there are abundant evidences, of which we may here mention the finding of granitic and schistose erratics at a height of 1100 feet on the slopes of Erebus. (3) The third agency is the transporting power of icebergs and pieces broken off the ice-foot. At Cape Royds, especially around Flagstaff Point, large boulders of kenyte were fre- quently seen being carried out to sea on pieces of the ice-foot, and some of the icebergs were observed to contain much fine rock debris. This occurrence of kenyte boulders of some size as far north as Granite Harbour has already been noted. The probable explanation of their distribution will be con- sidered when the past history of the Great Ice Barrier is being reviewed. The Piedmont. The piedmont ice which has been traced continuously from the Drygalski Ice Barrier to New Harbour, a distance of 150 miles, narrows in very much south of New Harbour. Whereas to the north of this its width has been from 10 to 15 and even up to 20 miles, it is only 2 to 4 miles wide south of the Ferrar Glacier. This narrowing in width is no doubt connected with the presence of that great horst within a horst, the Royal Society Range. Before considering the remarkable ice slabs and Snow Valley to the east of the Royal Society Range we may refer to the piedmont south of the entrance to the Ferrar Glacier Valley known as the Butter Point Piedmont. This is part of the great fringe of glacier ice which borders the great coastal shelf of Victoria Land. It has its origin on the slopes of the Northern Foothills several hundred feet above sea-level,* and at Butter Point is about 24} miles wide. To the south it fringes the sea for 6 miles, and then takes a turn to the S.8.W. as the landward border of the Stranded Moraines, finally ending at the entrance to the Blue Glacier. To the north it continues for a dozen miles as a fringe to the foothills which form the southern border of the lower portion of the Ferrar Glacier Valley. A view of this piedmont looking westerly from McMurdo Sound is shown in Plate XXI. At the sea it is a cliff which varies in height from 6 to 20 feet, and during the early days of our stay at Butter Point this cliff was overhung by a fine snow-cornice. During the summer thaw a large number of very fine icicles were formed beneath * From about 1000 feet to about 1500 feet. PLATE XXI Frc. 1. THE BUTTER POINT PIEDMONT SOUTH OF THE ENTRANCE TO THE FERRAR GLACIER VALLEY | Zo face p. 98 a - i : e n : 7 ,: ss F ory 7 iv 7 i - a o a . BUTTER POINT PIEDMONT GLACIER 99 the overhanging edges of this cliff, and at one spot where the cliff was about 12 feet high these icicles grew until they reached the drifts on the sea ice and became 6 or more inches in thickness. The effect of the summer sun on the icicles was curious. When freshly formed they were quite clear and sound, and if they were broken in half no structure could be seen on the broken surfaces. After a day or two's ex- posure, however, to the direct rays of the sun they developed a radial fibrous structure, which was very marked and comparable with that of a belemnite. Ata further stage of their melting they became so rotten that icicles with a diameter of 3 or 4 inches would crush easily in the hand, having been reduced apparently to a mere shell. Remarkable examples of the plasticity of ice were to be seen along the ice-cliff in the early days of January. We have already mentioned that many of the icicles had grown until they had reached the snow-drifts on the sea ice below the cliff. As the thaw got in its work on the cornice from which these icicles depended large portions of it fell off, and many other portions gradually subsided. The icicles below the fallen portions were of course smashed to fragments, but many of those beneath the parts which subsided more slowly were bent into the most weird shapes imaginable. We have frequently seen icicles converted in less than twenty-four hours into snake-like shapes, or bent at right, and even at acute, angles without the slightest sign of fracture within the icicle itself. The place at which the bending took place merely became slightly flattened and widened, as does the bend in a glass rod. The surface of this piedmont was very rough. Near and parallel to the edge of the cliff at the place where our depot was placed were one or two cracks several inches wide. The ice was full of sediment, and in consequence of this the top 2 feet became very rotten indeed during our stay at the point. REVIEW OF THE PIEDMONT OF THE WEST COAST OF ROSS SEA* This piedmont is restricted to the low-lying part of the great horst, from the Blue Glacier, south of the Ferrar Glacier to the Drygalski Ice Barrier, a distance of 160 miles. It is hard to say exactly where the snow, creeping down the eastern slopes of the coastal hills, passes from the condition of hard snow into that of glacier ice, but on the assumption that the change takes place at the flattening of the foothills to the surface of the coastal plain, the width of the piedmont, where it attains its maximum development, that is, south of the Drygalski Ice Barrier, may be taken as about 20 miles. It narrows to about 10 miles east of Mount George Murray. * This has since been named the Wilson Piedmont in memory of Dr. E. A. Wilson, Chief of Scientific Staff of Captain Scott’s Last Expedition. 100 GLACIOLOGY This width is maintained until the Nordenskjéld Ice Tongue is approached, and there it almost ends near Charcot Bay and Cape Bruce. To the south side of the Nordenskjéld Ice Tongue it reappears, having there a width of from 7 to 8 miles, extending with slightly varymg width from here to New Harbour. Its surface area cannot be far short of about 1500 square miles. Its upper surface is for the most part convex from the foothills to the sea- cliff. It is rough and irregularly pitted. Probably dust blown off the ranges contributes to this end. In places, as between Mount Chetwynd and Mount Creak, it is seamed with channels apparently formed by thaw-water. (See Fig. 33.) They seem to be of different origin to the shearing channels already described as conspicuous features at the Drygalski Ice Barrier Tongue. Probably they are formed by thaw-water streams having their origin in the steep slopes of the plateau rocks above the foothills at the head of the piedmont. Seawards the piedmont terminates either in low cliffs, from 10 to 50 feet in height, or in a steep, convexly curved slope. The piedmont rests on a foundation which is certainly in part formed of solid rock. It is also certain that at intervals some morainic material of the nature of bottom moraine is present, but there is no evidence of its attaining any considerable thickness. Nothing of the nature of till (or boulder clay) was observed under the piedmont. At the same time it must be admitted that the deepest hollows below sea-level in which boulder clay would be most likely to accumulate are still hidden under the ice. The piedmont cannot be in a state of active movement, as no single instance was observed of its having ridged up the sea ice in contact with the base of its cliff, a result which would cer- tainly follow from rapid forward movement, as was observed in the case of the old sea ice at its junction with the southern side of the Drygalski Ice Barrier. In the vicinity of the outlet glaciers the piedmont of course merges insensibly into the ice of those glaciers. The question which now arises 1s, what is the origin of the piedmont ? Two suggestions may here be offered :— (1) That it is a shrinking remnant of the part of the old Ross Barrier where it was fed chiefly from the snows from the western plateau. (2) That it owes its origin (@) partly to local snowfall on the platform on which the piedmont rests, (b) partly to snow drifted (i) by plateau winds, (1) by the southerly blizzards. This second suggestion may be termed the snow-dune theory. In reference to the first suggestion, it is certain that the Ross Barrier has at one time covered the whole of the plain upon which the piedmont now rests from a little south of the Ferrar Glacier mouth to at least as far north as the Drygalski Glacier. When it is said that the ice of the Great Ice Barrier formerly covered the plain, on which the great piedmont of the west shore of Ross Sea rests, it is to be under- stood that the ice of this piedmont did not come necessarily from the south, but was THE WILSON PIEDMONT GLACIER 101 derived, in part at all events, from the huge outlet glaciers of the inland plateau west of Ross Sea. But this ice was certainly confluent with that of the Ross Barrier. An examination of the map (Plate III.) shows that the eastern portions of all the great glaciers entering Ross Sea along its west coast show a trend somewhat to the north of east as far as Cape Ivizar. Thus the East Fork of the Ferrar Glacier, the North Fork and Dry Valley, the Mawson Glacier, and the Davis Glacier all have an E.N.E. trend, whereas the trend of the coast-line is almost exactly north and south. It is suggested that this deflection towards the north is due to the shouldering action of the Ross Barrier with its powerful thrust from the south. In regard to the second theory, that the piedmont is formed partly of local snow which has fallen on the surface of the coastal plain, partly of snow drifted from the inland plateau across the ranges, it may be stated that there can be no doubt that vast quantities of snow are conveyed from inland seawards by the action of the plateau wind. Where the plateau wind blows straight down the gateways in the great horst formed by the outlet glaciers, such as the Ferrar, Mackay, and Mawson Glaciers, &c., it carries with it a continuous stream of snow crystals, the air being as thick as a hedge during blizzards on these glaciers, for four or five consecutive days on occasions. Such snow when it reaches thé coast is distributed far and wide over the surface of the sea ice. It was this somewhat thick covering of snow with its high sastrugi which prevented our taking the motor car more than about one-third of the way across McMurdo Sound towards the mouth of the Ferrar Glacier. In the late summer, when the sea ice has broken away from near the mouth of the glacier, any snow carried from inland down the glacier by the plateau wind is of course blown out to sea and quickly melts in the salt water. Where, however, the elongated tabular mountains of the great horst, with their steep, almost precipitous, eastern slopes form a lee to the westerly plateau wind, their snow-drifts must necessarily accumulate on a grand scale. Professor Hobbs has already suggested that much of the Antarctic ice along the shore-line of the continental mass is formed from drift snow. There can be little doubt that such is the case. During the few days that the Northern Party were at or near the Backstairs Passage Glacier it was noticed that when the plateau wind was blowing at times with blizzard force it carried dense masses of drift snow down this pass in the range. Vast quantities of this snow were swept out over the surface of the piedmont to the open sea about 15 miles distant, but a considerable amount of it must have lodged on the surface of this glacier. Whether or not any portion of the piedmont ice of to-day is actually the relic of the old ice mass, which was formerly an integral part of the Ross Barrier, is a question which cannot be proved, though it is by no means improbable that some of the ice is an actual survival of the former Ross Barrier sheet. It may be regarded as proved that a considerable portion of the nourishment of the piedmont glacier ice is received from blown snow, and the ice in some sense may therefore be considered a snow-dune ice. ) 102 GLACIOLOGY CAPE ROYDS, EREBUS, CAPE BARNE, TURK’S HEAD, GLACIER TONGUE, HUT POINT, AND MINNA BLUFF EVIDENCE Glacial conditions, past and present, were especially studied by us in the neigh- bourhood of our winter quarters at Cape Royds. The observations of Ferrar and Dr. E. A. Wilson had made us familiar with the fact that Ross Island shows evidence of two distinct types of glaciation. The first is the glaciation effected in former times by the Ross Barrier, when its surface stood fully 1000 feet above the present level of McMurdo Sound, and when its northern edge extended at least as far north as probably Cape Washington. Even at the present time the southern side of Ross Island, between Cape Armytage and Cape Crozier, is being subjected to glaciation by the northern edge of the Ross Barrier. That this glaciation is still active is evident from the immense crevasses and pressure ridges at the meeting-point of the Ross Barrier cliff and the rocks of Ross Island on Cape Crozier. The pressure ridges already figured by Scott and Ferrar near Pram Point also indicate active glaciation still in progress in that region. This glaciation of Ross Island, effected by the Ross Barrier, has left most interest- ing traces of the former presence of the ice sheet in the form of deeply trenched elon- gated rock basins, now occupied by lakes, as well as by magnificent terraces covered with blocks of granite, schist, gneiss, Beacon Sandstone, &c., transported as small to large boulders from the old land masses of the mainland to the south and west. During the maximum glaciation Ross Island must have stood out from the surface of the Ross Barrier as a huge nunatak. The flotsam and jetsam from this great ice flood has formed the remarkable terrace near the one thousand feet level. When one surveys the small rock basins, some scooped below sea-level, such as Sunk Lake, Deep Lake, &c., as well as the canal-like grooves cut in a meridional direction through the kenyte lava, one cannot but be impressed with the considerable erosive power of thick glacier ice, thrust forward by the enormous glaciers which fed it to the west and south. Secondly, there is evidence of a local glaciation still in progress. This is due to glaciers formed from snow precipitated on the surface of Ross Island, as well as to drift snow which has streamed over the surface of the Ross Barrier, and has then escaped seawards towards McMurdo Sound, over the long volcanic ridge which extends northwards from Cape Armytage to beyond Glacier Tongue, a distance of about 15 miles. One would, therefore, expect to find, at Ross Island, the glaciers most active where there is now the heaviest precipitation of new falling snow, as well as of drift snow derived from earlier falls. The parts of Ross Island nearest to Ross Sea and McMurdo Sound receive a small snowfall, at Cape Royds equal to perhaps about 7 inches of rain (rain never actually falls in this region, but the measurement of the snow is given in its equivalent of rain). As a matter of fact, Mount Bird and the coast-line from there to Cape Crozier is more or less buried PLATE XXII WO Fic. 1. GLACIER TONGUE, ROSS ISLAND ‘es 2” Fic. 2. WEST SIDE OF GLACIER TONGUE Showing snow cornice formed by southerly blizzards [T. W. Edgeworth David pare [ To face p: 102 GLACIER TONGUE 103 under glacier ice. The southern and south-western slopes of Erebus are also still being heavily glaciated, but the north-west slopes of Erebus are almost free from glacier ice.* Since the retreat of the Ross Barrier back to its present edge, to the south of Cape Armytage, the glaciers radiating from the south-west slopes of Erebus have invaded the vacated territory, cutting through the old marginal moraines of the Ross Barrier, and forming later moraines. These are built up partly of fragments of kenyte lava, partly out of redistributed material of the old marginal moraines of the Ross Barrier. We may commence with the most active glaciers examined by us, viz. those on the south-west slopes of Mount Erebus, extending as far south as Glacier Tongue. Glacier Tongue. Glacier Tongue is a very remarkable instance of a glacier jetty on a comparatively small scale. It is about 5 miles in length from east to west, and from a quarter to about three-quarters of a mile wide from north to south. Its surface is slightly convex, rising from its seaward end eastward to its point of attachment to the land. At the point where our depot for the southern journey was established on it, a little over 1 mile east of its western extremity, it was between 40 and 50 feet above sea-level at the highest points observed. The material of which it is formed is true, blue, glacier ice. This was found to be crevassed for at least 4 miles outwards from its point of attachment to the land. On its north side Glacier Tongue is levelled up by the drift snow carried by the south-easterly blizzards, this being of course the weather side of the Tongue. On its northern or leeward side the Tongue terminates in a low cliff, frequently with overhanging snow cornices. Its northern wall is deeply indented at intervals so as to form natural small docks, and advantage was taken of this by the Nimrod’s party. It was found possible to warp the ship close up to the cliff by ice anchors, and she could ride out the fiercest blizzard here in comparative safety. The accompanying illustrations show the appearance of this cliff late in February 1909. During the winter months this low cliff, for the most part, is completely masked by sloping drifts of snow; as summer thaw proceeds, and the ice breaks up, the foundation of sea ice under the drifts cracks up, and carries the overlying consoli- dated snow-drift out to sea, until eventually a low vertical cliff is left, as shown in the photograph. We thus see repeated on a smaller scale the same phenomena at Glacier Tongue as those already described at the Nordenskjéld Ice Barrier Tongue. The accompanying sketch after H. T. Ferrar (Fig. 44) shows the shape and situation of Glacier Tongue. Two questions of special interest suggest themselves in regard to Glacier Tongue. First, what is the source of supply of its ice ? Second, is it aground or afloat ? In regard to the first question, it may be stated that the width of the land at the * It was for this reason that that portion of the mountain was selected as the route for the ascent of March 1908. 104 GLACIOLOGY back of the glacier, measured in the direction of the trend of the glacier, is only 3 miles, and of this about 14 miles slopes down towards the Ross Barrier instead of towards Glacier Tongue. This eastern half of the land cannot therefore directly contribute much ice to nourish Glacier Tongue. How then can a mass of ice which projects 5 miles into the sea, and has a width on the average of about half a mile, and a thickness of from 400 to 800 feet, be nourished by a land surface only 14 miles in width ? The explanation of this remarkable phenomenon is probably to be found in the following geographical structure of the country in its vicinity: Glacier Tongue is to leeward of a comparatively low gap in a long peninsula. The southern end of EREBUS Inaccessible 1. 3 MS Murdo Sound STATUTE MULES GEOGRAPHICAL MILES Skelch Showing Glacier — ee lala Tongue Arrer-H-T Ferrar. Z Fic. 44 this peninsula is from 1000 feet to as much as 1300 feet above sea-level. In a northerly direction it gradually descends to a comparatively low gap opposite the point of attachment of Glacier Tongue, then the land ascends somewhat rapidly towards the summit of Mount Erebus, over 13,000 feet above the sea. Erebus of course offers an immense obstacle to the wind currents, and the blizzard wind which near Hut Point blows from about 8.8.E. is deflected, as shown by the trend of the sastrugi near Glacier Tongue from §.S.E. into a nearly east and west direction, consequently immense streams of snow-laden air flow over the south-western slopes of Mount Erebus as well as over the depression at the base of the long peninsula, terminating southwards in Hut Point, and contribute largely the necessary névé for the nourishment of Glacier Tongue. Some ice is also derived from the heavy snow- drifts which le on the south-west flanks of Erebus, adjacent to the shore end of the GLACIER TONGUE ; 105 Tongue. On this ‘theory Glacier Tongue is therefore chiefly formed of drift or dune snow. Another possible theory as to its mode of origin is that it is a shrinking remnant of a lobe of the old Ross Barrier which formerly overflowed the saddle to the east of Glacier Tongue. Such a lobe might have been deflected from east to west, just as are the modern blizzard winds by the resistant massif of Erebus directly opposed to its northward movement. In regard to the question as to whether Glacier Tongue is aground or afloat, it may be stated that on February 13, 1908, soundings were taken at a point a little over half a mile back from the west end of Glacier Tongue, which reached bottom at 1574 fathoms. The arming of the lead brought up a quantity of serpule and siliceous sponge spicules ; in fact, the bottom of the sea there must be as white as snow with the siliceous sponge spicules. Obviously we are confronted here on a smaller scale with a similar problem to that which has already been discussed in connection with the Drygalski Ice Barrier Tongue. The surface of Glacier Tongue nowhere exceeding about 40 feet above sea-level in this locality, the thickness of the ice cannot be greater than about 400 feet at this spot, whereas the depth of the sea is 945 feet. If this same depth was maintained right under the glacier, there should be a depth of 585 feet of sea water between the bottom of the glacier ice and the floor of the sea. As already stated, at about 3 miles back from this seaward end the surface of Glacier Tongue rises 70 to 80 feet above sea-level, and if the sea shallows slightly in an easterly direction towards the land, as is likely, the eastern portion of the glacier is probably aground. The chief question now is, is the western half of the glacier afloat or aground? Obviously the presence or absence of a well-marked tide crack should settle this question. Certainly a small, but not well-defined, tide crack was noticed by us on the northern side of Glacier Tongue. It was suggestive of a slight, though not strongly marked, differential movement between the sea ice and the glacier ice. One would have expected a more pronounced tidal crack had Glacier Tongue at this point been resting firmly upon the bedrock. When we were on the Nimrod, lying under the lee of Glacier Tongue, we tried to determine whether or not the glacier was rising and falling with the tide, as evidenced by the level of the ship’s rail in relation to the marginal cliff of the glacier and the position of the wave-worn groove with its icicles at the base of the glacier cliff in relation to sea- level. We were unable to notice any appreciable difference in level in either case during a rise and fall of the tide. We must therefore conclude provisionally that the western part of the Tongue is afloat.* * This view has subsequently been confirmed by Captain R. F. Scott’s British Antarctic Expedi- tion of 1910-13. Two miles in length of the seaward end of Glacier Tongue broke away during a blizzard on March 1, 1911, and was found later by T. Griffith Taylor’s party near Cape Bernacchi, at the entrance to the Ferrar Glacier Valley, about 50 miles to the W.N.W. 106 GLACIOLOGY The problem now presents itself as to how it is possible for a long, narrow, floating mass of ice—if it is floating, its seaward portion being only from one-quarter to half a mile wide—to resist the force of the blizzard winds and strong accompanying currents which in summer time, after the breaking up of the ice, sweep down McMurdo Sound. One would imagine that under these conditions Glacier Tongue would quickly break off at its seaward end, and float away as bergs. We find, on the contrary, that in the interval of between four and five years which had elapsed between the date of Captain Scott’s expedition in the Discovery and that of our visit, the length and breadth of the Tongue had been pretty uniformly maintained. It is quite possible that here, as is assumed to be the case at the Drygalski Ice Barrier Tongue, the Tongue has pushed out a bottom moraine, or submarine esker, like a great railway embankment, and is sustained rigidly on this for at least one- half, possibly for as much as three-quarters, of its length. It is still difficult to understand, even on this hypothesis, why the tip of the Tongue does not snap off and drift away. Many more soundings are needed on both sides of the glacier, and particularly on its seaward extremity, before this problem can be solved. Turk’s Head. About 6 miles north-westward of Glacier Tongue is the Turk’s Head Glacier. The steep slopes above the Turk’s Head Nunatak are heavily glaciated, and the glacier is strongly crevassed. It seems that here, and in the direction of Cape Barne farther north, the glaciation on the western slopes of Erebus attains its maximum. The probable cause for this, as has already been suggested, is to be found in the vast quantity of drift snow, which has swept on to this part of Erebus from the surface of the Ross Barrier to the south. Thus the gathering ground which supplies the ice for this glacier, for Glacier Tongue, and for the Cape Barne Glacier, may not be merely restricted to the western slopes of Erebus, but may be potentially a considerable surface of the Ross Barrier. A huge ice cave more than 50 feet in height is a conspicuous feature in this Turk’s Head Glacier. It is situated just at the point where the glacier descends from the rocky shore into the sea, and has doubtless been excavated by waves impelled by blizzard winds, at a time when there was open water to the south of the glacier. As shown in the accompanying photograph, the ice at this point is heavily crevassed. At the foot of the glacier was a large iceberg, so much crevassed that its top was a series of sharp pinnacles. There seems no reason to doubt that this berg had been recently broken off from the Turk’s Head Glacier, and it is very possible that two other bergs composed of glacier ice, seen stranded a little to the north of Turk’s Head, were derived from the same source. The ice in this glacier close to where it leaves the land must be about 150 feet in thickness. The view on Fig. 2 of Plate XXIII. shows how completely swathed in ice PLATE XXIII Fic. 1. TURK’S HEAD GLACIER Showing large wave-worn cave on side, facing southerly blizzards, at point where glacier reaches the shore Fic. 2, SMALL GLACIER Entering McMurdo Sound to south of Turk’s Head Glacier, looking north-east to Mount Erebus [To face p. 106 THE SKUARY 107 and névé the terraced slopes of Erebus are in this region, and illustrates another small glacier of the Norwegian type descending into McMurdo Sound. Very little rock is visible at all excepting close to the shore-line. Passing now about 2 miles farther to the north-west, one reaches the spot ealled by Captain Scott the Skuary.* The Skuary. The Skuary is an area of bare land abutting on the southern border of the Cape Barne Glacier, and some 6 or 7 miles south of our winter quarters at Cape Royds. The exposed land is about 24 square miles in extent, and is covered, except at the cliff faces along the shore, and some of the more im- portant and steeper of the hills and ridges, with a thick mantle of morainic material which, as far as could be judged in a cursory visit, seems to be mainly of local origin. Some small fragments of tuff were observed belonging to a variety occurring in situ at Turk’s Head; but there seems to be a total absence of the continental type of plutonic, hypabyssal, and sedimentary erratics with which Cape Royds is strewn. The evidence points to recent glaciation by a local Erebus glacier sub- sequent to the maximum extension of the continental ice sheet, and, in fact, the Skuary is still bounded on the side adjacent to Erebus by what is probably the shrunken remnant of this same glacier. The moraines consist almost entirely of a compact brownish kenyte, a type prevalent in the immediate neighbourhood. This kenyte is somewhat lighter in colour than that met with at Cape Royds. It is rendered porphyritic by light coloured and clear felspars, is most beautifully weathered, and the gravel which cover the depressions of the beds of the various little rills which drain the area are full of felspars, mostly cleavage fragments, but some of them were whole felspars with their edges distinctly rounded off as if by the action of running water. It is remarkable that all these felspars were chemi- eally so unaltered that they were almost transparent. They were mostly of a very light yellowish colour. Scattered about the Skuary are a number of small cones, consisting chiefly of angular fragments of brownish kenyte, with here and there a fragment of fairly fine-grained tuff. Along the margin of the glacier, where it bounds the rocky area, there is a somewhat regular row of from ten to twenty similar cones, separated from one another by a distance of only a few paces. Probably most of them are eskers exposed to view through the retreat of the glacier, but the presence of one undoubtedly intrusive parasitic cone makes one cautious in attributing the formation of all these cones to glacial action. When the Skuary was visited on November 18, 1908, the thaw had just set in in earnest. This particular day was cloudy, and the streams of thaw-water had consequently been frozen, but the ridged appearance of the snow-drifts, and the presence of ice in stream channels, all testified to the thawing influence of the sun’s heat during the past one or two days. On November 18th there was still a quantity of snow left, but the Western Party, when passing this spot at the * Captain Scott has more recently changed this name and substituted the name Cape Evans. 108 GLACIOLOGY beginning of December, remarked that scarcely any snow remained, in spite of the fact that wind laden with drift snow had been blowing for three or four days at the end of November. Cape Barne. Immediately to the north of the Skuary is the important Cape Barne Glacier. This is also fed by the snows which lodge on the south-western slopes of Erebus. It is about 24 to 3 miles in width, extends several miles inland, and terminates seawards in a magnificent ice-cliff. This measurement represents the whole width of the cliff face from the cape to the north to the Skuary to the south-east. The height of the cliff varies from about 50 feet to about 150 feet. Where highest, about 3 miles beyond Cape Barne, it has advanced as a tongue several hundred yards beyond the most westerly limit of the rest of the glacier cliff. A view of the highest part of this ice-cliff is shown on Plate XXIV. Fig. 2, with Cape Barne in the distance. The summit of Cape Barne is 300 feet above sea-level. Plate XXIV. Fig. 1 shows a general view of this cliff looking southwards from half-way between it and Cape Barne. A study of the sea ice at the base of the cliff did not show any evidence of pressure ridges having been developed through forward movement of the glacier mass. There was of course a well-marked tide crack, showing that the glacier was aground. It may be concluded that the ice of the Cape Barne Glacier, if in a state of movement, as is rendered probable by the presence of the crevasses, is moving so slowly as not to crumple up the sea ice in front of it. That movement, if any, is very slow is also proved by the fact that during the whole time Cape Barne Glacier was under our observation, from September 1908 until early in December, no large masses of ice were seen to break away from the cliff. Had there been much movement in the glacier, obviously the upper part of the cliff would soon have overhung its base, and under gravity large fragments would have become dislodged, and would have broken up the sea ice at the base of the ice-cliff. From Cape Barne, which bounds the Cape Barne Glacier on the north, to Horseshoe Bay, a total distance of about 4 miles, the coast was examined by us in some detail, the area being near to our winter quarters, and the geological map (Plate XCV.) was constructed by us from a plane table survey. From the Cape Barne Glacier to Horseshoe Bay the coast-line is mostly formed of bare kenyte lava. At our winter quarters at Cape Royds we were particularly for- tunate in having exposed to view a region intensely glaciated, which had formerly been buried to a depth of fully 1000 feet under the ice of the Ross Barrier. The region abounded in ice-eroded lake basins and tarns, as well as in large grooves, like small canals cut by the ice out of the kenyte lava. A typical groove is Shown in Fig. 1 of Plate XXYV. This canal-lke groove measures in width about 6 to 8 feet, in depth about 5 feet. The granite erratic in the photograph measures 4 feet by 3 feet by 2 feet. PLATE XXIV ‘j wy. Fie. 1. CAPE BARNE GLACIER Looking south-eastwards towards Cape Evans Fic. 2. ICE CLIFF AT WEST END OF CAPE BARNE GLACIER With Cape Barne in the distance. Cliff over 100 feet high (T. W. Edgeworth David [Zo face p. 108 ae a ed , are! — = - = — 4 7 7 : ~*~ i _ CAPE BARNE 109 The height above sea-level is about 200 feet. The surface of the kenyte, on account of the great absorption of heat by day and the rapid cooling at night, bringing about a quick disintegration of the rock through mechanical expansion and contraction, has lost nearly all its former glacial str7w through this frost weather- ing. Only in one instance were well-preserved grooves observed on the surface of a granite block, wedged into an angular hollow of the kenyte in such a way that it still retained the direction of the grooves produced by the great ice sheet when at its maximum. ‘The light colour of the granite has led to its being subjected to less extremes of temperature than the black kenyte, hence its surface is much better preserved. The way in which this boulder has become embedded in the kenyte and then hollowed out and grooved, is shown on the special map of this area. The direction of the grooves is from §. 25° E. to N. 25° W., true. The general trend of movement of the ice is also indicated by the bearing of the long axis of the glacial lakes. Thus the long axis of Terrace Lake trends about N. 30° W., that of Deep Lake and Sunk Lake trends about N. 15° W., Islet Lake about N. 35° W. The long axis of the largest of these lakes, Blue Lake, runs about N. 40° W., that of Clear Lake also N. 40° W. The trend of the main wide shallow valley, glacially excavated, that extends from Backdoor Bay to Horseshoe Bay, is about N. 10° W. It may be said generally that the trend of the glaciation on the whole appears to have been about between N. 10° W. and N.N.W. An interesting feature in the lake basins is Sunk Lake. As shown in the cross section from C to B,* the surface of the ice of Sunk Lake is 18 feet below sea-level, and the rock bottom of the lake probably 50 to 60 feet below sea-level. This lake is distant only 3 chains from the shore-line. While, as will appear later, there is abundant evidence for a recent uplift of the land in this region, there is no evidence of recent subsidence. The heavy downthrow fault which bounds Ross Sea on the west, with its displacement of the order of 7000 to 8000 feet, appear to have antedated the great glaciation. The fact that the bottom of this Sunk Lake rock basin is below sea-level seems good evidence for the hollowing capacity of glacier ice. Careful search was made by us over this intensely glaciated region of Cape Royds for any trace of true boulder clay, but we entirely failed to discover any. It must be remembered that the Cape Royds area was not by any means the lowest de- pression glaciated in this region by the Great Ice Barrier. As shown by the soundings of the Nemrod, at a point about 83 miles north by west from Cape Royds, and only 3 miles distant from the nearest land, McMurdo Sound is 459 fathoms (2754 feet) deep, whereas the ice at Cape Royds was 1000 feet thick a few miles to the north, and to the west it was about 3750 feet thick. Under these circumstances the bulk of the bottom moraine, possibly of the nature of boulder clay, would be submerged under McMurdo Sound, and the morainic material stranded near Cape * See Plate VIII. in section on Meteorology, and detailed map of the Cape Royds area, Plate XCV. P 110 GLACIOLOGY Royds would be chiefly of the nature of lateral moraine. Obviously the high level terraces shown on the map about 1} to 14 miles easterly from Cape Royds are of the nature of marginal moraine, marking the former level to which the ice flood reached up the slopes of Ross Island, at that time a gigantic nunatak. At the same time it seems strange that a mass of glacier ice 1000 feet thick, moving for centuries over nearly level rock surface like that in the vicinity of Cape Royds, did not produce, by crushing the kenyte rock to powder, a tough boulder clay. If fine comminuted rock material (rock flour) was originally produced here under the ice sheet it must have been washed subsequently to lower levels by sub-glacial thaw-water. All that is left at present, in the way of morainic material around Cape Royds, are thin and comparatively insignificant patches of small boulders intermixed with kenyte rubble. These are only of about a couple of acres in area, and not more than about 1 foot in thickness. Farther east, up the foothills of Erebus, are much more extensive elongated mounds and terraces, belonging to the old marginal moraine proper of the old Ross Barrier. The general appearance of these moraines is shown in the frontispiece to this volume. These terraces and mounds vary very much in thickness, from a few feet up to 50 or 80 feet. In connection with these moraines of the western slopes of Erebus, Ferrar quotes a statement by Dr. E. A. Wilson, that he observed near Cape Royds, during the period of summer thaw, streams of water emerging from underneath these moraines. Dr. Wilson concluded that probably there were still masses of glacier ice buried under the moraines.* A feature of these moraines which puzzled us very much was the appearance of what may be termed paths. These paths ran at various angles in relation to the slope, either vertically or obliquely. Some suggested that they were tracks left by seals crawling inland, others that they represented cracks due to irregular movements resulting from the thawing of underlying masses of ice withdrawing support from the overlying moraine; the whole settling under gravity may have developed irregular cracks which became channels for thaw-water, and thus the paths may have been formed.t+ The moraines, which were obviously of the nature of marginal moraines left by the great ice sheet, comprised a vast number of erratics, which have been de- scribed elsewhere, in the second volume, by Professor Woolnough. They comprise pegmatites, often containing garnet, aplite, syenite, sodalite-syenite with wohlerite, quartz-diorite, granophyric granite, porphyry, granophyre, felspar porphyry, minette, * It was observed by one of us (Priestley) that the uplifted marine shell-beds of the Cape Barne district rested on ancient ice, probably a relic from the maximum glaciation, 7 It may also be suggested that these “ paths” may be due to alternate expansion and contraction of the morainic material. From this point of view they may be of the nature of infilled contraction cracks, PLATE XXV Fic, 1. GRANITE ERRATIC 4 ft. x 3 ft. x 2 ft., lying in glacially eroded wide groove in Kenyte lava, High Hill, Cape Royds | David = eS 2 eae Ss PS Fic. 2. ERRATIC OF RED GRANITE NEAR BACKDOOR BAY, CAPE ROYDS | David | To face p- 110 CAPE ROYDS 111 vosgesite, porphyrite, diabase-porphyry, solvsbergite, sapphire-bearing trachyte, spherulitic trachyte, porphyritic basalt, actinolite-schist, tremolite-schist, phyllite, several varieties of red and grey granites, granulites with scapolite and pyroxene, and of course a plentiful admixture of kenyte and kenyte-tuffs. In places very coarse porphyritic gneisses are met with amongst these erratics. Sedimentary rocks had been collected from here in the form of fragments of Beacon Sandstone more or less converted into quartzite, quartzite perhaps older than the Beacon Sandstone, containing much titaniferous iron, fragments of saccharoidal marble, marble partly silicified, oolitic limestone partly replaced by quartz and much resembling the Cambrian Durness limestone of Scotland, as well as fragments of dark grey cherty rocks. These old moraines containing these considerable varieties of eruptive rocks, together with old sedimentary rocks, are in sharp contrast with the moraines derived from Erebus proper. The latter are almost exclusively formed of kenyte lava and tuff, with an occasional sprinkling of trachyte or basalt. In addition to these moraines forming terraces on the west slope of Erebus, uplifted beaches occur at intervals amongst the terraced moraines. These are described in detail under the heading of ‘‘raised beaches.” Foreign boulders occur, varying in size from a few inches up to 5 feet in diameter. The largest of these foreign boulders are formed of the red granite which is so abundant on the mainland. It will be noticed on the map of the Cape Royds district that these erratics of red granite have a linear direction as regards their present distribution, the trend of the line being about N. 30° W. The question may be asked, why did the Great Ice Barrier Glacier in McMurdo Sound, in the neighbourhood of Cape Royds, move in a direction west of north instead of due north, following the trend of the Sound, with possibly a slight set to the east of north due to the component of pressure from the great western glaciers of Victoria Land? The probable explanation is, that during the period of maximum glaciation the western slopes of Erebus, like its other portions, harboured large glaciers, which moved off down the slopes towards McMurdo Sound in a westerly direction ; the westerly component of pressure supplied by them was sufficient to slightly deflect the northward moving ice of McMurdo Sound in a westerly direction. (See Fig. 2 of Plate XXV.) A large erratic of kenyte on the south-east side of Pony Lake, near our winter quarters, measured 49 feet in circumference and 10} feet high. The dimensions of some of the granite erratics near Cape Royds are as follows :— 1. Red Granite, 6 feet 9 inches by 3 feet 4 inches by 2 feet. 2. Red Granite, 11 feet in diameter. 3. Grey Granite, 2 feet 6 inches by 2 feet by 1 foot 3 inches. 4. Aplite, 2 feet 6 inches by 3 feet by 1 foot 3 inches. That these moraines of foreign erratics extend for some distance to the west of 112 GLACIOLOGY Cape Royds is very probable, for in summer, when the sea ice and ice-foot had been swept away, one could see huge boulders of the granite submerged at some distance from the shore, their light colour making them easily distinguishable from the surrounding kenyte. The moraine terraces above Blue Lake appear to be made up principally of angular fragments of a dark, fine-grained volcanic rock, with phenocrysts of augite and olivine. Among these fragments were a good many hexagonal prisms of the same rock remarkably regular, some of them from 2 to 3 feet long. A number of blocks of tuff were also present. The commonest and largest blocks were a yellowish, fine-grained friable tuff. Along the eastern shore of Clear Lake it was noticeable that the only prominent erratics, other than basalt and kenyte, were a yellowish-green trachyte, which appears to have been the oldest of the Erebus series of eruptions. Fragments of diabase or quartz-dolerite, from the huge sills of that rock on the mainland, were of frequent occurrence. In regard to the moraines left by the glaciers from Erebus when, subsequent to the recession from McMurdo Sound of the former Ross Barrier, they were able to over-ride the ground which it formerly occupied, we observed in the southern portion of Blue Lake seven mounds of kenyte rubble. These we called eskers. The general shape and distribution is shown on Fig. 45. The eskers appear to be composed of fine kenyte rubble, and may have been deposited by sub-glacial streams from an old glacier formerly descending from Mount Erebus into the southern basin of the Blue Lake.* Passing northward from Cape Royds we reach Horseshoe Bay. Here, for the first time since leaving Cape Barne, the volcanic series of Mount Erebus disappears once more under a permanent cover of glacier ice. The latter is the piedmont glacier of Horseshoe Bay. ‘This glacier forms an ice-cliff on the eastern portion of Horseshoe Bay from 50 to 60 feet high. This is the terminal face of an almost inert mass of ice fed by the névé fields of the north-western slopes of Erebus. That the ice is not in active movement is proved by the general absence of crevasses, of which only small examples were observed. One of these had its sides fringed with beautiful feathery ice crystals, which had evidently grown from the moisture in the comparatively warm air coming up from the bottom of the crevasse. This moisture became deposited on projecting points of the crevasse walls. Another phase of growth of these secondary ice crystals produced hexagonal plates, sometimes as much as 7 inches in diameter, and comparable with those found on Murray’s dredging line. The latter crystals are illustrated in Fig. 1 of Plate XXVI._ Fig. 2 is a view across Horseshoe Bay looking towards Cape Bird. This piedmont glacier appears to be continuous as far as to Cape Bird. Near * We were unable to ascertain the nature of the foundation on which they rested. It may have been either rock or ice. ZL “d anf of | pred &q ogoyg | uosameyy ‘q Aq oj04q] parg edup spavaoy yyatou Suryqooy ‘spAoy odep jo yyAtoN spAoy adep ‘10qyva vas Jo qno ueyxvq odoa SutSpoap uo peutso,y AVA HOHSASUOH SSOUOV MATA *% ‘OM STVISAUO AOI ‘1 PM IAXX ALV Id . a —— ‘) 3 t - ‘° a a . a ee a 7 \ ‘3 = fe 4S oe = a J - a 7 sf - a= = - i - “>. . 2 | | . = oe | ae | . ah < =— Vy. = CAPE ROYDS 113 ESKERS on GRAVEL MOUNDS yN Scale | Chatn to an Inch. Brg Esker | 15 ¥d§ x10 Yas Ls 8 fF high Double Esker%. > 26 YS x7 fr Yds . 8/* high S| a \| g| 10 Y5+8 Yds el 7/2 Ft high & Double Esker LO VIS «39 VOUS 3 VAS x 3 Yds 3 Ft high SVISXS VIS 4F hgh ) 6 a5 «6 Yo (5tEsker 5 Ft high Fic. 45 114 GLACIOLOGY the farthest point north along the coast visited by us, just beyond Horseshoe Bay, we found several foreign erratics, including many pieces of undoubted Beacon Sandstone. We now pass on to Cape Bird. The photographs of Plate XXVII. show the general appearance of this cape near the point where Macintosh and McGillan landed previous to their sensational trip overland to Cape Royds. In picking up their depot and tent Mawson obtained a series of specimens of rocks from the shore-line. The dominant rock was later described by Jensen. These rocks were mostly erratics composed of trachytes, of strongly alkaline kulaites or trachy- doleritic rocks, sub-alkaline basalts and dolerites, some enstatite-bearing, some olivine-bearing. Erratics foreign to Ross Island were not observed. In the upper figure it will be noticed that there is a well-marked terrace, suggestive either of its being a raised beach or a parallel road. It is very similar to the feature observed along the east coast of Backdoor Bay, and appears to be a similar height above sea-level. The height of the Backdoor Bay terrace was about 50 feet. It will be seen that the glacier, mantling around the parasitic volcanic cone in Fig. 1, does not reach sea-level. In Fig. 2 a small parasitic cone is shown immediately over the boat. The absence of foreign erratics, as far as we could judge at Cape Bird, is probably to be explaimed by the slight westerly deflection imparted to the Ross Barrier by the pressure of the ice descending the west slopes of Erebus. This would of course tend to push the great marginal moraines of erraties, foreign to Ross Island, away to sea at some littlesdistance from the coast, before the Ross Barrier reached Cape Bird. Cape Bird proper is 25 miles distant, in a north by east direction, from Cape Royds. The spot from which Mawson collected the erraties described by Dr. Jensen was approximately 10 miles south by west from the cape, and almost opposite to Mount Bird. SUMMARY OF THE FERRAR GLACIER AND CAPE ROYDS REGION We are now in a position to review briefly the structure of the inland ice and glacier ice, past and present, between Scott’s farthest west, on his western journey, and the moraines of the western foothills of Erebus abounding in erratics foreign to Ross Island. The same features so conspicuous on the section from the South Magnetic Pole area to the Drygalski Ice Barrier Tongue are repeated. On the left and west is a high plateau, rock-free, and covered no doubt to a considerable depth by the inland ice sheet. Its level is singularly uniform, varying from a little over 7200 feet to about 7550 feet. This remarkable uniformity of level is maintained for no less a distance than 110 miles. Next, eastwards, one reaches the great horst. This rises at first in the Lashley Mountains to an altitude of 8590 feet; still farther east, in Mount Davis, to 9000 PLATE XXVII Fic. 1. GLACIER AND TERRACE NEAR CAPE BIRD The terrace may mark a former shore line Fic. 2. GENERAL VIEW OF THE COAST NEAR CAPE BIRD With parasitic voleanic cone in distance [To face p. 114 SUMMARY OF THE DISTRICT 115 feet, while in Mount Lister the horst culminates in a peak nearly 13,000 feet high. This peak is only an elevated horn on a plain, the level of which ranges from 11,000 up to nearly 13,000 feet. Towards the seaward ends of East Fork and Dry Valley there is a remarkably deep notch in the coast-line. This is known as New Harbour, and measures 10 miles wide by about 8 miles. One cannot but infer that this remarkable inlet is due to the prolonged excavating action of the two most energetic branches of the Ferrar Glacier, as it was when the ice flood was at its maximum, viz. East Fork and North Fork. The inlet is in every way comparable with that of Granite Harbour, but is on a somewhat larger scale. As already stated, the Dzs- covery Expedition obtained soundings of over 100 fathoms within a quarter of a mile of the coast of Granite Harbour, which suggest that this harbour is a deeply eroded glacial fiord. Unfortunately no soundings, as far as we are aware, have as yet been obtained at New Harbour. Unless the wide fiord has been largely filled in with moraine material by the retreating branches of the Ferrar Glacier, there can be little doubt that deep soundings should be obtained close inshore here, as at Granite Harbour. Soundings obtained by Captain F. P. Evans of the Nimrod show that to the north of Granite Harbour, at 6 to 8 miles from the land, the depth of the sea ranges from 360 fathoms up to 462 fathoms. His soundings between Cape Bird and Cape Royds show that there is a uniform depth of from 460 to 470 fathoms along the east side of McMurdo Sound at only 4 miles off the land. The few soundings which he obtained midway between Granite Harbour and Cape Bird prove the existence of a remarkable submarine ridge. The depth of water over this ranges from about 110 fathoms to 170 fathoms. Three possible explanations suggest themselves to account for this*submarine nage — 1. That it is a tectonic ridge due to the upward warping of the sunken segment. 2. The sunken segment between Ross Island and the mainland in this region may not have been warped, but may have been originally flat. The depth of 110 fathoms may represent the approximate amount to which this segment was depressed below sea-level originally, and the depth in excess of those met with in the soundings near Granite Harbour and along the west coast of Ross Island may be due to the increased erosive force of the McMurdo Sound portion of the Ross Barrier where it received the extra loads and pressures from the glaciers of the mainland on its west margin, and those of Mount Erebus on its eastern side. 3. It is possible that the maximum depth recorded, such as 472 fathoms near Cape Bird, approximately represents the depths to which the sunken segment of McMurdo Sound originally descended, and the shallower central portion may represent a vast amount of moraine material which has been transported on the Ross Barrier from the south carried from the direction of Minna Bluff, Mount Discovery, and Mount Morning, 116 GLACIOLOGY as well as from islands such as Brown Island and Black Island. Ferrar on his geological map of this region shows extensive moraines trending northward, from Black Island and Brown Island up to the edge of the “ pinnacle ice,” belonging to the Ross Barrier. A large portion of the surface of this pinnacle ice is heavily loaded with moraine material. During the thousands of years that the Ross Barrier was at or near its maximum, and flowing from the direction of Mount Discovery far to the north of McMurdo Sound, it must have transported a vast amount of moraine material north- wards, and dumped it on to the floor of the Sound. On this view the submarine ridge is largely a medial moraine derived from Minna Bluff and Black and Brown Islands. Possibly both 2 and 3 causes, as suggested, may have co-operated in producing this remarkable contour of the ocean floor. Beardmore Glacier. We can now leave Minna Bluff and discuss the glaciology of the continuation of the Antarctic Horst southerly to the Queen Alexandra Range where it is intersected by the Beardmore Glacier, and then trace this glacier to the inland ice, as far as Shackleton’s farthest south, in latitude 88° 23’, longitude 162° E. As already illustrated in the photographie album of the Discovery Expedition, the eastern slopes of the horst, as far south as the mouth of the Beardmore Glacier, show evidence of the presence of numerous outlet glaciers from the inland ice, and also afford clear proof that glaciation has recently been waning. This is well shown by the photographs, chiefly taken by Shackleton, as well as by the excellent sketches by Dr. E. A. Wilson. Shackleton’s photographs show very well that between the edge of the Barrier and the land trends a deep almost impassable chasm for a great distance. The origin of this is probably twofold :— 1. The rocks in contact with the Barrier Ice became highly heated in the rays of the sun, especially during the four months of perpetual sunlight, and consequently thawed the ice for a considerable depth where it has been in contact with the rocks. This is probably the chief cause of the existence of the gigantic moat which in most places bars access from the direction of Ice Barrier to the land. 2. In part the moat may be due to the Ross Barrier being actually forced or sheared away from the shore-line by great glaciers descending from the high plateau to the west to join the western edge of the Barrier. In this case the moat may be of the nature of a shearing plane like those already recorded in the case of the Drygalski Glacier. The chasm between land and barrier in Shackleton’s photo- graph (Plate CVII.)* undoubtedly illustrates a canal of the latter type. It is sug- gested in the description accompanying this plate that the chasm may be considered in part a tide crack “or line of constant rupture between the ice and the floating barrier, and that it was formerly attached to land along the shore.” There can be little doubt that it is quite analogous on a larger scale to Relief Inlet in the * The Voyage of the Discovery. SURFACE OF BARRIER 117 Drygalski Ice Barrier Tongue. In the work to which reference has just been made these structures are described as movement chasms. Their width is given as about three-quarters of a mile and their depth from 80 to 100 feet. It is probable that the inlets known as Skelton, Mulock, Barne, and Shackleton Inlets are all of the nature of outlet glaciers. The fact that both on the west and east sides of Ross Island vast quantities of boulders were discovered, up to heights of 1000 feet above sea-level, of granite and other rocks from the main- land is interesting proof of how, when the Ross Barrier stood about 800 feet above its present level, glaciers descending from the inlets just mentioned carried morainic material from the great horst in a general N.N.E. direction, the erraties probably crossing the long sill terminating in Minna Bluff, and then im- pinging on the western and eastern foothills of Ross Island. At the same time it is possible that these erratics were derived from granitic hills due south of Ross Island, such as those at the mouth of the Beardmore Glacier. The latter hypothesis is less probable than the former, as before the erratics had travelled the great distance of nearly 400 miles, which separates the Beardmore Glacier mouth from Cape Royds, they would probably have thawed their way down for some depth into the ice of the former Great Ice Barrier. Had they reached Cape Royds along this route they would probably have reached it as bottom moraine.* In his account in The Heart of the Antarctic, vol. ii. p. 12, Sir Ernest Shackle- ton states that the surface over which his party travelled over the Ross Barrier was continually changing. He noticed that at first there was a layer of soft snow on top of a hard crust, with more soft snow underneath that again. This pie-crust snow has already been commented on in the description of the Northern Journey. It is perhaps due to an actual melting of the snow just below the surface, when the general air temperature is below freezing, as well as to deposition of ice vapour ascending from a short distance beneath the snow surface. He states, ‘When the sun was hot the travelling would be much better, for the surface snow got near the melting-point and formed a slippery layer not easily broken.” Probably a certain amount of actual thawing, when the general air temperature was below freezing-point, had taken place in this instance, the thawing being due, as already explained in the account of the Northern Journey, to the low specific heat of ice. The quantity of soft snow met with on the Ross Barrier to the north of the Beardmore Glacier was no doubt due to streams of drift snow which are poured by the plateau winds out of the Beardmore Glacier Valley on to the surface of the Ross Barrier. Shackleton states that the surface of the Barrier near the land was broken up by pressure from the glaciers, but right alongside the mountains there was a smooth plain of glassy ice caused by the freezing of water that had run off the rocky slopes when they were warmed * They would also have become buried probably under some hundreds of feet of snow before they reached the edge of the Barrier. Q 118 GLACIOLOGY under the rays of the sun. “ This process had been proceeding on the snow slopes that we had to climb in order to reach the glacier. Here at the foot of the glacier there were pools of clear water around the rocks, and we were able to drink as much as we wanted, though the contact of the cold water with our cracked lips was painful.” At the time when this thaw-water was observed on the rocks at the edge of the Barrier, the temperature was ranging durmg the day from about 20° Fahr. at 8 A.M. to about 25° Fahr. at noon. The party that ascended Mount Erebus observed similar phenomena to that recorded by Shackleton, of a smooth plain of glassy ice at the foot of the steep rock slope of the old cone of Erebus at a height of over 6000 feet above the sea. At the time we believed this frozen lake to have resulted from the congealing of water from some hot spring, but it is far more likely that it was formed from thaw-water in summer draining off the dark rocky arétes, and forming a lake at the base of the steep slope. On the journey of the Southern Party over the surface of the Ross Barrier, Adams carefully noted the bearing from time to time of the chief sastrugi. These for the most part trended from 8S. or 8.S.E. to N. or N.N.W. In the case where the party were opposite one of the great inlet glaciers it was noted that the direction of the sastrugi at once changed, or a double set of sastrugi were present. The blizzard sastrugi still trended from a general south or south-easterly direction, whereas the sastrugi caused by the cold air comimg down from the plateau along the valleys of the outlet glaciers* had a trend parallel to that of these glacier valleys, that is, from a general westerly or south-westerly direction. In ascending the Beardmore Glacier it was found that all the chief sastrugi had their long axes parallel to the general trend of the valley. On the plateau, south of the farthest land seen, the sastrugi followed chiefly two directions. either between $.S.E. and S.E., or trending from due 8. to 8.S8.W. Their general trend is shown on map. These directions are shown on Plate VI. illustrating Chapter II. The glacier itself is about 100 miles in length, with a maximum width of about 25 miles. Its average width is about 12 miles. Shackleton observed that where the Beardmore Glacier junctions along the coast-line with the Ross Barrier it has raised enormous waves, by the force of its thrust, in the surface of the Barrier for fully 20 miles out from the shore-line. Again one is impressed here, as at the Reeves Glacier, with the stupendous erosive power of the glacier ice. This is shown on a grand scale in the beautiful photograph by Marshall, taken from the Barrier to south of Mount Hope (Plate XXVIII.), and also (Plate XXIX.) from the summit of Mount Hope looking up the Beardmore Glacier. One is at once struck by the sheer cut cliffs above “ Lower Glacier Depot ” on the right, where the dark shadow of the precipice bounding the glacier to the left is thrown across the surface of the glacier which recalls that of Mount Larsen. This cliff is approximately about 4000 feet in height. Next, one is impressed * That is, the true Féhn wind. PLATE XXVIII JUNCTION OF ROSS BARRIER With coast of mainland near Mount Hope, at entrance to the Beardmore Glacier. Mount Hope on left half of picture. The gap to right of centre a small side passage on the Beardmore Glacier. There is a strongly marked terrace, perhaps an old shore line, at the foot of Mount Hope [Photo by Eric Marshall [ To face p. 118 SIL “d aonf oz | [eysavyy orany “aqy Aq oyoyg | VYSTA eutea4x9 oy} UO eubaro ayy eaoqu ysul uses st (a0va.103 pooy oot 210) AVILA}. Q[V,, PAYAVUI-[[AM VW “SoLyVAde YYIM UMEAYS ST “qoay gerz ‘odoz_ qunoy,y ‘M'S'S ONIMOOT YUAIOVID HHUONGUVAT dN AdOH LNOOW AO dOL WOU MALIA XIXX HLV Id i U 7 7 7 ry P a 7 ' we 7 : % - 7 7 i 7 > ’ : : A - ea ee 7 oa 4 : 7 g - | a Laan 7 _ : _ BEARDMORE GLACIER Wag) by the remarkable ice-cut shelf to the right of Lower Glacier Depot, and to the extreme right of the photograph. This, on a larger scale, exactly recalls the similar structure noticed above the Mackay Glacier at Granite Harbour. It is evidence of valley in valley structure, or an over-deepened valley on a large scale. There can be little doubt that the Beardmore Glacier has formerly been so much higher than it is now, that it has completely overflowed the top of Mount Hope, burying it deep under ice. Mount Hope is about 2760 feet above sea-level, and its summit not only bears evidence of intense glaciation, but it is strewn with a variety of foreign erratics, including fragments of diabase and limestone. It is in itself a magnificent glacial ‘“ flood-gauge.” The stranding of these numerous erratics on its surface, all of which show evidence, when not recently weathered, of intense glaciation, has been due to the material being probably pushed up over the top of Mount Hope rather than dropped from above on to its surface during a retreat of the glacier ice. The glaciated foreign boulders, therefore, on Mount Hope are conclusive proof—no better could well be had—that the Beardmore Glacier here formerly stood 1800 feet above its present level. It must be remembered that this is a very conservative and quite a minimum estimate of the former thickness of the glacier ice. This makes the former occupation of the great shelf to the right of Lower Glacier Depot by the solid ice of the Beardmore Glacier not only probable, but reasonably certain. This cliff, then, may perhaps be looked upon as glacier-cut. Immediately below this shelf is evidence of a cirque. On the platform between the glacial-eut high level cliff and the great monolith of granite behind Lower Glacier Depot a small corrie glacier can be seen creeping down to join the Beardmore Glacier. The question here suggests itself, what was actually the approximate former thickness of the Beardmore Glacier when the ice flood was at its maximum? If one sees in a progressively deepened river valley high terraces of old gravel lying at, for instance, 1000 feet above the present bed of the river, and observes also that the river is now forming terraces at its present level, one obviously would not be justified in coming to the conclusion that the depth of the old river was formerly represented by the difference in level between its old gravel terrace and its modern one. One might argue in such a case that depth of water in the river was formerly 1000 feet. It may be the case with the Beardmore Glacier, as in the illustration of the river, that since the period of maximum glaciation it has materially deepened, that is, over-deepened, the original wide and comparatively shallow V-shaped valley. Since the diminution of snow supplies on the plateau the volume of the glacier has been much restricted, so that it has been unable to work over the whole of its old floor, confining its attention entirely to the low-lying portion of its present “ trogtal.” Again one is tempted to speculate as to whether the high level glacial terraces of the modern trogtal were originally excavated synchronously with the trogtal by glacier ice filling the main valley, or whether the 120 GLACIOLOGY large valley was excavated entirely first, and the smaller modern valley over- deepened in it later, or whether, in the third case, the modern trogtal and the “alb” terrace are being excavated simultaneously, the former by the ice of the main glacier stream, the latter by corrie glaciers. It appears to the authors that the cliff face above the corrie glacier is due to some more powerful erosive action than that of the well-known work of the cirque glacier at its sides and base, aided by changes of temperature and thaw phenomena. The foreign erratics on the top of Mount Hope force upon one the conclusion that thick masses of glacier ice have at one time attained to this level. It seems further probable that the level of this terrace was not the lowest level of the great glacier, the ancestor of the Beardmore, during the maximum of the ice flood. One may arrive at some approximation to the thickness of the Beardmore ice during maximum glaciation from the following consideration :— According to the levels taken by means of the hypsometer the ice surface of the Ross Barrier, near the outlet of the Beardmore Glacier, does not much exceed 200 feet above sea-level. This would give a thickness for the ice where it fanned out at a distance of some 20 miles from the shore of the Ross Barrier of from 1600 to 1800 feet. Opposite to Mount Hope itself the thickness of the ice is probably considerably greater. If we are correct in surmising that during the ice flood the ice was thick enough to flow steadily over the top of Mount Hope, it was probably at that time at least 3000 feet, certainly 2000 feet, higher than it is now.* One may, however, reasonably assume that during the maximum of the ice flood the ice of the Beardmore Glacier was from 3000 to 4000 feet in thickness, possibly more. Traces of waning glaciation were observed not only in the form of the foreign erratics stranded on the top of Mount Hope, but also in the shape of enormous lateral moraines. These moraines in the neighbourhood of the Cloudmaker ascended to 200 feet above the present glacial level, and evidently mark a very recent retreat of the glacier. Had the moraines been very ancient the blocks of stone would have crumbled down into the form of fine rubble as the result of the great diurnal range of temperature. An immense medial moraine was observed between the Cloudmaker and the great nunatak, Buckley Island, formed partly of coal-bearing rocks, partly of limestone. This moraine was traced over a distance of 60 miles up to the head of the glacier to the large nunataks of Mounts Bartlett, Buckley, and Darwin. It was in one of the sandstone blocks in this moraine, derived from the Beacon Sandstone, that a small piece of fossil wood, figured later in this volume, was obtained.t The boulders of the moraine here in December 1908 were * It does not of course follow that it was necessarily from 2000 to 3000 feet thicker than now, as one has to allow for perhaps a fair amount of glacial erosion subsequent to the climax of the ice flood. 7 The presence of small plant structures resembling rootlets in the adjacent shales suggests that the tree to which this wood, apparently coniferous, belongs was not drift wood, but grew in situ. PLATE XXX Fie. 1. LATERAL MORAINE ON WESTERN SIDE OF THE BEARDMORE GLACIER The hills on the left are of granite Fic. 2. THE CLOUDMAKER, 2500 FEET UP BEARDMORE GLACIER, HEIGHT, 9970 FEET [To face p. 120 ; ne * ABIOAIP AHUMGHAME AMERY PLATE XXXI PANORAMA, BEARDMORE GLACIER [To face p. 121 Xi PLATE XXXII 3s A My BEACON SANDSTONE COAL MEASURES (GONDWANA) OF MOUNT BUCKLEY A great nunatak at head of Beardmore Glacier. The steep slope of the glacier is obvious in the foreground | To face p. 121 BEARDMORE GLACIER 121 mostly melted into the ice, disappearing below the surface, but there was much fine yellowish rock dust on the surface of the ice. An examination of the photographs of the rocks in the neighbourhood of the Cloudmaker clearly suggest a much more intense glaciation here formerly than now. See Plate XXX. Fig. 2. A very interesting feature in connection with the north-west entrance to the Beardmore Glacier Valley at Mount Hope is the existence of a high shelf of rock intensely glaciated around the foot of Mount Hope facing the Barrier. Beautiful ice-cut facets can be observed on the left side, that is, the north-east side of Mount Hope. This part has received the double thrust of the Beardmore Glacier from the 8.8.W., and the Great Ice Barrier from the S.E. One would expect under these circumstances to see evidence, such as the photograph actually shows, of the most intense glaciation. Possibly the rock shelf represents a plane of marine erosion during the temporary submergence of the land in interglacial time. Subsequently the shore platform may have been uplifted and then glaciated. It will be noticed that over all the 380 miles from the Blue Glacier down to the Beardmore Glacier there is no trace of the remarkable coast platform piedmont conspicuous from the Blue Glacier northwards to Mount Nansen. The only suggestion so far of the existence of a coast platform is the rock shelf on the north side of Mount Hope. The fine panoramic view taken by Dr. Eric Marshall, seen on Plate XXXI., shows on the left the Dominion Range, which gradually slopes down to the extreme left towards the Mill Glacier. Next on the right are three well-marked nunataks, Mount Darwin (8023 feet), Mount Buckley (8384 feet), and Mount Bartlett (7869 feet). Mounts Buckley and Bartlett and the stratified formation at their base are formed of Beacon Sandstone, with seams of coal, laminated carbonaceous sandstone, and fireclay. These overlie a massive Cambrian limestone described later in this volume. It would obviously be a matter of very great interest to decide the elevation to which the névé fields have originally attained around these gigantic nunataks. The nunataks rise to a height of about 3000 feet above the ice at the head of the glacier. There can be little doubt that the high platform of coal-measure rocks, immedi- ately behind the two tents in the picture and below the top of Mount Buckley, has formerly been completely over-ridden by the ice, and it may be concluded that the ice was probably 1500 feet higher here formerly than it is at present. The stemming action exerted by the great nunatak just described against the flow of the inland ice northwards down the Beardmore Valley has led to the development of comparatively steep ice slopes near the nunatak. The nature of these ice slopes is well shown on Plate XXXII. The coal-measure rocks of the Buckley Nunatak rise to the left of the central figure in the illustration, and in the middle distance, just above the central figure, the long dark line may be observed of the medial moraine in which the fragment of fossil wood and coaly sandstone were found. The 122 GLACIOLOGY range of Beacon Sandstone, belonging to the nunatak on the left, is the one on which Wild observed the seven seams of coal, from one of which he obtained specimens by chopping them out with his ice axe. The Wild, Marshall, and Adams Mountains, rising respectively to heights of 11,217 feet, 10,494 feet, and 11,809 feet, afford fine examples of tributary glaciers and cirques, while farther north, beyond the Bingley Glacier, the mountains rise to 13,500 feet in Mount Dorman and 14,624 feet in Mount Kirkpatrick to the west of the Cloudmaker. The sharp peak near Adams Mountains affords a particularly fine example of rocky arétes. Ice-falls were encountered in farther ascent above the great nunatak, Mount Buckley, for over 50 miles farther to the south up to a level of about 8000 feet. The inland ice therefore, at least as far south as this in that locality, must be in a state of fairly rapid movement. At their farthest point south in lat. 88° 23’ S., long. 162° E., the Southern Party must have been at or close to the highest point of the inland ice at that spot, in fact at the “ice divide.” The terribly crevassed surface met with by Shackleton’s party on the Beardmore Glacier proves that the whole glacier must be in rapid movement, as of course is also evidenced by the vast pressure waves raised by this huge glacier at its confluence with the Ross Barrier and for 20 miles beyond. Huge as must be the annual output of ice from the glacier, it is only a small proportion of the former yield when the surface of the glacier was some 3000 feet higher than it is at present. Amongst other evidences of recent considerable shrinkage are the intensely glaciated terraces of rock, many hundreds of feet above the present level of the glacier. These are well shown on Plate XX XIX. The subject of the past history of the Beardmore and other outlet glaciers draining into Ross Sea, and there constituting the Ross Barrier, is so indisputably linked up with the history of the Ross Barrier itself, that we may now pass on to consider that most wonderful of all known floating piedmonts.* * The extent of the Barrier discovered by Lieutenant Filchner at the head of the Weddell Sea is not yet known, but it is improbable that it is as large as the Ross Barrier. PLATE XXNIIT 3000 FEET UP BEARDMORE GLACIER Cloudmaker in background to right. The glaciated rock terraces are foothills above the Cloudmaker To fuce p- 122 a) » - mn ’ 9 . : ; - ; 7 a S- _ J a _ 7 7 uy 7 > ‘s . os aa ’ i a - =i . [4 _ a i a a CHAPTER VI GLACIOLOGY (continued ) THE ROSS BARRIER THE Ross Barrier was formerly known as the Great Ice Barrier. In 1841 Sir James C. Ross sailed eastwards along the great cliff of the Ice Barrier for about 470 miles. In 1899 C. E. Borchgrevink followed the Barrier eastwards to Borchgrevink Inlet, near where Ross reported ‘“‘strong appearance of land.” In 1902 the late Captain R. F. Scott coasted along the Barrier for nearly 500 miles, penetrating beyond Ross’ farther pot east, and discovering King Edward VII. Land. He made a detailed survey of the Barrier edge, determining the height of the cliff at many points, and taking a number of soundings. He arrived at the important conclusion that the Barrier was afloat, except at its extreme east and west margins, and rises and falls with the tide like a gigantic landing-stage. His own observations from a . balloon, and those of Lieutenant A. B. Armitage in the course of a short sledge journey near the east extremity of the Barrier, revealed the important fact that the surface of the Barrier was not there uniformly level, but undulating. Scott says : *— “South of the rising slope ahead of the ship I had expected to see a continuous level plain, but, to my surprise, found that the plain continued in a series of long undulations running approximately east and west, or parallel to the Barrier edge: the first two undulations could be distinctly seen, each wave occupying a space of two or three miles, but, beyond that, the existence of further waves was only indicated by alternate light and shadow, growing fainter in the distance.” Scott further says that Armitage reported that, in his short sledge journey ot about 12 miles, he crossed four of these undulations. They extended in a general east and west direction, and were not in the nature of symmetrical anticlines and synclines. They presented rather the appearance of a peneplain dissected by broad mature valleys. The general depth of the latter was about 120 feet. Later, Lieutenant Royds, of the same expedition, made a sledge journey over the Barrier, from Hut Point to the south of Mount Erebus, in a general south-east direction, reaching the meridian of 176° E. near latitude 79° 33’ 8. Scott describes the surface over which Royds travelled as an unutterably wearisome plain, a surface * The Voyage of Discovery, vol. i. p. 148, London, 1905. 123 ~ tang : ek. “ee Barrier at maximum glaciation 80 50 Heights in feet SCALE 1: 6000000 \O_mls __80 mls - ,160 mls SOUTH POLE. io) Fic. 46.—Map of Ross Barrier showing glacier ribs, position of edge of Barrier in Ross’ time, 1841-42, and probable minimum extension of Barrier northwards, during the maximum glaciation. Amundsen’s discoveries are added THE ROSS BARRIER 125 such as he describes in his own southern journey. Scott's conclusion that the greater part of the Barrier is afloat, is based on the following considerations :— 1. When his ship, the Discovery, was lying alongside the Barrier in Balloon Bight,* its rail was about level with the Barrier surface there, so that he was in an excellent position to judge of any differential vertical movement between the ship and the Barrier. Although there was evidence of a considerable tide, ship and Barrier rose and fell regularly together. 2. The soundings, taken by him along the Barrier face, proved that the water was too deep to admit of the material of which the Barrier is formed resting on the bottom. For example: at a point at the base of the Barrier cliff, 115 miles E.S.E. of Cape Crozier, he found a depth of 455 fathoms. The adjacent cliff was only 60 feet high. 3. His survey of the Barrier showed that, in places, masses of ice, as much as 35 to 40 miles in width, had gone out to sea since the edge of the Barrier was charted by Sir James C. Ross in 1841-2. Scott’s numerous soundings in 300 fathoms were consequently made at spots many miles to the south of where the northern margin of the Barrier was situated in Ross’ time. The observations made by the Discovery Expedition also show that, where the Barrier is constricted, as between White Island and Cape Armytage, it is thrown into a series of undulations, implying a continuous thrust from a southerly direction. Scott also records (Voyage of Discovery, vol. ii. p. 312) vast disturbances in the surface of the Barrier off the eastern slope of Mount Terror: “ Here the sheet is pressing up and shearing past the land ice, raising numerous huge parallel pressure- ridges.” A fine illustration of this is published in the above work, large edition, vol. i. p. 303. On his first Southern journey Scott encountered heavy undulations in the surface of the Barrier opposite Shackleton Inlet, and Lieutenant M. Barne, of the same ex- pedition, met similar heavy undulations and disturbances in the Barrier surface opposite Barne Inlet. Speaking of Barne Inlet, Scott states (op. czt., vol. 11. p. 221): “It seems evident that the whole of this area is immensely disturbed, and it is doubtful whether a sledge-party could ever cross it, unless they were prepared to spend many weeks in the attempt.” Barne’s sledge journey also proved the im- portant fact that Scott’s Depot A, near Minna Bluff, had moved no less than 608 yards in 13$ months. This showed that the whole of the Barrier in this region was obviously in movement. Scott gives the direction in which it is travelling as a little to the east of north. 4. Scott states (op. cit., p. 312) that Lieutenant C. W. R. Royds took some serial temperatures in a crevasse extending from the north end of White Island near Mount Erebus. ‘Close to the land, he found that the temperature fell with the * This is now merged into the Bay of Whales, as discovered by our expedition, the spot where Amundsen wintered in 1911, before his famous journey to the South Pole. R 126 GLACIOLOGY depth to a mean of -9° (F.); but, at a distance of 10 miles from the land, he got a different result. Here, at first, the temperature fell, but as the thermometer was lowered its column rose again until, at a depth of 19 fathoms, it showed zero. Deeper than this he could not go, on account of the snow in the crevasse; but I Sed gee ROSS SEA “ ¢ 4 ——, je oe la a ee ea Bb ih feet. s ( / 150 * Pree PTL Py] ee TP ae be es wi f ms ria ’ SI i * # y Bf V ie 85 feet. i | H } ys v ‘ ! mS & f \ SS ! NS i H z ‘ a Ne o/ i Sa ao i \ Pa : ore oN 7 SS. rhs ' S Ne i . ‘é 1 yy NG ‘ is Las \ ‘\ 4“ : e X BAY / OF J ae Se ax ( ae a a A = Se sraest y/ 36 }) pacrotas.s ed — AB ye eae 2 Arurdee, = Late, WHALES a : _ Seale of Statute miles. / Wa ee 7 oe poy Senet Rg Ss / ae eo | FRAMHEIM I, | _ tease eno! 2 axaehieppbiaeesoategevet une iceere ee B Pressure fee Z | Feb? 2-49. Reeciin 3 y vel ; \ 3 \ of Barrer -Amundsen. \a\ Z o \*e\ Ve \ = 3 Ross x \ BARRIER SURFACE \ Fic. 47. Plan showing changes in the edge of the Ross Barrier near Amundsen’s headquarters at the Bay of Whales since the time of Scott’s Expedition in the Discovery in 1902. the Bay of Whales in 1911 is after Amundsen think it must be conceded that the only reasonable cause for such a rise of tem- perature as was observed, is the presence of water beneath the ice.” 9 2am The outline of The Shackleton Expedition, in 1908, skirted the Barrier eastwards, hoping to reach King Edward VII. Land, or, failing that, determined to winter at Balloon THE ROSS BARRIER 127 Bight. On arriving at the spot where Balloon Bight was formerly situated, we found that it had entirely disappeared ; an immense strip of the Barrier had evidently broken away and put out to sea since the time of Scott’s visit. The Nimrod reached lat. 78° 41’ S., long. 164° 30’ W., z.e. about 10 miles south of the latitude of the Discovery when at her farthest south in Balloon Bight in 1902. No bottom was found by us at 300 fathoms at lat. 78° 19’ S., long. 162° 53’ W. The approximate shape and extent of the mass of the Barrier which had drifted out to sea between 1902 and January 1908 is shown on the accompanying figure, the present general outline being taken from Amundsen’s plan in his work The South Pole, vol. i. p. 350. Obviously, it would have been impossible for such a huge mass of the Barrier to have gone out to sea in such a comparatively short time unless it had been afloat. Our discovery of land masses covered by ice, immediately to the south of the Bay of Whales (formerly in part Borchgrevink Inlet), suggests that the east and west valleys in the Barrier, in this region, may be due to the stemming action of the land in resisting the northward movement of the Barrier. This land, immediately to the south of the winter quarters, ‘“‘ Framheim,” of Amundsen’s Expedition, is shown on his plan as an island or nunatak, completely buried under ice, and 1100 feet above sea-level. In regard to disturbances indicating movement of the Barrier, Shackleton records that the long voleanie promontory, about 66 miles south of Mount Erebus, known as Minna Bluff, gives rise to heavy crevasses in the Barrier. He describes the surface there as “all hillocks and chasms, the pits often over 100 feet deep.” Macintosh and Day, of our expedition, when engaged with Joyce and Marston in laying a depot for the returning Southern Party, at the beginning of 1909, observed that the Barrier surface on the south side—the stoss-seite—was raised by the pressure of the ice farther south, apparently more than a hundred feet higher than the Barrier surface on the north—that is, the lee-seite—of the bluff. The appearance, as roughly sketched by Day, is shown on Plate XXXIV. This depot-laying party were so fortunate as to sight, on February 15, 1909, the bamboo pole, with its tattered flag, marking the old Depot “A” of the Discovery Expedition. This depot was established on October 1, 1902. It was about 9°2 statute miles from Minna Bluff,* in line with a sharp volcanic peak at the end of the Bluff and Mount Discovery. Thus 6 years and 6 months had elapsed since its : erection and the re-alignment of its position by Macintosh. It was found that, in the interval, it had travelled for a total distance of about 3200 yards, that is, 1 mile 1440 yards (2927 metres). The direction of the movement was towards about N. 30° E. This givesa rate of about 492 yards (450 metres) per year, or 1°348 * The original position of Scott’s Depot “A” is taken from the plan published in the Meteoro- logical Report, part 1, of the Nat. Antarctic Expedition of 1901-4. aaHIYuva SSOU AHL HO LNAWHAOW HO ALVY GNV NOILORUIG DNILVULSATII NVId ‘DoE S/ 3907 PAWNSSP UDIZELIEN I1qaUBEW "YOU! UP 07 72a4 000) 2/22G 1821749f *Ue/O Jo 7eY2 22IM2 aJOIG /E2UOZIIOH YING BuUIW JO apIS UsayINOG 24? buijUNOW JalIJeg SSOY ay7 40 a2! ay? buimoys uejd 40°g —") aul) uO u0172aS > ay ‘GI Ga4 ° ‘2061 '1'720 s : F , WILY: 17 ayy’ SO - Gf 70099 SUOJA)¥I. 5 yusluyuva P] ssouw 9718S - 397 .29/8S- SSIS, (+) 606)°S1'924 V 30dag $3302 si ol "SaiqaWO|!y 40 aje2g Ge vis “2 “SajlIW je21yde1BoaD 40 2182S *6061'S1 924 PUP 20611990 U2amjaQ 4al44eg 3d) 7219 ay? 40 JUaWAAOW — Buimous ueig — 7224 05) ay bia So cowae Wy SSoy 1oDvIg d L 9? Ye NY Cala | ns O/ *$a1}AWO}!y 40 aJe3g a 00! ° AIXXX WLV1d THE ROSS BARRIER 129 yards (1'263 metres) per day. The direction of movement of the Ross Barrier is also shown in Plate XXXIV. The important question may be discussed here, does this movement of the Ross Barrier, so conclusively proved at Minna Bluff, and in the great pressure ridges and shear planes near Cape Crozier, extend also to the eastern end of the Ross Barrier? Amundsen has shown that at his winter quarters, ‘‘ Framheim,” in the Bay of Whales, movement of the ice is practically negligible. The fact must here be borne in mind that ‘Framheim” is just to the lee of a large island completely smothered in ice, which appears to have stemmed back all movement in the immediate neighbourhood of Amundsen’s winter quarters. Nevertheless the following facts show that some movement is still taking place on the eastern side of the Barrier :— (1) High pressure ridges were encountered by Amundsen on the surface of the Barrier (a) at about 46 miles south of “ Framheim.”* These were evidently due to thrust of the Barrier ice against the southern and south-eastern sides of the ice-covered island south of ‘Framheim.” That the ice in this region is still in a state of movement, however small, is clear from the description given by Lieutenant Prestrud.+ He relates how, on November 8, 1911, at a point on the Ross Barrier about 20 miles southerly from ‘“ Framheim,” ‘there was a report about once in 2 minutes, not exactly loud, but still there it was. It sounded just as if there was a whole battery of small guns in action down in the depths below us.” This was in the neighbourhood of some small hummocks, no doubt indicating pressure near shearing planes. At and to the south of lat. 81° S. Amundsen records broken surfaces on the Ross Barrier, with strong pressure ridges. ‘‘ They extended as far as the eye could see, running north-east to south-west in ridges and peaks.” In the map illustrating Amundsen’s lecture to the Royal Geographical Society a slight indication of land is shown in the neighbourhood of these pressure ridges. The existence of an island hereabouts, though conjectural, is highly probable. About 40 miles farther east Amundsen shows high-pressure ridges lying off the land discovered by him between 81° and 83° S., just east of the meridian of 160° W., and probably continuous with Carmen Land. It may perhaps be significant that the trend of the pressure ridges on Amundsen’s line of march near 81° 8. is from south-west to north-east. This may be due to the strongest thrust coming from the great outlet glaciers, which transect the high ranges on the south-west side of the Ross Barrier. In regard to the Barrier south of Minna Bluff, Shackleton says (op. cit., vol. 1. p- 299) that near lat. 82° 38’ S. they encountered long undulations, “the width from crest to crest being about 1} miles, and the rise about 1 in 100. The depth of * The South Pole, Amundsen, vol. i. pp. 256-7; also zbzd., vol. ii. pp. 6-12. 7 Lbid., vol. 11. pp. 218-19, pp. 23-24, and especially pp. 170-72. 130 GLACIOLOGY these wide shallow troughs would thus be approximately 40 feet.” Jbid., p. 301: “The undulations run about east by south and west by north, and are at the moment a puzzle to us. I cannot think that the feeding of the glaciers from the adjacent mountains has anything to do with their existence. . . .” This observation was made near lat. 82° 51’S. Reference to the map of the Ross Ice Barrier shows that these undulations commenced at a point about 50 miles E.S.E. of the entrance to Shackleton Inlet, and about 60 miles N.N.E. of the lower end of the Beardmore Glacier. Later, December 2nd, near lat. 83° 23’ §S., Shackleton speaks of the undulations being very pronounced, consisting of ‘ enormous pressure-ridges, heavily crevassed and running a long way east, with not the slightest chance of our being able to get southing that way any longer on the Barrier.” Obviously these last violent disturbances are directly due to the pressure of the great Beardmore Glacier which forms so important an outlet for the inland névé fields. Shape and Height of the Barrier Ice Cliff. For information on this subject we are chiefly indebted to observations made by the Discovery Expedition of 1901-4, and to Ross’ observations in 1841-2. There are also a few observations near the Bay of Whales by C. E. Borchgrevink, as well as by our own expedition when cruising between Western Inlet and a short distance to the east of the Bay of Whales in January 1908. The headland of Western Inlet in the middle of the above photograph is over 100 feet high. At the head of Western Inlet, behind the above headland, the height of the Barrier cliff is only 20 feet. Thus the inlet, which trends nearly east to west, is evidently situated on a trough in the surfaces of the Barrier. Fig. 2 of Plate XXXV. shows another low portion of the Barrier at the farthest point east, along the Barrier face, reached by the Nimrod on January 24, 1908, in lat. 78° 41’8., long. 164° 30’ W. On the other hand, in the next photograph is a view of a lofty slice about to detach itself from the Barrier about 200 feet above sea-level. We named this slice “‘The Dreadnought.” It lay to the west of the Bay of Whales. According to the heights obtained by Captain Scott, the height of the Barrier cliff varies from 20 feet to 240 feet, and, according to the fewer measurements taken by us, from 20 feet to 200 feet.* As regards outline, reference to the map (Fig. 46) shows that the Barrier in Ross’ time projected northwards in a well-marked lobe between the meridians of 165° and 169° W. The sharp western boundary of this lobe was formed by a sheer cliff trending N.N.W. and §8.S.E., while to the east it was bounded by a deep indent. These two features appear to repeat themselves to-day, re- * According to Commander E. R. G. R. Evans, R.N., now in command of the late Captain Scott’s Expedition, no spot higher than 150 feet was seen by them when the Terra Nova visited the region early in 1911. PLATE XXXV Fic. 1. WESTERN INLET IN THE ROSS BARRIER Looking south with ice-blink to right. The headland of Western Inlet is about 100 feet in height. Near the head of the inlet the Barrier Cliff is only 20 to 50 feet high | Photo by David Fic. 2, SMALL INLET IN ROSS BARRIER To the east of the Bay of Whales. ‘The ice-cliff, at this inlet, comes down within 20 feet of the level of the sea [Zo face p- 130 , 7 . : 4 '. - 7 - - - a a he so - » - = ns * — ay i > oa) Oe ie PLATE XXXVI THE DREADNOUGHT An ice promontory about 200 feet high on the cliff face of the Ross Barrier [Photo by Wild [Zo face p. 130 PLATE XXXVII Fic. 1. EDGE OF ROSS BARRIER About four miles south of Hut Point. March 1, 1909 Fic. 2. CLIFF OF ROSS BARRIER Between long. 165° to 175° W. Height about 150 feet | David | Zo face p. 131 THE ROSS BARRIER 131 spectively in Western Inlet and the Bay of Whales. It will be noticed that the Barrier between the Bay of Whales and Western Inlet is higher than its general altitude between Western Inlet, on the meridian of 169° W., and the meridian of 175° E. This large lobe is probably due to the glacier ice coming from glaciers like the Devil’s Glacier, Axel Heiberg Glacier, Liv’s Glacier, possibly also the Beardmore Glacier, combined with the ice derived from Carmen Land and the areas between the latter and King Edward VII. Land. The ancestor of the Bay of Whales, like its modern descendant, originated, no doubt, in the stemming action of the high ice-covered island to the south of Amundsen’s winter quarters at Framheim. Possibly the lobe was nourished almost entirely by glacier ice coming from between Carmen Land and King Edward VII. Land, as well as by drift and new falling snow on the actual surface of the Barrier. Possibly Western Inlet owes its origin to the stemming action of some other, as yet undiscovered, ice-covered island to the south. The fact that since Ross’ time this eastern lobe has retreated no less than 50 miles southwards, shows probably that the ice supplies, on this eastern side of the Barrier, have diminished to an even greater extent than the supplies to its western side. The absence of high ranges in the direction of King Edward VII. Land and the land farther to its south accounts, no doubt, for the comparative calm of the weather in this region, as well as for its consequent low precipitation. Some observations may now be given on the internal structure of the material of the Barrier. Plate XXXVII. Fig. 1 shows the appearance of the northern edge of the Barrier, about 2 miles south of Cape Armytage, on March 1, 1909. The material here appeared to be entirely formed of well stratified old drift snow. It probably rested on a foundation of old sea ice of certainly more than one winter's growth. It was doubtful whether it should be considered as the edge of the Barrier proper. On the short sledge expedition by Shackleton, Armitage, and one of us, it was noticed that there was a gradual slope, about 8 feet high, where the sea ice joined the Barrier, and, between this spot and Pram Point, there was strong evidence of pressure ridges on the Barrier surface. It is usually very difficult to determine the exact limit northwards of the edge of the Barrier proper at this part of MeMurdo Sound, as heavy snow-drifts, formed by the blizzards, tend to build up ? an “apron” of hard snow over the sea ice lying to the north of the Barrier edge. It is probable that the Nimrod, in the position shown in the photograph, was still within the area of this snow and sea ice apron. The cliff of Ross Barrier, between long. 165° to 170° W., shown on Plate XXX VIL. Fig. 2, has a height of about 150 feet. This is near about half-way between long. 170° W. and the Bay of Whales. The cliff here was higher than the crow’s nest of the Nimrod, and was probably about 150 feet above sea-level. The photo- eraph shows that the cliff is composed, apparently down to the water's edge, of 132 GLACIOLOGY horizontally stratified layers of snow, no doubt now largely converted into ice. There is an entire absence of the vertical lamination and disturbed bedding with which one is familiar in true glacial ice in temperate latitudes. At the same time the fact must not be overlooked that in many of the Antarctic glaciers the ice, at all events in its upper portion, shows signs only of horizontal stratification. On the left-hand side of the photograph it will be noticed that the material exhibits a very perfect flat conchoidal fracture. Another proof that, though it may be ice in its lower portions, it is not formed of glacier ice is afforded by the entire absence of vertical fluting of the cliff face. Had even a small amount of rock dust been present in the material, as is usually the case in the land glaciers of Antarctica, this would quickly have formed dust wells when warmed by the sun’s beams, and these wells would have been enlarged downwards to form grooves, as we observed to be the case with the vertical faces of true icebergs facing the sun, 7.e. facing north. That the Barrier is not altogether formed of old compressed snow is, of course, obvious from the fact that great glaciers like the Beardmore, the Heiberg, the Devil’s Glacier, &c., are continually discharging into it vast volumes of glacier ice. It is also proved by direct observation. H. ‘I. Ferrar states:* “The intimate structure of piedmont ice shows that, as far as water-level, it consists of normal glacial ice. On the surface away from the land only fine snow was met with, but close to the shore crevasses and pressure ridges show massive and vesicular ice. The vesicular ice contains air amounting on the average to about 8°5 per cent. of its own volume, and the ice grains are usually less than } inch across.” One of us (R. E. Priestley) has recently observed that the material of the Barrier, in the cliffs at the Bay of Whales, is formed of true ice. This locality is, of course, in the immediate neighbourhood of the island buried under ice to the south of Framheim. The next piece of evidence, though it is not certain that it bears directly upon the question of the origin of the Barrier, is, in itself, very significant. Towards the end of the summer, early in 1908, two tabular bergs drifted from the north down McMurdo Sound, and grounded half-way between our winter quarters at Cape Royds and Cape Barne. During the winter, when the sea was firmly crusted over with ice, we visited these bergs, and were able to examine their internal structure by studying the walls of the wave-worn caves. They appeared to be wholly formed of compressed snow down to sea-level, with a veneer of sea ice in such parts as were exposed to the wash of the waves and the dash of the spray. During the summer of 1908-9 the Nimrod made use of one of these bergs as an anchorage for shelter from the blizzards. Soundings alongside the bergs, obtained by Captain F. P. Evans, showed a depth of 13 fathoms, 7.e. the berg was stranded in water having a depth of 78 feet. The berg rose to almost the same height out of the water, but as its eastern side had been lowered considerably through the tunnelling action of the waves and the collapse of * National Expedition, 1901-4, Natural History, vol. i., Geology, London, 1907, pp. 67-68. PLATE XXXVIII SOUNDING ROUND A STRANDED BERG In order to see whether the ship could lie there THE “ NIMROD” MOORED TO THE STRANDED BERG About a mile from the winter quarters. The “ Nimrod” sheltered in the lee of this berg during blizzards [To face p. 138 PLATE XXXIX SCOTT DEPOT “A” Rediscovered by Shackleton’s depot-laying party, Feb. 15, 1909. Depot originally left by Seott on Oct. 1, 1902 | Zo face p. 133 THE ROSS BARRIER 133 the snow roofs of the tunnels, approximately two-thirds of the volume of this berg was below water, one-third above. Obviously, therefore, the berg from the water- line to its base must have been composed of material far less dense than typical glacier ice. Some further light on the intimate structure of the Barrier is thrown by the section obtained by Messrs. Macintosh, Day, Joyce, and Marston at the site of Scott’s Depot “A.” Having re-located this old depot and re-aligned it, the party dug down in order to find what depth of snow had been deposited on the depot during the 6} years that had elapsed since its erection. They came upon the original snow surface on which the depot was formed at a depth of 8 feet 2 inches (2:5 metres). In order to determine the density of this snow they melted down a considerable quantity of it, and measured the volume of the thaw-water resulting. This showed that the annual accumulation of snow on this part of the Ross Barrier is about 15 inches (380 millimetres) of dense snow, almost névé, equal to about 74 inches (190 millimetres) of rain. This depot is in the latitude of Minna Bluff about 78° 40'S. Before proceeding to consider the probable origin of the Barrier, it is necessary to glance at its past history. Throughout almost all the Antarctic regions yet explored, there is abundant evidence of a recent and prolonged shrinkage of the ice masses and névé fields. The Ross Ice Barrier is no exception to this rule. Captain Scott's survey on the Discovery shows the position of the Barrier edge as he found it in 1902, and on his chart he gives the position of the Barrier edge as originally outlined by Ross as the result of the explorations conducted on the Erebus and Terror in 1841-2. These two outlines are shown on the map at the beginning of this chapter (Fig. 46), and prove that the face of the Ross Barrier has retreated southwards no less than about 45 miles from 1842 to 1902 at its eastern end. The mean amount of retreat during the above sixty years aggregates perhaps about 20 miles along the whole front of the Barrier. So much for horizontal shrinkage. The following facts refer to vertical shrinkage. The Discovery Expedition proved, from the evidence of stranded moraines 800 feet above sea-level, near Cape Crozier, that the surface of the Barrier at its western end has recently decreased in altitude by about 700 feet. Our observations at Cape Royds, upon the western slopes of Mount Erebus, showed that large lateral moraines, crowded with blocks of granite and other crystalline rocks, transported from the mainland to the south, were continuous for considerable distances at altitudes of at least 1000 feet above sea-level. It may therefore be concluded that, in late geological time, in the neighbourhood of Ross Island and McMurdo Sound, the Barrier has shrunk, vertically, by no less an amount than about 900 feet. At the time of maximum glaciation, there is also evidence that the outlet glaciers from the inland ice, such as the Ferrar Glacier—which formerly fed the Barrier—and the Beardmore Glacier s 134 GLACIOLOGY —which still feeds it—have shrunk vertically, the former by 4000 feet, the latter by at least 2000 feet. The shrinkage definitely proved at Mount Erebus may be taken to apply, more or less, to the whole of the Barrier surface. At the time, then, of maximum glaciation, if the sea-level was in its present position, the height of the Barrier at Cape Royds would have been 1000 feet above sea-level, and at Cape Crozier fully 800 feet. The average depth of the soundings along the present face of the Barrier from Cape Crozier eastwards is about 350 fathoms, or 2100 feet—z.e. in water of this depth, one-third of the Barrier material would have been above the water and two-thirds submerged. If it be assumed that the Barrier during maximum glaciation averaged 500 feet above sea-level instead of about 100 feet as at present, then in water of an average depth of about 2000 feet, one- fifth of the ice would have been above sea-level and four-fifths would have been submerged, on the assumption that the density of this ice as compared with the density of the adjacent sea water was not less than 8 tol. Thus it may be concluded that, by far the greater part of the Barrier during the maximum glaciation being ice, this Barrier ice must have rested and pressed heavily on the floor of Ross Sea. This would still be the case even if it be assumed that sea-level, during the maximum glaciation, was 200 feet higher than it is now, and even if the maximum depth as yet sounded along the Barrier be taken instead of the mean depth. The maximum depth recorded is 460 fathoms. If, therefore, during the maximum glaciation and submergence the Barrier surface at this deepest sounding to the east of Mount Erebus were 800 feet above sea-level, as much as a little over a quarter of the Barrier mass would be above sea-level, an amount quite sufficient to keep the Barrier resting on the bottom, even in this deepest part. In considering now the origin of the Barrier, two reasonable alternatives suggest themselves. First, the hypothesis put forward by Captain Scott—that the present Barrier is a direct descendant of the old Barrier formed during maximum glaciation, and that when, as the result of diminishing snow supplies, the old Barrier shrunk in thickness as it retreated Polewards, the weight of ice was no longer sufficient to keep the Barrier on the bottom of Ross Sea, and consequently the Barrier floated up off the sea bottom into its present position. Here it is still nourished by the smaller, but still active, glaciers of to-day. Scott, of course, would concede that drift snow contributes to even up its surface, but apparently does not regard this snow as an important contributing factor. The other alternative, to which we incline, is that there may not necessarily be any of the ice or snow in the present Barrier which belonged originally to the old Barrier during the maximum glaciation. The material of the Barrier at its sides is undoubtedly glacier ice. These ice-streams, when they reach the south-western shores of Ross Sea, fan out, the fans coalescing at their margins. Had there never been a maximum glaciation, each individual glacier might have formed a long ice-jetty projecting into the upper end of Ross Sea now occupied by the Barrier, much in the same way as do the present glaciers of THE ROSS BARRIER 135 Robertson’s Bay. During the maximum glaciation the coalesced ice streams formed a vast piedmont aground, just as, at the same epoch, did the Drygalski, Reeves, Campbell, Corner, and Priestley Glaciers of the Drygalski-Reeves Piedmont. Then, as the glaciers shrunk with diminution of the snow supplies, the piedmont floated up and retreated southwards, as Scott has supposed. Meanwhile the surface of this floating piedmont would form a receptacle like a vast shovel, or fork with much widened prongs, for snow falling on its surface, or drifted off the high plateaux which bound the Barrier region on the south-west, and the lower plateaux on the south-east from King Edward VII. Land to Carmen Land. Little by little, as the glacier ice towards the central and northern portions of the Ross Barrier became melted off from beneath, névé, passing into ice at a depth, would gradually take its place. This névé would result from the accumulation of superficial snow deposits. The observations of Macintosh and Day show that the snow which actually falls, or is drifted, on to the Barrier surface, must be an important contributor to its volume. A great deal of the Barrier extends southwards from its terminal face on Ross Sea, for a distance of fully 300 miles (483 kilometres), and even over 500 miles (805 kilometres) in the case of the Devil’s Glacier. The Beardmore Glacier, for example, at its lower end, where it joins the Barrier, is 350 miles (563 kilometres) distant from the Barrier face. It may be assumed that the annual amount of compressed snow contributed to the western portion of the Barrier surface, as the result of additions from drift snow as well as from actual precipitation, is about 1 foot (3048 metre). From the observations of Scott and Macintosh of the rate of movement of the Barrier near Minna Bluff, it may be inferred that the Barrier is travelling seawards at the rate of about 492 yards (450 metres) per year. From this one may argue that snow falling on the foot of the Beardmore Glacier, 350 miles inland, would take 1252 years to reach the edge of the Barrier where bergs dis- charge into the sea. At this rate, if 1 foot of snow™* is added to the Barrier every year, ice from the Beardmore Glacier, which left the foothills about 1250 years ago, if it reaches the Barrier cliffs at the present day, will be covered by a thickness of about 1250 feet of snow, without allowing for the compression of the lower layers into ice. Obviously, this theory gives a considerable thickness of snow to form the seaward end of the Ross Barrier. That the under part of the Barrier, except, perhaps, near its centre, is still formed of glacier ice, is suggested as being possible by the nature of its cross-section from east to west. This section is based almost entirely on the soundings and altitudes given by the British National Antarctic Expedition of 1901-4 along the face of the Ross Barrier. Reference to this section and to the plan of the Barrier shows that the * This estimate of an annual addition of 1 foot (3048 metre) of hard compressed snow, equal to about 7-5 inches (19 metre) to the Barrier surface, applies only to the Minna Bluff region, as far as the very limited observations up to the present extend, and is not necessarily of wide application. 136 GLACIOLOGY altitude of the Barrier is greatest, and consequently the Barrier ice is thickest, in the direct line of movement of the Barrier ice from the direction of Barne Inlet past Minna Bluff. As already shown by Day’s sketch, the Barrier ice, as it approaches the huge resistant mole of Minna Bluff, becomes thrust upwards for a considerable height on the southern slopes of the Bluff, so that on this thrust-side the ice is much higher than it is on the lee (the northern) side of the Bluff. The ice thus thickened on the southern slopes of Minna Bluff is shouldered away by the Bluff, until, as already stated, it takes up a path in a direction about N. 30° E. A continuation of this trend would carry it eventually to the vicinity of the highest part of the Barrier as yet observed, viz. 240 feet.* It will be noticed that the deepest sounding does not exactly coincide with the present path of the thickest Barrier ice, but when the volume of the ice from the south-western mountains was very much greater than it is at present, the larger ice stream may have been more weer TRE GWFF RIB THE EASTERN ICE RIBS. EAST oe 0 240 » co) i) 5 60 0 wo aw www wo oO OD a 45 Cd ‘300 tw 1000 feet cet | Ce a eos as or Present thickmess of Ross Ramer ice an assumoton of density of ie a6 Compared with that of sea water being 8 to! Vertical Sale Fathoms oy po Metres Increased thickness ~ “ . = = re = - "815 tol rad 1004 fag — 00 woo Further incraased thickness . : * . ” . < “Stol FOO) }aa0 S00 Approsimata former leve! of Barner Ice during the maximum glacebon A this time the whole of the Ica of the former Ross Barrier must have been resting on the sea floor 240 Height above Sea. tevel in feet 500. 460 Depth in Lathoms md Fie. 48. SECTION ACROSS ROSS BARRIER, EAST TO WEST, THE SOUNDINGS AND ALTITUDES AFTER CAPTAIN R. F. SCOTT deflected eastwards than the present ice stream, so as to have completely filled the deepest area sounded by Scott along the Barrier face, 460 fathoms, 75 miles E.S.E. of Cape Crozier.¢ The cross-section of the Barrier suggests that its structure is very similar to that of the Drygalski-Reeves Piedmont. Just as in the latter case one * We are informed that later measurements taken in detail by Commander E. R. G. R. Evans, C.B., R.N., of the British Antarctic Expedition of 1910-13, when surveying the Barrier cliff in Captain Scott’s ship, the Terra Nova, show that at present no part of the Barrier cliff exceeds a height of 150 feet. Probably, therefore, the above height of 240 feet is somewhat exaggerated, or it may be the case as the Barrier surface, in many places, has strong undulations trending east and west, the original measurement may have been taken on a cliff cutting the arch of an undulation, and the later on one cutting a trough. The first supposition is the more probable. + An alternative hypothesis is that the sea bottom under this thickest part of the Barrier has been raised by the thawing out of englacial moraine at the base of the ice sheet by the deep, relatively warm, layer of sea water, as has already been suggested in the case of the Drygalski Glacier. THE ROSS BARRIER 137 ean trace distinctly the individual ice ribs, belonging respectively to the Reeves Glacier, the Larsen Glacier, and the David Glacier,* so in the case of the Ross Barrier one can probably recognise the traces of ‘“‘the Bluff rib” derived from the stemmed and deflected ice of the Barne Inlet and other glaciers, from the mountains to the south-west of the Ross Barrier as well as the eastern ice ribs, perhaps derived from the coalescence of the Beardmore Glacier ice with that of glaciers farther to the south-east and east. While it is thus assumed that the higher parts of the Barrier represent fanned-out glacier ribs, the low-lying parts of the Ross Barrier ean be explained in at least three, possibly four, ways, as follows :— First, they may be due to the fans, or ribs, of the respective piedmonts afloat, contributing to form the Barrier, becoming very thin at their edges, as a consequence of prolonged spreading and consequent thinning of the ice as it progressively fans out wider and wider as it advances seawards. Secondly, these low areas may mark more or less radial strips along the Barrier where the edges of individual floating glacier fans fall short of each other, and so fail to coalesce, the stretches of sea between becoming built over with bay ice, lasting for many seasons, its surface receiving annual additions of drift or new- falling snow. This is obviously the case with much of the Drygalski-Reeves Piedmont. Thirdly, the low parts alternating with high may be due, and no doubt are in part due, to the existence of considerable undulations in the surface of the Barrier, particularly in the neighbourhood of the Bay of Whales and the Western Inlet. As already stated, Scott recorded that near Balloon Bight these long and wide undulations, trending nearly east and west, had a depth of 120 feet. As the greatest height of the Barrier cliff is usually about 150 feet, it is obvious that, if by the breaking away of bergs from the Barrier face the bottom of one of these troughs were exposed to view, the height of the cliff wall there would not exceed about 30 feet. The existence of Western Inlet in the Barrier 100 miles west of the Bay of Whales is, perhaps, to be explained as the result of differential marine erosion of a corrugated ice sheet, the sea eating back the thinner ice of the troughs more quickly than the thicker ice of the flat-topped ridges. Fourthly, it is by no means improbable that there is differential etching of the under surface of the Ross Barrier through the solvent action of water coming upwards from a depth, the temperature of such water being slightly in excess of that of the general temperature of the surface water. Reference has already been made to the influence of shoals in deflecting upwards these relatively warmer waters, and so keeping pools of sea water open, almost all the winter, on the lee side of such shoals in regard to the prevalent ocean currents. Comment has already been made on Ross’ discovery of warmer water at a depth in Ross Sea, and this conclusion has been abundantly confirmed by subsequent scientific expeditions. There can be no * To these must now be added the Campbell, Priestley, and Corner Glaciers. 138 GLACIOLOGY doubt as the result of our observations that the sea ice in summer is corroded by warm water from beneath, and that even in winter, where there is any obstacle on the sea floor which causes an upward deflection of the deeper waters, there the surface temperature of sea water is kept so high that sea ice cannot form. Under these circumstances, there can be no doubt that differential erosion must be a factor in determining the differential heights of the ice-cliff of the Ross Barrier, but that it is probably not an important factor, as is suggested by the fact that where the water of Ross Sea along the Barrier edge is particularly deep (over 400 fathoms), so that conditions would be unfavourable for upward currents, there the Barrier ice is specially thin. There can be little doubt that the thinness of the ice in the central section of the Barrier ice-cliff is chiefly due to the fact that this is just the portion which is farther removed from the sources of ice supply, the great glaciers of the horst and the smaller glaciers of Carmen Land and other lands bounding the Barrier on the east. SUMMARY The Ross Barrier is now, for the most part, a floating piedmont, the shrunken remnant of a much vaster piedmont aground. Its surface shows both radial and tangential undulations. The gently swelling radial thickenings of the Barrier represent the prolongations, for hundreds of miles seaward from the shore-line, of the great land glaciers, widely fanned out where they leave the land and plunge into the sea. The tangential or concentric undulations, having mostly an approximate east to west trend, represent pressure ridges chiefly normal to the paths of the main glacier streams which constitute the radial ribs. Partly these undulations repre- sent those great pressure ridges which start from the point where the land glaciers meet the Barrier surface, and, as the whole Barrier slowly moves seawards, become gradually transferred to the edge of the Barrier facing Ross Sea. Partly they represent pressure ridges, due to the stemming action of rocky islands smothered under the ice, like the one discovered by Amundsen to the south of Framheim. Such low-lying areas of the Barrier as have a radial trend owe the relative thinness of the ice, of which they are formed, (a) either to the glacier ice ribs becoming thin through fanning at their ends and at their sides, where they become welded together along their planes of contact, or (b) to the fact that these adjacent floating piedmont glaciers, failing to touch one another at their sides, never- theless become linked up by old sea ice, which, being protected from erosion by the glacier ribs or ice jetties on either side, accumulate as “bay” ice from year to year, until it acquires a considerable thickness. This thickness is constantly increased by additions of snow, whether derived by drifting from old falls, or originating in snow new fallen in situ. This process appears to be taking place at the present time at the Drygalski-Reeves Piedmont, which is such an important THE ROSS BARRIER 139 key to the structure of the Ross Barrier, but at the same time, as much of it is covered by moraines, it may be nearly all fanned-out glacier ice. The Ross Barrier is thus formed literally of “ thick-ribbed” ice with transverse pressure ridges. It may be compared to a shield formed of a wicker-work frame covered with hide, in which the rods represent the glacier ice jetties, and the smaller osiers the pressure ridges, while the drift and fallen snow represent the hide. The exact relation between the amount of ice that is being annually added to the Barrier from its great marginal glaciers, as well as from the drift snow and new- fallen snow on the Barrier surface, to what is lost by ablation, is not yet known. Near Minna Bluff the surface of the Barrier was added to at the rate of about 15 inches (380 millimetres) of dense snow, almost névé, equal to 7} inches (190 millimetres) of rain annually. At the same time, the evidence already given, in the chapter entitled Meteoro- logical Notes, makes it clear that on the whole, in the western portion at any rate, of Ross Island ablation is in excess of precipitation, as is suggested in particular by the evidence of Sunk Lake, where the surface of the lake ice, only about 60 yards (55 metres) distant from the sea, is actually 18 feet (5°48 metres) below sea-level. It is also to be noted that no information is at present available as to the rate at which the base of the Barrier ice sheet is being melted in the water of Ross Sea. That the amount of ice annually lost by melting must be very considerable is obyious from the following consideration :—Evidence shows that the sea ice of Ross Sea, which in a single season attains a thickness of about 7 feet (2°13 metres), is about half melted away during the summer, the melting taking place from below upwards: thus late in January the sea ice, formed during the preceding winter, is found to be full of corrosion hollows. Some of these hollows undoubtedly have been formed by the seals, which have bitten away the ice to form their breathing holes. Abandoned later by the seals, these old breathing holes become roofed over with young ice. But the number of these is negligible as compared with the millions of corrosion hollows which honeycomb the sea ice of Ross Sea late in summer. It would appear that near lat. 77° 8., at least 1 metre of ice is annually lost by melting. Evidence, already quoted earlier (in last part of chapter on Physiography, deal- ing with Ross Sea), shows that some of the deeper water of Ross Sea must be warm enough to melt sea ice, and therefore, of course, land ice also. This suggests the important consideration that as the result of relatively warm currents flowing south- wards under the eastern and central parts of the Ross Barrier melting may be going on there continually during the winter as well as the summer, and an appreciable thickness of ice is probably annually removed from the base of the Barrier through this cause. It would be of great interest and importance to ascertain what this amount is. An approximation might be made by experimenting with blocks of ice, which might be used as “ edge as Western Inlet and Bay of Whales. control specimens,” at such sheltered spots on the Barrier 140 GLACIOLOGY A number of these ice blocks could be sunk at intervals at such localities by means of an iron weight suspended below the block, and well msulated from it by a short piece of asbestos rope. The ice blocks could be suspended by steel piano wire, again insulated from the ice blocks by a short piece of asbestos rope, and the upper end of the piano wire could be attached to the base of the Barrier ice-cliff in one of the inlets, or preferably to old bay ice in a secure and sheltered spot in these inlets. An approximate estimate of the cross-sections of the ice streams of the western side of the Ross Sea region from just south of the Beardmore Glacier to the Reeves Glacier at Mount Nansen may be made as follows :— Of the Coastal Mountains shown on the section, the total length of which is about 750 miles, about 113 miles are occupied by well-developed glaciers, and of this width no less than nearly 100 miles is made up of outlet glaciers. These widths have been based on the following approximate measurements :— Width in Miles. 15 ; ‘ ; Beardmore Glacier. Uf : : : Glacier between Capes Lyttleton and Goldie (*), 10 : : Y Glacier of Shackleton Inlet. 12 : ; : Glacier of Barne Inlet. 10 : , : Glacier of Mulock Inlet. 8 : 5 : Glacier of Skelton Inlet. 6 Koettlitz Glacier. 2 Blue Glacier (*). 3 Ferrar Glacier. 4 Mackay Glacier. 2 Penck Glacier (*). D Fry Glacier. 5 Mawson Glacier. 3 Harbord Glacier. 4 Davis Glacier. 6 David Glacier. 2 Larsen Glacier. 12 Reeves Glacier. 113 miles. Glaciers marked thus (*) are “ Alpine” or ‘“‘ Norwegian” types of glaciers. The rest are outlet glaciers. It is possible that in the case of the glaciers entering the “inlets” in the above list the width of the inlet may be greater than that of the glacier which fills it with ice. The margin of error for the estimated widths of all the glaciers is considerable. For example, instead of 113 miles, their total width may not aggregate more than about 97 miles. It is assumed in the calculations which follow that the approxi- mate total width of such of these glaciers as are termed outlet glaciers is about 100 miles. If the exact cross-section of the ends of these glaciers were known, as well as their average speed of movement throughout the year, one would be in a position DISCHARGE OF ICE FROM VICTORIA LAND 141 to estimate the quantity of ice which they annually discharge on to the western side of the Ross Barrier and into the western side of Ross Sea. As regards the cross-section of the lower ends of the glaciers, the only data as yet available—and they are very meagre—are for the Drygalski Ice Tongue. This, as shown on our sections, has a mean thickness, in its central portion, of about 2000 feet. It is possible that its thickness at its centre, at a point 20 miles east of the shore-line, may even approximate to 3000 feet, as the central parts of this glacier are about 300 feet above sea-level. One may estimate that these glaciers may average 2000 feet thick for an aggregate width of fully 100 miles. As has been previously stated, we saw evidence that the whole mass was in movement from the fact that during a single night (December 17, 1908), in about 10 to 12 hours, one of the vertical shear planes near its northern edge moved about 14 feet. If this rate were maintained, it would mean a movement of about 3 feet (‘914 metre) per diem. If to this central mass of ice, 10 miles wide, the wedge-shaped portions of the ice on either side, each 5 miles wide, be added, the total cross-section of this glacier, where fanned out into the piedmont, would be about 15 miles (24 kilometres) by 2000 feet (610 metres). This would give a daily discharge of ice in the middle of December, when the rate is probably approaching a maximum, of about 475 millions of cubic feet per diem (13,486,264 cubic metres). If this average thickness of 2000 feet be maintained throughout the whole of the 100 miles in width of glaciers, from the Beardmore to the Reeves Glaciers inclusive, the total daily discharge of ice would be less than 3166 millions of cubic feet, and even if one-third of this amount be deducted to allow for thinning of the glaciers towards their sides, the amount would still have the enormous total of, in round numbers, over 2,000,000,000 cubic feet daily. At least one-half of this is probably annually added to the west side of the Ross Barrier, the other half being discharged into the Ross Sea, along its western shore. Thus annually from the Beardmore Glacier to Skelton Inlet, inclusive, the Ross Barrier may receive daily, from the outlet glaciers alone, an amount of ice equal to 1,000,000,000 cubic feet during the middle of December.* It may be interesting to compare this result with the known rate of movement of the Ross Barrier, and the amount of ice that is there daily pushed forward to the Barrier cliff face, where it breaks off to form bergs. * As regards other rates of movement of the glaciers of the Antarctic horst, Ferrar states (Nat. Ant. Ex., 1901-4, Geology, pp. 82-83), that at the south arm of the Ferrar Glacier the rate of movement is probably less than 6 feet (1828-77 millimetres) a month, while the Blue Glacier moves less than 4 feet a year. Both these glaciers are exceptionally stagnant, and are not a fair criterion of the rate of movement of the great glaciers like the Beardmore, the Drygalski, the Reeves, &c., which shear and ridge the sea ice or Barrier ice, and push the whole Ross Barrier in places some distance away from the land. This supposition has quite recently been confirmed by the observations of Griffith Taylor and Debenham of Scott’s last expedition, that from the middle of December to about the middle of January (1911-1912) the Mackay Glacier moved at the rate of about a yard a day. T 142 GLACIOLOGY The main rate of movement of the Barrier past Minna Bluff has been ascertained to be about 492 yards (450 metres) a year.* Reference to the cross-section of the Ross Barrier, already given on Fig. 48, shows that for its total width of 450 statute miles (724 kilometres) the Ross Barrier has an average thickness of about 720 feet. This would give a superficies for the Ross Barrier vertical cliff face of (in round numbers) about 1,710,000,000 square feet, while the movement at Minna Bluff—probably a maximum area for speed—is 492 yards a year, the rate of move- ment towards the eastern end of the Barrier must be extremely slow, perhaps almost negligible, as Amundsen suggests. The rate of 492 yards a year is nearly 4 feet (1°22 metres) per diem. It may be assumed that as the eastern end of the Barrier is almost stationary, the mean rate of advance is not more than about 2 feet a day, though it is quite possible, as the Minna Bluff speed is probably a maximum, that it may not exceed about 1 foot per day. At the 2 feet per diem rate of advance 3,420,000,000 cubic feet of ice would be added to the sea-cliff face of the Barrier daily. At the rate of advance of 1 foot per day, 1,710,000,000 cubic feet would be the daily addition. As already stated, on the assumptions made, the outlet glaciers from Skelton Inlet to the Beard- more Glacier, inclusive, contribute in summer perhaps about 1,000,000,000 cubic feet daily. To this must be added— (a) Ice contributed by outlet glaciers not examined by us, such as the ice of the glaciers discovered by Amundsen, the Liv Glacier, the Axel Heiberg, and the Devil’s Glacier, and probably other glaciers between the Liv and Beardmore Glaciers, as well as by glaciers between King Edward VII. Land and Carmen Land. (>) Numerous Alpine and Norwegian types as distinct from outlet glaciers, chiefly on the east side, partly on the west side of the Ross Barrier. (c) Strips of old bay ice (sea ice) bridging over what would otherwise be lanes of open sea water between the edges of the glacier ice jetties. (qd) Drift snow and new-fallen snow deposited on the actual surface of the Barrier. Obviously the December summer rate of movement of the outlet glaciers which feed the Barrier cannot be maintained during the winter months, and so the December rate of perhaps 1,000,000,000 cubic feet of ice daily may be distinctly less in winter time. These figures are of course only roughly approximate, though based on the best measurements available. Nevertheless they serve to show that the suggested sources of nourishment of the Ross Barrier are reasonably competent to support this magnificent floating piedmont, provided ablation over its surface did not * Ferrar states (op. cit., p. 82) that Lieutenant Barne’s measurements show that the Ross Barrier near Minna Bluff moved 608 yards in 134 months. Our measurements extend over a period of 64 years. ALIMENTATION AND DENUDATION OF THE ROSS BARRIER 143 exceed annual precipitation, and provided also that there were no loss of ice to the Barrier owing to the constant melting of its under surface in the relatively warm deeper water of Ross Sea. We know that both ablation and melting, chiefly submarine, are now contri- buting to remove the ice of the Barrier above and below simultaneously. On the whole the Barrier surface * is probably gaining, especially along its southern, south-western, western, and central portions through accessions chiefly of drift snow, partly of snow falling 2m setw on the Barrier. For example, at Captain Scott’s Depot “A,” near Minna Bluff, the accession of hard snow, almost névé, proved to be no less than 8 feet 2 inches (2°5 metres in round numbers) in 64 years, that is, almost exactly, 15 inches (380°99 millimetres) of hard snow, which was proved by experiment to be equal to 7} inches of rain (184°15 millimetres) a year. As already explained in the Meteorological Notes, the part of the Ross Barrier nearest to the high mountains of the Antarctic horst and nearest to the sea receives the heavier additions of drift snow, as well as of snow falling 7 situ. Amundsen records that the surface of the Ross Barrier, between about 80° and 82° S. lat., and near the meridian of 163° W., did not alter appreciably between April 1911 and October 1911.7 This area, removed so far from the nearest high mountain, is one of comparative calm, and consequently low snowfall and little drift snow. The loss to the Ross Barrier through the constant melting of its base in the relatively warm water of Ross Sea is probably considerable, possibly even approxi- mating to about 1 yard (‘914 metre) to 1 metre a year. Thusas fully sixty years have intervened between the time of Captain R. F. Scott’s survey of the Barrier in 1902 and that of Sir J. C. Ross’ original examination of it, at the rate of a yard a year no less than 60 yards 180 feet (55 metres) may have been removed by melting from the base of the Ross Barrier. Date of latest Phase of Maximum Glaciation. (a) Vertical Shrinkage of Ross Barrier. If the mean density of the Barrier Ice be taken as °85 as compared with the average density of the water of Ross Sea taken as unity, the height of the Barrier cliff may have been lowered by as much as 32 feet (over 9 metres) from this cause alone since the time of Ross’ visit in 1842. Unfortunately Ross’ survey was not sufficiently detailed to prove whether or not such an actual general decrease in height has taken place. If data were available as to this present rate of dwindling of the ice of the Ross Barrier, some approximate estimate might be formed of the time that has elapsed since the latest phase of maximum glaciation in the Ross Sea region of Antarctica. As has been abundantly proved already, the surface of the Ross Barrier has * But this surface gain may be more than compensated for by the submarine melting. + The South Pole, vol. i. pp. 233, 234, and 382. 144 GLACIOLOGY shrunk vertically by about 700 feet, near Cape Crozier, since the maximum glaciation. At this time the Ross Piedmont was obviously aground, but, with diminished snow- fall on the firnfelds of the feeding glaciers, a time must have come when the Ross Piedmont floated off the bottom and its base commenced to thaw. At the rate of thaw of a yard (‘914 metre) a year it would have taken the Barrier only about 400 years to have floated vertically through the amount of about 200 fathoms, which is near the average amount. To this would have to be added the time needed for the lowering of the Barrier surface from 800 feet above sea-level to about 300 feet above sea-level, that is, a lowering of about 500 feet. There are no data known to us for estimating this. (b) Horizontal Shrinkage of Ross Barrier. On this question the evidence is a little clearer. From 1842 to 1902 the seaward edge of the Ross Barrier has retreated southwards some 20 miles (32 kilometres) on the average in sixty years. Evidence has already been given to show that the Barrier front was formerly at least 200 miles north of its present position. At the above rate of recession the Barrier front may have retreated all the way from the latitude of Cape Washington down to its present position in so short a period of time as 600 years, which seems scarcely credible. Probably the rate of recession at first, when the ice of the Ross Barrier was about 2500 feet thick on the average, was far slower than at present, when its average thickness is only about perhaps 720 feet. Even if the rate was formerly three times as slow as at present, it may all have taken place in about 1200 years. Of course a very considerable amount of time may have elapsed during oscillations to and fro of the Barrier front during the latest of its maxima. Accurate soundings of the whole of Ross Sea would no doubt throw much light upon the positions of the Ross Barrier front during various maxima of glaciation. Such evidence might be afforded by submarine ridges formed of push moraine or dumped moraine.* Future Observations. It appears to us that in addition to detailed soundings future observers might profitably direct attention to the following problems in con- nection with the Ross Barrier :— 1, The trend of individual glacier ribs or fans. 2. The trend of the undulations of the nature of gentle pressure ridges and troughs more or less normal to the path of the main glacier streams. 3. The presence or otherwise of sea ice just south of low-lying portions of the Barrier cliff, and the amount of névé and ice overlying it derived from old snow. This might be ascertained by boring and recovering the core of ice from the bore from time to time, or by studying the character of the ice in these low-lying portions of the Barrier in the sides of any convenient crevasse situated at some distance south of the Barrier edge. * It is understood that Commander E. R. G. R. Evans, R.N., of Captain Scott’s expedition, as well as Lieutenant Pennell, R.N., of the same expedition, have lately obtained, when sounding on the Terra Nova, important information on this subject. POSSIBLE LINES OF RESEARCH FOR FUTURE EXPEDITIONS 145 4. Serial temperatures at various depths in the ice of the Barrier might be obtained either from bores or crevasses. 5. Serial temperatures all along the Barrier edge are very much needed. 6. Rate of melting of ice blocks at various depths in Ross Sea along the Barrier edge, as might be ascertained by the method already suggested, which could be employed at sheltered inlets like Bay of Whales or Western Inlet. 7. Direction of currents under the Ross Barrier (#) at McMurdo Sound, () under the main face of the Barrier. This could be ascertained with a deep sea current meter at Bay of Whales, Western Inlet, and the shallow bight where the Barrier is only 15 feet (43 metres) high at a point 250 miles E.S.E. of Cape Crozier. 8. The rate of movement, if any, of the Ross Barrier along its eastern margin between Carmen Land and King Edward VII. Land, as well as many more observa- tions of the movements along the western side of the Ross Barrier, are also much needed. 9. The granulation and crystallinity in general of the material of the Ross Barrier at various depths has at present been very little studied.* 10. The relation of ablation (loss) to precipitation (gain), whether the latter results from falling snow, drifting snow, or contributing glaciers. No observer interested in the phenomena of the glaciation of Europe during the Pleistocene Ice Age can fail to be struck with the very important analogue of the great Ross Piedmont to the vast sheet which formerly stretched from Scandinavia to the northern part of Great Britain, filling in the North Sea. Just as in the case of the smaller Antarctic Piedmont of the Drygalski-Reeves area, and the far larger Ross Piedmont, one can imagine that, like the Ross Barrier, the old North Sea Barrier was during the ice maximum everywhere aground except where it floated over the depths of the Skiiger Rak. One sees the great glaciers of the Christiania region, as well perhaps as those of Christiansand, Stavanger, and Hardanger, sending out far-reaching ice jetties or fanned-out piedmonts towards Great Britain. These ice jetties, at first separated from one another by open lanes of sea water, eventually coalesce, either through their edges coming in contact, or more prob- ably through being linked up to one another by wide strips of old bay ice, the sea ice in such sheltered lanes between the ice jetties not breaking away during the summer, as sea ice does in more exposed areas, but gaining in thickness from year to year. Its thickness meanwhile would be further increased by accumulations of drift snow and falling snow. This probably was the manner of the building of the great ice raft, or rather ice sledge, which drove eventually * ©. 8S. Wright, Physicist to Captain Scott’s recent expedition, has, we understand, an important series of observations on this subject. 7 Mr. Wright concludes (“ Scott’s Last Expedition,” vol. ii. p. 449) that the Ross Barrier Edge has neither receded nor advanced between 1904 and 1912. We may remark that it is nevertheless possible it has become thinned through submarine melting. 146 GLACIOLOGY past the Dogger Bank against the eastern shores of Northumbria, and thrust and glaciated and over-rode part of that coast at a distance of 400 to 500 miles from the Norwegian glaciers, just as to-day the Ross Barrier is thrusting and over-riding and glaciating Cape Crozier at a distance of some 300 miles from the contributing glaciers ; in spite of the stemming action of Ross Island which leads to the develop- ment of great pressure ridges and shear planes along the zone of contact between land and ice. It must be remembered too that some of the ice at the Ross Barrier edge has advanced fully 500 miles north of where the soles of the Heiberg and Devil’s Glaciers leave the shore-line, and that formerly, during the maximum glaciation, that edge was even 700 miles north of where those glaciers left the shore, and that, though aground for this entire distance, the piedmont still could move forward and grind and heavily glaciate the hard volcanic rocks high up on the shoulders of Ross Island. The individual glacier ribs or ice jetties of the North Sea Piedmont may be compared to the runners of a sledge, while the bay ice between represents the sledge decking. The friction of this superstructure (carrying its load of old snow largely granulated into ice) on the sea floor would be reduced to a minimum by the glacier runners, the bay ice between these “runners” being afloat. (See actual section in this report of the Drygalski-Reeves Piedmont in Ross Sea.) But such runners should scoop out grooves in the sea floor. Do the soundings of the North Sea reveal the presence of such grooves? It is doubtful whether such can now be traced, but it must be remembered that if again we judge by the analogue of the Drygalski-Reeves Piedmont there is a distinct tendency after the grooving effected by a glacier “runner” during a maximum glaciation for the “runner,” as it gradually floats up out of its groove during deglaciation, to aggrade that groove, at all events for a distance of many scores of miles to the seaward of the coast-line, and tidal scour and other marine currents should help this work of aggrading. In the case of surface-carried moraine material, which as Antarctic experience shows would soon become englacial, there is no limit to the distance out to sea to which aggradation may take place, other than the length of the extension seaward of the glacier, and the limit of the drift of its icebergs. It is possible that detailed soundings of the North Sea will yet reveal traces of under the North Sea Piedmont during the ? the grooves of the glacier ‘runners’ Great Ice Age. PLATE XL SHOWS THE THAW AT GREEN LAKE, CAPE ROYDS. DURING THE SUMMER OF 1908-9 | Zo face p. 146 CHAPTER VII LAKES AND LAKE ICE OF CAPE ROYDS AND CAPE BARNE Lakes and Lake Ice. The lakes which occupy the ice-gouged depressions of the peninsula of Cape Royds are of special interest. Owing to their accessibility during the winter these lakes were examined in detail, and one or more trenches sunk in all the more important ones. There are several lakes deserving of a separate individual description, but the majority are small tarns, in winter occupied by a sheet of ice generally less than 3 feet thick. The ice in these tarns, unlike that in some of the larger lakes, was found to melt entirely in the summer. In all the large lakes, and in some of the smaller, there flourishes a brown to reddish- brown algous plant, which in some cases grows to such an extent that the accumula- tion of vegetable matter resulting from its decay forms a layer of peat. of appreciable thickness on the lake bed. It seems probable that many of the smaller lakes which contain little or none of this alga are not permanent, that is they may be entirely removed during the winter and spring by ablation, or in the summer by thawing. This was proved, in the case of some of the extremely small lakes, by our had already by late November taken the place of the smallest of the tarns. Many of these, how- ever, were refilled from time to time from the thaw-water of snow-drifts on the slopes observation that small depressions—coloured green by an algous growth above them, and it was only at times of prolonged drought, when there was no snow falling or drifting, that the depressions became quite dry. It is probable that these lakes are in the majority of cases sub-permanent, since the thaw-water from the drifts of late summer, when the sun does not rise high above the horizon, and thus does not exert much heating influence on the rock-basins, would become frozen, and would remain so until the tarns were entirely removed by evaporation, or until the next summer thaw set in. There is no doubt of the permanency of the larger lakes, although there are evidences showing a considerable restriction in size in some cases. These evidences will, however, be dealt with when considering the lakes individually. The ice and water of most of the lakes is more or less salt, though there are apparently one or two important exceptions, and this saltness is due probably to a combination of two causes: (1) Wind action—decidedly the most important ; (2) filching of salts from the kenyte. 147 148 GLACIOLOGY 1. The wind brings salt to the soil and to the lakes in two main ways. In the short summer, during the heavy blizzard of February 17th, 18th, and 19th of 1908, the sea spray in a frozen state was carried by the wind for considerable distances in- land. Such action as this, although the high winds during this season of the year are few in number, must have no inconsiderable effect on the waters of those lakes which melt in summer, for not only do they receive the spray which is dropped immediately on them, but also a large quantity of that which falls on the slopes of the hills surrounding them. ‘The latter is carried into them by small streams of thaw-water in the summer. In that portion of the year, when the sea is frozen over, the method of transport is different, but the quantitative result must be even greater. Every blizzard brings quantities of drift snow which has been lying on the sea ice, and has been infiltrated with the salt extruded from between the crystals of the sea ice, and some of this snow (although large quantities pass on beyond Cape Royds towards Cape Bird and the Ross Sea) is formed into drifts on the lee side of the hills and ridges, and subsequently in the thaw season goes to swell the amount of water in the lakes. 2. The second cause appears to be less significant in the Cape Royds area, as here the denudation seems to be more mechanical than chemical. The chemical leaching by the thaw-water is much better illustrated in the Western Mountains of McMurdo Sound, and will be considered in the section dealing with that portion of our researches. Nevertheless, it is probable that a certain amount, at any rate of the soda salts, is leached out from the kenyte during the short period when the thaw is sufficiently effective to produce rivulets of water leading down from the snow-drifts to the lakes. The waters of the lakes may be further mineralised by other local causes, which will be dealt with when considering them separately. The main glacial groove in which the larger lakes are situated passes from the head of Backdoor Bay along the length of Blue Lake, and sends a branch to the coast by way of Clear Lake and Coast Lake, while the main valley continues as a broad depression filled with morainic material in a north and south direction. (See Plate XLI. Fig. 1.) Two lakes near Cape Barne, Sunk Lake and Deep Lake, appear to be situated in a continuation of the same valley, whilst the other im- portant grooves appear to run more or less parallel with this one, as, for instance, that which the tripartite Terrace Lake occupies. (See Plate XLI. Fig. 2.) The remaining lakes or tarns are situated in the depressions which are essentially characteristic results of the phase of denudation which is so typically illustrated here. All angles and craggy projections have been rounded by the Great Ice Sheet, and a mantle of morainic matter of varying thickness has been deposited on top of the country rock, while through this mantle bosses of the more resistant types of kenyte project here and there. Green Lake. Green Lake lies about half-way between Blacksand Beach and gFL a anf oy, | ge RE OE ig » VIN ALV Id 149 LAKES AT CAPE ROYDS ‘SDIEMUMOP pazUNOUad 310 SaL/0IaQ YIIYM 67 “SI OE ong 3334 001 0s 0 £ 2 “suieu) 1 0 re *aje2S ed1940A ‘aleIS jeulpnqibuoy jana/ eas / a7huay | \ ( yy! 9 YEYS s7jeua ayqqni arkuay ‘sodap 71 472auaq ‘ a/UBID pue sa/qgad auiesow snobiy 4ajem Kuug $0 7005) 471M 87/00 payirijig velgwez 40 DUIsAAO? UiYL HIYT SUL IFG 9I! 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It occupies a fairly shallow basin, completely surrounded, with one exception, by high ground, and must receive the drainings from a relatively considerable area. The one exception is a snow slope towards the sea, which connects with the lake itself, and would serve as an emergency outlet if the thaw-water in summer caused any sudden rise of the waters of the lake. To the north-east and north it is bounded by ridges which run back to a knotting point near the top of the High Peak, whilst to the east and south-east the ridges and small hills stand some way back from the lake, being separated from it by a very gradually shelving slope, 100 yards broad, of morainic gravel of small sub-angular kenyte fragments with a sprinkling of larger boulders of kenyte and foreign erratics, such as the silicified oolites which we suppose to have analogy with some of the sedimentary rocks at the head of the Beardmore Glacier. A very slight accession of water or ice to the lake would, if the outlet on the seaward side were blocked up, cause the addition to the lake bed of a considerable area of the shelving plain. To the south the lake is bordered by ridges running east and west, which end near the sea ina hill of some size, which is marked on the map as Red Flag Hill. On the shore side of this hill is a fairly large snow slope which, being sheltered from the southerles by the hill itself and on the north by High Hill and its ridges, is one of the most permanent snow-drifts on the peninsula. On the west the lake is bounded by the sea, and is separated from it by the snow slope already mentioned, and by ridges and knobs of kenyte, which again end in a small rounded hill of a very typical shape. On this side of the lake are two large erratics, one of aplite and one of grey granite. The lake itself is between 90 and 100 yards in greatest length from north to south, whilst its breadth varies from 100 yards to 45 yards. Its surface is smooth, even glassy, and is traversed in winter by numerous contraction cracks due to the great cold. These cracks after a spell of comparatively warm weather have been observed to become appreciably smaller, and in summer many of them closed al- together and were recemented by regelation in some cases, and in other cases, where the expansion of ice did not quite cause them to join up, by thaw-water from the sides of the crack. The space between the sides of the cracks might also be reduced through the addition of thin layers of ice formed by the freezing of aqueous vapour on the walls of the crack. On one occasion whilst we were working on the lake we were surprised by a series of reports like pistol-shots and by the appearance of cracks, and the cause was explained when we returned home. After inquiring of the meteorologist we found that the temperature had dropped from —3° F. to —21° F. in considerably less than two hours, so that the cracks were obviously contraction cracks. LAKES AT CAPE ROYDS 151 The state of the surface changed considerably from time to time, for, although generally rendered glassy and smooth by ablation, yet after a heavy blizzard before the sea was frozen over the ice would be rendered very sticky by the sea spray ; in fact the resemblance to a smooth sea ice surface was remarkable. Then, again, after heavy blizzards portions of the lake near the shore would become covered with snow. These drifts would persist for long periods before being removed by ablation, and it was apparently on the underside of these drifts that the very macrocrystalline prismatic lake ice was chiefly observed. Indeed the only places on Green Lake where this form of ice was developed were those which were from time to time covered by these drifts, although on other lakes, notably Clear Lake and Blue Lake, the prismatic ice played a much more important part. By the contour of its basin there was reason to believe that this lake was nowhere deep, and this belief was afterwards upheld by our trenching work. The total depth of the lake at the spot where the shaft was sunk proved to be 6 feet 4 inches. Algous Deposit. There is practically no deposit on the southern shores of the lake ; to the east it is scattered up the gravel slope for some distance, and pieces occur many feet above the present level, but the sprinkling is very sparse except for short distances along within 2 feet of the ice margin, where it is in places fairly common. The principal deposit is at the north end. Here the width decreases from a belt 12 paces wide at the north-east corner to one 6 paces wide at the north- west corner, and three distinct ridges raised sharply 1, 2, or 3 inches high are well marked at 3, 4, and 5} paces from the lake border. We believe these ridges to be due to a combination of two causes. The presence of sparse fungus along certain levels on the whole of the north and east side and half the west side of the lake seems to indicate that these definite levels mark the surface of the ice at certain definite periods of recession of the lake. On the other hand, the thick algous deposit at the north, and particularly the north-west end of the lake, tends to the presumption that it is due to the influence of the prevalent southerly winds in the summer when the lake is thawed, and that the ridged appearance is due to wave action, and this view was further strengthened by the way in which during a heavy drift-laden gale in February 1909 the slush in the lake water was piled up on the leeward side of the lakes in similar ridges. Convexity of Lake Surface. On June 22nd it was noted that a main crack running east and west had appeared at the southern end of the lake, and that the ice to the south of this was tilted up towards the crack at quite a perceptible angle. This convexity of the lake surface was, however, better seen and photographed in some small tarns at Cape Barne, and will be dealt with under the Cape Barne section. Trenches in Green Lake. On June 24th to 26th, 1908, the first trench was sunk in Green Lake, and temperatures were taken by Murray at every 6 inches during the 152 GLACIOLOGY working. The superficial dimensions of the trench were 3 feet by 7 feet, and the ice proved to be 5 feet deep. There was water under the ice, but the supply was limited, as shown by the fact that when tapped it only rose quickly to within 2 feet 6 inches of the top of the ice, subsequently rising another 6 inches in an hour. This rise was probably due to a slight sagging of the ice, and also to the release of some of the water held under pressure in the bottom 6 inches of the ice, and which would only disengage itself slowly. There was scarcely a foot of liquid left under the 5 feet of ice, and from the slowness with which the water rose in the trench it seems probable that we tapped the lake at one of the few places where a little brine solution was left unfrozen. This brine solution was at the remarkably low temperature of 21° F., and some which we bottled we left to stand for some time, when a ring of oily material about $ inch thick with a greenish fluorescence was formed at the top. This was formed of tiny globules, each about z}5 of an inch in diameter, with a refractive index lower than that of water. It was afterwards masked by a brownish-yellow scum, with a thickness of quite an inch in parts, and a quantity of evil-smelling gas was given off. A quantity of the ooze from the bottom of the lake was also collected. On Fig. 55 is shown the shaft sunk by one of us in this lake ice in June 1908. Descending Section. A. Ten inches of ice with numerous air bubbles. (Four inches of fairly clear ice then a layer of bubbles, 3 inches of ice and then a layer of bubbles, then layers from an inch and a half to half an inch separated by regularly arranged rows of bubbles.) B. Three feet 2 imches of typical lake ice, very bubbly, and with some bubbles drawn out. A falsely fibrous structure becomes more and more apparent as the lower layers are reached, its cause being apparently streams of very fine bubbles in a vertical direction. The bubbles are fairly uniformly distributed. C. At 4 feet the ice became yellow and discoloured, with a very unpleasant smell, due to gases given off. It was also very salt and moist, and all three characteristics increased as the work proceeded. Type A. The structure of this ice is very interesting, and appears to be due to atmospheric conditions. In the late summer, when the lake began to freeze over, the layer of ice formed when the sun was low was at first entirely removed when the sun’s rays impinged on the lake at a steeper angle. As the winter approached, and the hours when the sun was high enough to affect the lake decreased, the ice became permanent, and apparently the first permanent layer of ice formed was suffi- ciently thick to leave a layer of 4 inches at the end of the succeeding day’s thaw. Dur- ing the succeeding period of comparative warmth before another frost set in, and when the first layer of ice was being removed (as thaw at the time was dominating freezing), a number of gas bubbles, disengaged by the decay of the organic matter at the LAKES AT CAPE ROYDS 153 bottom of the lake, rose towards the surface, and accumulated under the sheet of ice. The succeeding frost added to the bubbles owing to the air and gas in solution in the water being expelled mostly above or below the new layer of ice formed. This frost was evidently of a sufficient duration and power to add 3 inches of permanent ice to the lake covering. The same process was repeated again and again, with the dif- ference that as the non-conducting layer of ice on top of the lake increased in thick- ness, and the remaining solution became more saline, the frosts, although becoming more severe as the autumn approached, were unable to effect as much freezing of the water as the earlier frosts, and thus each day’s layer of ice decreased in thickness until the daily variation of temperature ceased to have effect, and the second uniform type ice of ice (Type B.) began to form. Type B. This was the ordinary type of lake ice of uniform and slow growth. The noticeable fact about the ice between 2 and 3 feet below the surface was the gradual inception of the pseudo-fibrous structure and its analogy to sea ice. This is, however, natural, for it is presumably due to the same reason as the fibrous structure in sea ice, namely, to the extrusion of the salt as a highly concentrated brine solution in a series of little globules, forming thermometer-shaped tubules, outlining the ice prisms. Type C. The discoloured and odoriferous nature of this last ice is due to the ice being saturated under pressure with a strong solution of gases in brine, the most prominent ingredient in which solution is sulphuretted hydrogen, probably produced by the decay of the algous material so common in all the lakes at Cape Royds. Mawson found that some of this brine solution froze at as low a temperature as 50° F. below freezing point. Temperatures. A series of temperatures taken in the trench is as follows. Mean air temperature, June 24th, 25th, and 26th, was —7:2° F. June 24, 1908. June 25, 1908. Surface : : : é 5 SONS Tay = 10}? 1D 6 inches ; 5 , 5 5 | = Oa 18 = CHS 1b QR ose : : ; : 5 = fx0e! 1a = 70? 1, 380 5 : : 3 : 5 = SOP IR, = pO} ING 24, F : : : 0: Ont — 3:°5° F. 30°, 1 30" Le = less" 12, ORES +- (6:00 Bi. FE less 1 42 a ; : é ? 5 a tee Tee + 6:0° F. 48s, : A ; : : fia +10:0° F. Ay Ts : ; ; ; : 3 SE als pay 1, GOR 5, , ‘ F : Fi due + 19° F. Brine solution : : : 5 cee + 22° F. The comparison shows a general but by no means uniform adjustment to the air temperature. Second Trench in Green Lake, July 31st, 1908. The section was as in the first 154 GLACIOLOGY trench, but the yellow ice started at 2 feet 6 inches and the ice was almost 5 feet 6 inches thick, reaching to within 3 or 4 inches of the lake bottom. In making this section two master cracks were used to lighten the labour at a place where they crossed at right angles, and incidentally it was proved that they were open right to the bottom of the lake, as the trench was scarcely 3 feet deep when the brine solution oozed up very quickly along both of the cracks, and it was necessary to desist and cut a trench within a trench. The work was much inter- rupted by other duties, but the bottom 18 inches was taken out on August 6th, when the section exposed was as follows :— A. Ten inches of laminated ice as in Trench 1. B. Twenty inches of colourless ice, opaque, with fine bubbles and salt extrusions. C. Thirty-six inches of ice similar to above, but of yellow colour and very malodorous. After the ice was broken through the water rose only 24 inches in the trench. Specimens of ice from the sides of the shaft at different depths were examined by Mawson, and bottles of the brine solution were collected. The latter was similar in colour and consistency to that of the former trench, but nothing like as much gas was given off. It seems likely, therefore, from consideration of this last fact, and the little height to which the water rose in the trench, that this second trench was cut down into the same reservoir of the brine which we tapped last time, that this solution is the last concentrate produced from the water of the whole lake, and that the part of the lake in which we trenched is the deepest. Temperatures taken on July Ist were— Surface (1 inch in) : : : - é ; . — 23° F. 94 inches. ‘ j ; A F : , . —23° F. MS) ap : : : : : ‘ : : 5 =e in Beenie” ee cw ws.) fae gee Ms PE sian Bhs} gp : : 3 ; : : é : a Secu 474, : - ‘ : P ; : : 2) = Por The temperature of the brine solution taken immediately we broke through the ice on August 6th was —17° F., probably one of the lowest temperatures ever re- corded for so large a body of water under natural conditions. Clear Lake. Clear Lake is situated to the north-west of Blue Lake, and in the western fork of the northern continuation of the Blue Lake Valley. Its name was given to it because of the remarkable clearness of the upper layers of ice. There were few striking topographical features immediately near the lake, but one was a steeply-rounded kenyte knoll, whose sides sloped rapidly down right underneath the lake, and a few yards out from which, to judge from the contour of the lake basin, the deepest part of the lake should be situated, for everywhere else the slope LAKES AT CAPE ROYDS 155 of the lake shores was quite gentle. This steep rock slope is seen to the extreme left of the lake shore in the photograph, Plate XLII. Fig. 2. It was near this knoll, and with the object of tapping the deepest part of the lake, that our first trench was made. Another important feature about Clear Lake was the terraced condition of the slopes immediately above the present lake level. At the north-west end especially there were well-marked traces of terraces in the morainic gravel; these terraces were each from 1 to 2 feet high, and may mark periods of rest during the recent recession of the lake. First Trench, cut on March 30th. This trench was, as mentioned above, near the kenyte knoll, and there proved to be then only 4 feet 3 inches of ice. The top 4 inches of ice is coarsely crystalline, with wide opaque divisions between the more or less hexagonal prisms, and may be the result of the conversion into ice of the lower portions of snow-drifts by the thaw, such conversion having taken place in crystalline continuity with the prismatic ice formed each year by the re-freezing of the water of the lake. The individual crystals are not at all regular in shape, being often most intimately interlocked, and frequently arranged in curious patterns, with a peculiar radial structure, as if they had grown outward from a central prism or group of prisms. This roughly radial arrangement of prismatic ice seems quite common in the older moraines on the Ferrar Glacier, and there is no doubt about its origin there, for it is formed in almost every case by the freezing of the thaw-water after a boulder has thawed its way down below the surface. The Western Party saw in such cases the process in all stages, from the boulder that is just commencing to sink in, to the rock moraine where not a boulder is to be seen, and their former presence is only indicated by these radial patches of prismatic ice in coarse hexagons. The structure seems here to be distinctly a secondary one, for although in a few cases hexagonal plates of ice were observed on the surface of thaw-water lymg in hollows in the ice, it was far more usual for the first layer of ice at any rate to form as small acicular needles radiating from every projection, and the ice sheet newly formed presented to the eye an apparently homogeneous structure. It seems therefore that in this latter case at any rate some molecular rearrange- ment takes place, with extrusion of air as minute air bubbles outlining the crystals. It is suggested that this is a secondary structure superinduced upon ordinary thaw- water ice. In the case of the prismatic ice on the lakes it was more difficult to see any preliminary stages. . The surface ice was either ordinary thaw-water ice, or the hexagonal prismatic ice was there in its finished condition. It seems probable that in the lakes, where the freezing is undisturbed by the movement of the water, the ice forms in vertical hexagonal prisms, as was undoubtedly the case in the Narrows of Blue Lake, where the separate prisms could be traced right through the ice. The thawing of the snow-drifts then proceeds in crystalline continuity with 156 GLACIOLOGY the lake ice, and the resultant prisms are sharply outlined by air globules forced out between the crystals. Some explanation of this kind is necessary to account for the domed and uneven surface and great thickness of this variety of ice in the southern half of the Blue Lake. This change, of whatever nature it may be, always takes place in the snow of snow-drifts where there is little lateral pressure, and it is quite conceivable that if a molecular change took place, resulting in the formation of well-marked hexagonal prisms, it should be accompanied by the extrusion of the air from the ice, and in this air being forced into position as minute bubbles along the lines of natural weakness, that is, between the boundary faces of the different crystals. The top layer of prismatic ice, 4 inches in thickness, as just described, was followed by 3 feet 8 inches of ordinary lake ice with some air 4.inches. A. bubbles. Beneath the ice was 13 feet of slightly brackish water. The bottom material proved to be a deposit of black, evil-smelling mud containing diatoms, some of excep- tionally large size, pieces of decayed algze of small species, several living species of Rotifera and Tardigrada (Water- bears), and some obscure bodies which may possibly be spores, but have not been determined. This deposit was about 6 inches thick, and was succeeded by the typical morainic gravel. Second Trench in Clear Lake, April 14th, 15th, 16th. SH ins. 1D A. 4 inches of prismatic ice. B. Ice with air and gas bubbles in it 1 foot 8 inches. C. 3 feet 4 inches ice with drawn-out bubbles giving Fic. 50 prismatic structure. D. 3 feet 9 inches ice with bubbles. The difference of thickness of the ice in the two trenches is easily accounted for by the presence near the first trench of the large knoll of intensely black kenyte, the influence of which must have been very considerable in regulating the amount of thaw which had taken place during the summer just past. One other feature of this lake worthy of mention was the occurrence at a depth of 2 or 3 feet of what was apparently a well-defined ablation-rippled surface with the depressions between the ripples still filled with snow, and also at the same level of strings of what we called snow-tabloids, lenticles of air in the ordinary lake ice partially filled with a loose powdery ice. Temperature at the Second Trench at Clear Lake. Mean Air Temperatures, April 15th : 2 ; . . —10-4° F. * » 16th : : : : 5 = MG? 10, 5 peal A ; : : a SHAG}? 10, PLATE XLII ie Fic. 5. ESKERS OF BLUE LAKE, CAPE ROYDS Showing adjacent ice slope formed out of snow-drift by a process of secondary crystallization [Photo by T. W. E. David Fic. 2, VIEW OF CLEAR LAKE, NEAR CAPE ROYDS, LOOKING TO N.W. | Photo by T. W, E. David Fic. 4. BLUE LAKE, NEAR CAPE ROYDS Looking north-westerly. In the middle distance is the dyke which almost isolates the northern and southern parts of the lake. The esker mounds are on the near side of the gap in the dyke, “the narrows ” a2 ESS SESS SS Se : iat — Fie. 6. COAST LAKE, LOOKING SOUTH-EASTERLY The bottom of this lake is covered with algal peat [To face p. 156 LAKES AT CAPE ROYDS 157 April 15th. April 16th. 4inches . : é s : : » =i6° BF: 14 F : F , , : a oo aR. 2s : E : : J : : 0° F. PHS) oo : : ‘ ‘ : ; B BEG? 10. Bi) : j ‘ ; : : 5 > by ane Om M Ve wee BOF 4955; j ‘ : ; : : . +10°8° F. 5Gls : : : 5 : , 5 SS IHS") 120 6s ee ee ae oour: 66. ; F ; : : : a teal ne Xe WA 5; +17:7° F. SOs + 20° F. 50; + 22°5° F. 960 ;; lO ay(/= Ii 102) + 28°8° F. Surface temperature on April 16th was. - : : —12°F. Water, 1 foot from bottom : 5 : ; ; i + 35° FF. Below the ice at this point there was 4 feet of water, the lake here being only 13 feet deep. The layer of ice from 2 feet down to 5 feet was quite fresh, but that tested both from above and below these levels was slightly brackish. There is much less alga in this lake than in Green Lake and Coast Lake, and both water and ice are appreciably purer, although there is even here enough decaying organic matter to render the smell of the mud at the bottom very disagreeable. Blue Lake. This lake is situated in the main glacial valley of the Cape Royds Peninsula, being really part of the boundary between the peninsula and the main- land of Ross Island. Its southern end is partially blocked by a knoll of kenyte with large snow-drifts on either side of it, while on the southern side of this ridge lie slopes of nevé and drift snow, covered with a layer of frozen spray, which form part of the ice foot of Backdoor Bay. On the eastern or Erebus side the lake is bounded along its length by the snow slopes of the mountain, which are interrupted at intervals by terrace-like accumula- tions of morainic matter. To the south-east these snow slopes are broken, and bounded by several strongly marked hills of kenyte, to the largest of which the name of Sentinel Peak was given. South of this peak is a dried-up lake, the bed of which is covered with an accumulation of soil containing diatoms and alge. The western side of the lake is bordered by the kenyte of Cape Royds, knolls of massive rock standing out between slopes covered more or less thickly with morainic debris, while here and there snow-drifts repose in semicircular hollows between divergent ridges. These drifts are sometimes of sufficient importance to be underlain by considerable névé deposits. The lake is divided into two distinct portions of about equal size by two sharp ridges of kenyte, which traverse it from east to west, and have a gap of only 10 to a 158 GLACIOLOGY PLAN OF Ross Ilsland. Scale of chains 10 20 5 \ 5. Nagrows Rouno aaa ‘ \ , / TRENCH Twin PE $% * . “ “ Tarn 7 8 Se) ez r ae Aenyt. Nip ce *7win par 20F Rea e Aidge > ere, UESKEs ‘ S Tye poe =e Sharpe ow BOOS oa i) Te NE OMS =>) Ss = ® QWNUNATAK a 1 > = (> Mpple ™m 2 i id En % Ai ssPriestley P& Soo UF TR AP OENUYNE! True Meriaian HECR Fie. 51 LAKES AT CAPE ROYDS 159 15 yards between them, and which are probably the remains of a dyke of kenyte more resistant than the other rock from which the valley has been scooped. In the southern half of the lake there are a group of circular eskers of morainic gravel ; one or two of them are double eskers, with their long axes directed north and south. (Fig. 45, Chapter VI.) Plate XLII. Fig. 5 illustrates these small esker mounds, which are from about 5 to 8 feet high. Adjacent to them the surface of the lake ice has been added to by the formation of coralloidal ice out of the lower portions of snow-drifts. First Trench, July 8th to July 20th. This trench was sunk in the southern half of the lake. There proved to be 15 feet of ice of very uniform character resting on an ice-cemented breccia of kenyte and erratic gravel. The ice was free from salt, and this is remarkable, considering that the lake is swept from end to end by the southerly gales blowing from over McMurdo Sound. During the summer 1907-8 this portion of the lake does not appear to have been melted, and the only effect of the thaw from 1908 to 1909 was to make the hexagonal prismatic ice on top very rotten, and to cause the individual crystals to be separated, as the thaw proceeded with greater speed along the opaque boundaries of the prisms than elsewhere. There are evidences which tend to show that the lake has been partially or wholly melted during exceptionally mild seasons. The following section illustrates the structure of the ice in our main shaft at Blue Lake (Fig. 52) :— A. A layer a few inches thick of clearly crystalline ice, generally showing a hexagonal prismatic habit, but with many of the prisms very much dis- torted in shape, and with strong white partings between the crystals. This type appears to be separated from the ice beneath it by a brecciated and strained layer, possibly caused by differential horizontal contraction and expansion between the types A. and B. B. Clear pure ice of remarkably uniform character, though the air bubbles were much more numerous for a foot or two below the prismatic ice than at deeper levels. The main characteristic of the ice of this lake was its conchoidal fracture, which was very marked, and in the lower portion of the ice the fracture planes of the frag- ments were generally indicated by fine concentric flutings. A coarse radial ribbing was also common across these same faces. The ice was also traversed by fracture planes, sometimes several inches in diameter, and generally roughly arc-shaped, which were very strongly recemented, so strongly that when struck against the shaft of the pick the ice showed a marked tendency to break at an angle with the former fracture plane rather than along it. Three or four types of this ice were distinguishable, though only one type could be claimed as being restricted to a particular level. The first type was a clear ice with numerous bubbles about an eighth of an inch in diameter, which, although met with farther down the shaft, was decidedly more 160 GLACIOLOGY common nearer the surface at a depth of from 1 to 2 feet below the hexagonal prismatic ice. The second and most common type was a clear ice with very few bubbles, the latter of various sizes; it forms by far the greatest amount of ice present in this portion of the lake, and is frequently traversed by the fracture planes mentioned above. A third type, occasionally met with, had bubbles of similar size and frequency to the last, but with the bubbles drawn out into tubes, although the direction from Columnar Ice - 16/12. *: 67% 2D se % fF -Ice with Fragments of Alga ; 7 f+ ¢0 9ft Bus Wr _ Ice-cemented Breccia with Fragments covered with Fungus ‘3115 Fie. 52. Section Blue Lake Trench which they had elongated was sufficiently indicated by a bulging of the tube at the bottom, so that the bubble and tube bore a strong resemblance to a thermometer. The last type observed was only in local patches about 6 inches square. In it the bubbles appear very similar to those of the last type, but are much smaller and more numerous, giving quite a lined structure to the ice. This type frequently appeared quite suddenly above perfectly clear ice. On examination Mawson found these elongated bubbles to be hexagonal in shape like negative ice crystals. In one or two cases these drawn-out bubbles ended abruptly against one of the fracture planes already noted. LAKES AT CAPE ROYDS 161 C. From 9 to 11 feet the ice contained a quantity of living alga with living roti- fers and water-bears, and frequently around the pieces of alga we could observe a circular patch of ice which was quite opaque, evidently owing to secretion of some substance from the plant. D. At 15 feet bottom was reached, consisting of a breccia of kenyte and gravel formed from this rock, together with numerous small erratics cemented by ice, and containing a considerable quantity of both living and dead alga. One fragment worthy of note was an angular piece of trachyte, coated on both sides with a layer of growing alga. This alga, when examined by Murray, yielded numerous colonies of a smaller unicellular alga with abun- dant chlorophyll, several rotifers and water-bears, and a mite. It seems that the bottom of the layer C. must be the downward limit of the effect of the summer thaw of recent years, and it must be very unusual for the thaw to extend even to that depth, for within the range of our experience there has been very little even of surface thaw at this lake, the removal of the surface of the ice being almost wholly confined to ablation of the nature of evaporation. Unless melting takes place from the bottom upwards, it must be very rare for the whole of the lake ice to be thawed, and the presence of living algze and microzoa at this depth is there- fore very interesting, for the period of suspended animation in both plants and animals must extend over many seasons. A very mild summer indeed would be necessary to cause much of the Blue Lake ice to melt, for this lake is of much greater bulk than the others of the peninsula. A factor still more potent to preserve the ice is the snow-covered nature of the slopes immediately bordering the lake. It is only locally in the shallower parts of the lake, where the insolation of the kenyte is pro- nounced, that any large amount of ice is thawed. OTHER TRENCHES IN BLUE LAKE Trench sunk in the Narrows of Blue Lake, July 20th. The ice was only 3 feet thick, and the section was as follows :— A. 3 inches of ice, with very coarse gas bubbles partially filled with powdery ice. B. 6 inches of ice, in which the bubbles were drawn out into fine capillary tubes. C. 2 feet 3 inches of very clear and compact ice, with conchoidal fracture, and apparently very pure and free from bubbles. Through all three varieties a coarsely prismatic structure was very marked, the ice being crystallised in long hexagonal prisms about half an inch in greatest trans- verse diameter, the outlines of which could be traced through the two upper types of ice, and the first 6 to 18 inches of the third type. This ice must have been the product of the freezing of last year’s thaw-water, for even in the summer 1908-9 (an exceptionally rigorous one) this portion of the lake ice was completely melted. Mawson reports that the ice at this spot is slightly saline. 162 GLACIOLOGY Temperatures. Surface. ; ‘ P ‘ : : : ) 26523: Depth—1 foot . ; ; ; é : : 5 Pally 10h ss 2feet . ; : : : ; : > — 16:02 5 SiS ageut j : : : : (bottom) — 12°5° F. Towards the close of the winter Brocklehurst sank a trench in the northern half of Blue Lake. Few details are to hand about the section, but the chief differences from the ice of the trench in the southern area seems to have been the extension of the markedly prismatic ice to 3 feet 6 inches below the surface. The ice at this spot was 20 feet thick, and underneath it was 2 feet of water. On April 3rd a small combined trench and bore, put down a short distance to the west of what was later the site of Brocklehurst’s trench, |} 3in A. gave a thickness of 2 feet 9 inches of ice, and a depth of 7 feet to the lake, which there had a gravelly bottom, that | 6.in®, B. is, at that time there was a depth of 4 feet 3 inches of water under the ice at this part of the lake. Thus between April 3rd and October 17th we have almost certain evidence that in this portion of the lake 17 feet 3 inches of ice was formed, as Brocklehurst’s shaft, completed at the latter date, was sunk in ice throughout 27ins.C¢. its whole depth of 20 feet, whereas on April 3rd there was probably a thickness there of only 2 feet 9 inches of ice. Coast Lake. Phenomena due to ablation were very marked at this lake, large quantities of algz projecting several inches above the surface, as the original surface of the ice which formerly enclosed them had been lowered by evaporation. A peculiar feature induced by the ablation Fie. 53 was the production of a secondary rippled surface on the ice. This rippled surface was, during the early summer days, before the melting of the lake, much accentuated, the thaw acting along the bottoms of the ripples far faster than it did along the ridges. A similar phenomenon on a much larger scale was very commonly seen on the Ferrar Glacier. Trenches sunk in Coast Lake. These trenches brought to light another peculiar feature about Coast Lake. As will be seen from the sections, the whole or most of the lake bottom was covered with a thick deposit of a kind of algous peat, thickest at the centre of the lake, and gradually decreasing as the outside was approached. Detailed Section of Ice. A, 18 inches of cloudy looking ice, with regular layers of bubbles at intervals of an inch to half an inch. In most of the lower layers the bubbles tended to become drawn out and thermometer shaped, a tendency that increased with the depth. The layers were less well defined and more numerous in the LAKES AT CAPE ROYDS 163 PLAN OF ROSS ISLAND. Showing system of cracks in ice due partly to contraction of uppermost layer of ice during winter cold partly to the expanding and bursting action of the subsequently frozen deeper layers of water SCALE OF LINKS 50 100 150 Ke Wee ! ! \ ! I ! ! ! ! ' \ 164 GLACIOLOGY lower few inches. This type of ice shows marked resemblance to type A. in Green Lake, and is probably produced in a similar way. . From 18 inches to 2 feet the ice was of a similar type, but yellow and malo- dorous, and again the resemblance to the section of Green Lake is to be remarked. C’. A layer 9 inches thick of a kind of algous peat, which proved on melting to be composed of numerous small fragments of decayed alga. ae copter rere pa Cee va : ss Teo ih ade ANN ieee ( FLUE ly eS =. CE EE ES be 2fe" Sts> = pI ae wi S SOD0DOHR OS X= Was ee) aya jo Fic. 55. Section of ice and algous peat at Coast Lake near Cape Royds ) D, The layer C. was followed by a thin layer of ice fairly free from alga, and containing a series of small snow-tabloids and partially ice- filled gas bubbles. This layer in its turn was succeeded by 1 foot 3 inches of regularly stratified layers of the algous peat, separated by very thin seams of fairly clean ice, and ending in a layer, about 4 inches thick, which contained rather more grit than the upper layers. The presence of this peat was explained by the abundance of living alga scattered through the ice at different levels. When sinking this trench a main crack was used as one side of the trench in order to accelerate the work. This crack had originally been an inch and a half in diameter, but had been filled, with the exception of an eighth of an inch, with ice in extremely thin vertical layers, formed evidently earlier in the autumn by condensation of the vapour from the water and salt ice beneath. The crack only extended, at the time the trench was sunk, to a depth of 18 inches; beyond that depth it had evidently been entirely filled, either by the ice from this vapour, or from the oozing up of the brine along its length. Temperatures. Air temperature Surface 1 foot 2 feet 3 feet 3 feet 10 inches. — 4:5° F. — 15*5° F. —16:0° F. —16:0° F. —15:0° F. —12;5° ¥. FOI ¢ aonfo7 | 7 oly AMV AOVUUAL ‘WIOTAVEL MONS ‘2 ‘91g AMV duuad “€ ‘S14 ATUALISVA DNIMOOT ‘SCAOU AdVO ‘AMVT ANOd ‘T ‘PMA WVIXN GLW Td LAKES AT CAPE ROYDS 165 This series of temperatures was taken at a time when there had been a sudden and considerable rise in the air temperature, and the apparent inconsistence in the temperatures respectively at 1 foot and at the surface is due to the gradual adjust- ment of the ice temperatures to the new air temperature. The slowness of heat con- duction in the lake ice is very well seen here. Other Trenches in Coast Lake. April 1st. A bore was put down in Coast Lake along the main crack which formed one side of the trench already described, but a few yards farther from the sea and as near to the centre of the lake as possible. There was 2 feet 3 inches of ice, and the depth of the lake was nearly 4 feet. Very little bottom material was obtained. It was in this bore that a bamboo was fixed a few days later, by means of which the amount of ablation from the lake surface during the next few months was measured. August 10th. A second trench was put down in Coast Lake. The section was very similar to the preceding, and the alga was struck at 1 foot 6 inches and proved for a foot. August 11th. A third trench was sunk in Coast Lake, when the algous peat was reached at 2 feet 3 inches, and again proved to be more than a foot thick. During the spring powerful ablation exposed large stretches of this algous peat deposit near the edges of the lake, so that there is reason to believe that almost the whole of the lake bottom is covered with it. The ice of Coast Lake was traversed by a series of contraction cracks, and the surface of the ice was distinctly convex in places. These cracks opened on cold nights with a sharp loud tang, something like the sound made by the cracking of a stockwhip. Mawson estimated that on June 20, 1908, the minimum amount of contraction of the ice as shown by the cracks was 10 inches in a horizontal distance of 150 yards. The contraction amount was evidently much more, but was masked by the secondary addition of ice to the walls of the cracks, derived from vapour steaming up from the water below. Round Lake. This small tarn occupies a depression between Blue Lake and Clear Lake, but is of the Green Lake and Coast Lake type. A trench was sunk in it on April 17th. At about 2 feet 3 inches we reached the bottom, and broke through a thin layer of decayed alga into the gravel beneath ; for some time before reaching this layer, however, its presence was advertised by the unpleasant smell of the gases liberated and the yellow colour of the ice. The ice all through was characterised by a streaky appearance, owing apparently to the extrusion of salt solution globules between the crystals. Temperatures. Surface ; 2 ‘ ‘ : : : : . —I15°F. Depth 6 inches. : : : ‘ é 5 . =—12° RF. 3 IL foot : : ‘ ‘ 3 : : 5 = Bem » 18inches . ; : : : : ; 5 = BS 12). py aes : : : : : : ; é (Of? IDE Air temperature . ; : ‘ : F : . 25°F: 166 GLACIOLOGY Pony Lake. This small lake, close to which our winter quarters were estab- lished at Cape Royds, measured about 9 chains by 3 chains. Its surface is about 15 feet above sea-level. The water was somewhat saline, partly through salt spray from the blizzards, partly through mineral matter dissolved out of the surrounding kenyte lava. It occupied a shallow rock basin excavated by the ice of the Great Ice Barrier. The ice of this lake showed about 1} inches of ablation between April 18, 1908, and June 12 of the same year. The whole of the ice of this lake, which is quite shallow, melted during the summer. At the time of our arrival early in February 1908 the lake surface was recently frozen over. The general appearance of Pony Lake is shown on Plate XLHI. Fig. 1. LAKES AT CAPE BARNE As the Cape Barne lake district was 2 miles or more away from our Hut at Cape Royds, detailed work was impossible during the winter. During the spring and summer also sledging preparations and sledging prevented our spending much time in scientific work near the camp, and consequently the lakes were not examined nearly as carefully as those at Cape Royds. During our few visits to Cape Barne the lakes were roughly surveyed for adding to the Plane Table Map. Most of the notes on the Cape Royds lakes would apply to those at Cape Barne, at any rate as far as superficial characteristics were concerned. The largest of these lakes were situated in roughly parallel grooves running N.N.W. to S.S.E., and were named by us Terrace Lake, Deep Lake, and Sunk Lake; the smaller circular depressions, when ice-filled at all, were occupied by small tarns. It was in one of these small tarns that our best example of the formation of a convex surface was seen. The method of formation seemed to be here as follows :— The ice expanding as it was formed was forced upwards in the centre, and thus a convex surface was produced; this was exaggerated by the formation of each successive layer, until at last the pressure on the top layers was sufficient to over- come the cohesion between the molecules, and a crack resulted. As the process continued this crack would become wider and wider, and would affect a greater thickness of ice, until, when finally the water of the lake was all frozen, the lake would be occupied by a bi-convex lens of ice with cracks, wide at the top and tapering away to nothing below. In some cases this process was modified by the cracks traversing the whole depth of the ice and tapping the water, when recement- ing of the cracks took place. This convex surface would sometimes be partially or completely removed by ablation during the winter, and a level ablation-rippled surface substituted. Terrace Lake. Terrace Lake occupies the longest valley in the Cape Barne district. It is about 700 yards long, and is almost divided into three lakes by two hard ridges of kenyte. Its surface is about 180 feet above sea-level. It is sur- LAKES AT CAPE BARNE 167 SUNK LAKE M‘Murdo Sound 18 Feet belowsea. . Showing effect of ablation in depressing the surface of the lake below Séa fevel. (oe Vis Talus Beach gravel. Kenyte ey oe ‘ 4s! e a ze i an ee ee wr e ; Sea Level. Loe iS ee : od ZY \/ Ca SSR = = Y. Wy. a ~( = ea: Y ) Nanny = A = CR aE) Vi =a eR ye iE ve j ~< —<| TS / pe Ve = Feet. Horizontal & Vertical Scale. Feet. 100 50 0 100 200 300 400 500 ee eel 30 2 0 O 50 100 150 Metres. Metres. GRAVEL. © Chiefly kenyte with 4j;., MORAINE old Camp . 3 g little greenish grey Ge WILL Loe trachyte, brown pak 388 phonolite, & fragments fe of palagonite. kenyte. iy fs ro} MIDGET TARN MS MURDO Heart L. See > SOUND m NVlaiwaw 2 ae ow = Err *s a> % ayn daea Jeuwnjo gg huan J Istettahe\\. = at Scale in Chains Fa 20 10 0 10 20 30 40 50 60% ey aa uae kenyte rocky poinc # Fic. 56 168 GLACIOLOGY rounded by low debris-covered hills, and receives its name because of the well- marked vestiges of at least three terraces on the slopes of these hills. None of the terraces are very much above the present level of the lake, being only a few feet apart. The lake is fringed with a certain amount of the algous plant so common at Cape Royds, and large bunches of the same plant were weathered out of the surface by reason of the ablation of the lake ice. Before the end of August, at least 3 or 4 inches must have been removed by ablation since the preceding summer, Parts of this lake were very deep and of very pure and clear ice, and at these places the inclusions in the ice were plainly visible at a great depth. It was here that the photograph of a snow-tabloid half a foot in diameter was secured, and these snow-tabloids were very common. These tabloids were usually cavities formed by gases, in some cases perhaps set free from the alge, and partly filled with powdery ice. Many pieces of alga were visible enclosed in the ice, and above them generally were streams of small bubbles showing up clearly against the clear lake ice because they contained a quantity of finely-divided ice particles growing like an efflorescence on the inside of their ice-walls. This efflorescence in some of the larger bubbles examined seems to be due to the expulsion at low temperatures of the water-vapour taken up at high temperatures, a process which would have small result at first, but after many repetitions seems quite adequate to produce this small amount of rime. Another occurrence unusually common here was the interstratification of fairly large stretches of rippled snow between layers of ice. All those seen here seemed to be at the same level, and at 3 or 4 feet below the surface, but the estimation of depth is only approximate, for we dug no trenches in the lakes. It was near Terrace Lake that a thick deposit of dead alga of the type oceupy- ing lakes was found at a height of 40 feet above any present lake surface. It seems probable that this deposit, which was 2 or 3 feet thick, and covered with a layer several feet thick of moraine gravel, was the remains of an old lake-bottom elevated and denuded. Deep Lake. Deep Lake was bounded on its east and west sides by cliffs of highly-jointed kenyte, with the joints radiating in fan shape. To the north of the lake was the ridge which was capped by mirabilite, and to the south was a gradually shelving plain of moraine matter. The cliffs at the side dipped almost perpendicu- larly beneath the ice, and it seems probable, since we could see no bottom, although the lake was very clear, that the depth here is at least 15 or 20 feet. Its surface is about 40 feet above sea-level. This lake was one of the earliest of the fresh- water ice lakes to melt, for already before the departure of the Western Party on December 9, 1908, a fringe of water had formed at the foot of the kenyte clifts. Unfortunately the extent of the thaw was not ascertained. Sunk Lake. This lake received its name because the present surface of the ice LAKES AT CAPE BARNE 169 comprising it is 18 feet below sea-level. It measures about 176 yards by 66 yards, and is about 2 acres in extent. Its surface was very rough, and covered by a thick deposit of the prismatic or coralloidal ice, which, from the domed nature of its surface, seems to have undoubtedly been formed from the conversion to ice of the under side of snow-drifts. The presence of this prismatic ice in such large quantities renders the surface of this lake comparable with that of the southern half of Blue Lake, and in both cases it forms strong evidence that both Sunk Lake and southern Blue Lake have not been melted to any large extent for several years. In the case of Sunk Lake an additional piece of evidence in favour of a long period without melting is afforded by the presence of large blocks of kenyte half imbedded in the lake ice. Similar boulders were observed imbedded in the ice of Blue Lake. It is difficult to account for their occurrence in their present positions. In conclusion, we are indebted to Murray for a few isolated notes showing the temperatures to which some of the water of these lakes rises during the course of the summer. TEMPERATURE OF LAKE WATER Green Lake, 3rd January 1909. A : c : j . +36° F. 2nd February 1909 . ‘ : : 2 : 5 Sees 1a (It doubtless went higher, but was not visited often.) Coast Lake, 4th December 1908 . : : ‘ : : Avie whe 2nd January 1909. ; : : : F . +40° F. 18th January 1909 . : ‘ : ‘ ; . +45° BF. Round Lake, 4th December 1908 . ; : ‘ 3 ; g SEO}? 10! 10th December 1908 ; ; : ‘ F 5 SECIS INC Pond at Cape Barne, December 1908. : 2 : . . +54° F. CHAPTER VIII ICEBERGS THE first iceberg was sighted on our first voyage south in the Nimrod near lat. 63° 59’ §., long. 179° 47’ W., on January 14, 1908. It was not until the Nimrod reached the Antarctic Circle that the icebergs became actually very numerous. On this occasion, January 15th, the Nemrod encountered an extra- ordinarily vast fleet of bergs, varying in height from about 20 to 80 feet. These were met with at about 9.15 p.m., and the Nimrod continued steaming through them until 3.15 p.m. on the following day. These bergs were met with in approxi- mately lat. 66° 37’ S. and long. 179° 36’ W. It is estimated that they extended for a width of about 80 miles southerly from this latitude. The measurement of the belt in an east and west direction was not ascertained. The following is a description of this vast fleet of bergs written at the time :— “Singly at first, then in groups of twos and threes, there came into view not pack ice but great icebergs. These were of tabular shape and nearly all rectangular, mostly from 30 to 80 feet in height. Above they showed like the purest alabaster or whitest Carrara marble, shading into exquisite tints of turquoise or sapphire at the water’s edge, and changing to a pale emerald-green below the water. Gradually as the Nimrod forged her way southwards, and the bergs increased vastly in numbers, we seemed to have entered the great silent city of the Snow King, the Venice of the South. With full steam and all sail we hurried along, now down the wide waterways between the bergs, now along the narrow lanes, with a wall of ice to starboard and a wall of ice to port. The helm had frequently to be put hard up or hard down to avoid colliding with the ice. Now and again the bergs closed in so closely that there seemed no way of escape for our little ship, but always, just as we seemed to have reached a cul de sac, a fresh lead opened to our view, and the Nimrod was promptly headed into it. There was no darkness that night, and in the grey light the bergs shimmered like ghosts. As the day of the 16th wore on the bergs became lower than before, rising to heights of only from 20 to 40 feet above the water. Most of the bergs were tabular in shape, with flat, even tops, but some, especially the larger bergs, from half a mile to two miles in length, were dome-shaped, sloping gradually right down to the water’s edge, or bounded seawards by only very low cliffs. All the bergs were formed of compressed snow or névé in the portion visible above the water, and were regularly and perfectly stratified in 170 PLATE XLIV Fic. 1 | To face p. 170 ICEBERGS 171 thin layers. Towards noon on the 16th the bergs, which had lately been getting rather fewer in number, thronged thicker than ever, so that it required careful navigation to keep the ship in the leads of open water between them. At last we burst quite suddenly into an open sea, and saw the crystal city fade from our sight below the northern horizon.” These bergs, which were evidently not formed of glacier ice, but were of the nature of snow bergs above, passing into “shelf ice” beneath, were no doubt derived from King Edward VII. Land or the adjacent coast-line. They were mostly too low to have had their origin in the Great Ice Barrier. The berg in Plate XLIV. Fig. 1 appeared to be about 30 to 40 feet in height, and, as shown by the photograph, possesses long spurs. These project for a distance of from 80 to 100 feet beyond the foot of the cliff of the berg faces. This berg, like all those sighted in this vast fleet, was obviously formed in its upper portion of stratified snow. It seemed probable to us that this rested on old sea ice, and that the great spurs projecting under water from this berg were formed of the latter material. If this surmise is correct, this fleet of bergs must have been formed by the breaking out of a very large area of old sea ice laden with snow. We saw no signs of any true glacier bergs amongst the whole of this vast fleet. No trace was seen of moraine material or erratics on any of the bergs. We thought that they were probably formed for the most part from very old sea ice with many years’ accumulation of snowfall. On a larger scale they closely resemble the snow-laden ice floes formed of one season’s sea ice with its overburden of snow, which we photographed in the act of breaking out and being drifted out to sea near Cape Royds in 1908. It is, of course, possible that some of these bergs were formed of thin land ice, instead of sea ice, at the base. Apparently these bergs had been drifted from a point lying to the north of King Edward VII. Land, possibly from its northern shores. According to our present information about King Edward VII. Land, it is a large area of either closely contiguous low-lying islands, or it is a low plateau-shaped portion of the Antarctic continent proper. It is certain, at any rate, in view of the recent discoveries by Amundsen’s Expedition and the Japanese Expedition, the latter under Lieutenant Shiraze, that there is a considerable gathering ground for snow in this region. At the same time the snowfall appears to be very light; this would hinder the development of glaciers on a large scale, and would encourage the growth of old sea ice, the aggregation of which might proceed for many seasons for some distance out to sea along its northern and western shores. The old sea ice, weighted down by the burden of snow, might actually sink below sea-level, and the lower layers of snow on the berg or floe might then become saturated with sea water and alternately thawed and frozen, the net result being the growth of a berg, formed of old sea ice at the base, with a layer above that of old snow cemented by salt spray and sea water. Near the top the bergs pass into horizontal and well-stratified 172 GLACIOLOGY layers of snow. The Plate shows one of the larger of these tabular bergs of what may be termed shelf ice capped by snow. This formed one of the fleet above described. Plate XLV. Fig. 1 shows the stratified character of the snow in one of these bergs, which had become tilted as the result of differential corrosion in the sea water. The height of this last berg appeared to be about 60 feet. The older bergs not only exhibited traces of tilting, but also extensive wave-worn grooves at their base. Such a structure is well illustrated in Fig. 2 of an iceberg close to which the Nimrod passed in Ross Sea in the third week of January 1908. While the solvent action of sea water, combined with the mechanical erosive force of the waves, tends to rapidly destroy these bergs, the work of destruction is to a limited extent further accelerated by the collision of the bergs with each other during blizzards. The effect of such collision in crushing up the layers of snow and névé, of which the upper portion of the berg is formed, is illustrated in Plate XLVI. It is very noticeable that the sides of bergs facing the north become strongly etched in the warm beams of the noonday sun. In fact, for a great part of the twenty- four hours during the time of midnight sun, such faces showed evidence of more or less continued thawing. ‘The icicles dependent from this berg are clearly shown in the photograph. At the base of the berg is seen the fringe of icicles formed along the wave-worn grove. If much dust was present on the surface of bergs, the effect of thawing became more pronounced. Such cases were of course most frequent amongst bergs of blue ice derived from land glaciers. An interesting berg of this kind was sighted near Cape Bernacchi by the Northern Party. The berg was about 70 feet in height, and the face directed towards the north was beautifully fluted, the structure having some resemblance to the pipes of an organ. A close examination of this structure revealed the fact that the fluting was the work of comparatively small quantities of rock dust together with fine pebbles. In the first instance these appear to have been distributed with tolerable uniformity in a thin layer over the surface of the berg. In places more heat would be absorbed by this layer of rock material than in others, on account either of difference in the colour of the rock, or in the thickness of the layer of rock debris, and as a result small thaw hollows would be produced into which the rock dust and pebbles would glide. The thaw-water from these conical depressions, if they were situated near the northern face of the berg, would sooner or later overflow in a tiny rill, and cut down for itself a channel in the northern face of the berg, down which it would fall in tiny cascades. It would carry down with it some of the dust and small pebbles, and these, arrested in their downward progress on small projections of the ice-cliff, have further accelerated the process of thaw and completed the grooving process. The surface of this particular berg was, therefore, much pitted with typical “dust wells.” Bergs formed of true blue glacier ice were comparatively uncommon. Altogether only a few were sighted in the journey of 200 miles from Cape Royds to the PLATE XLV Eig. 1 Fic. 2 [To face p. 172 ICEBERGS AND SNOW BERGS 173 Drygalski Ice Barrier as against many snow bergs. This seems strange when one considers that an immense proportion of the west coast of Ross Sea and McMurdo Sound is occupied by piedmont ice. At the same time it must not be forgotten that this piedmont ice or shelf ice closely approximates in places to the structure of the snow bergs formed by accumulations of old snow on sea ice of many seasons’ growth. Such bergs as were formed of blue ice, and were more or less charged with rock dust and other rock debris, had probably been derived from the snouts of some of the outlet glaciers of the Antarctic, or from the foot of the piedmont. Near the final stage of their history, before they disappear, the snow bergs with their foundation of old sea ice are gradually eroded away by the mechanical force of the breaking waves, and at the same time become thawed in the rays of the sun, until at last nothing is left but what appears to be a perched block of old snow resting on a small ice island, the buoyancy of the latter being sufficient to keep the old snow of the berg still above the level of high water. Obviously the last part of such a berg to survive would be the substratum of old sea ice on which the snow mass was originally built. From what has been said, it is apparent that it might be possible to divide the ice bergs of the Antarctic regions into three classes, viz. :— 1. Snow bergs formed on a base of old sea ice. 2. Bergs formed of shelf ice. These may grow as a piedmont resting on a rock foundation forming a wide fringe of the Antarctic shore-line, or may develop like the Great Ice Barrier as a mass of glacier ice formed of the expanded fans of numerous outlet and alpine glaciers with the sea ice between them, held fast for a vast number of years, and then added to by many hundreds of years of snowfall. This latter variety of shelf ice presented by the Great Ice Barrier thus unites some of the attributes of the snow berg ice with that of the piedmont ice. Thus the shelf ice may be said to have two types, (a) the piedmont, (b) the barrier. 3. The third class of bergs are the blue bergs, with their englacial or supra- glacial morainic freight launched from the snouts of outlet or alpine glaciers. In regard to the flotation of these different types of bergs, the buoyancy of class 3 is already so well known as not to call for comment here. In regard to class 1, we observed at Cape Royds that when the sea ice was breaking out up to the tidal crack, the rectangular bergs so formed had a covering of from 6 to 8 feet of packed tough snow resting on a substratum of sea ice of one season’s growth ; the latter originally did not exceed about 7 feet in thickness, and at the time the disruption occurred had been considerably thinned and honey- combed by the thawing action of sea water. As far as we could ascertain, from 3 to 4 feet at the base was formed of honeycombed sea ice, the remaining 6 to 8 feet being hard compressed snow. About 1 mile south of our winter quarters at Cape Royds there were four stranded bergs, but it was not clear as to which of the above classes 1 and 2 they might be referred. The portion of these bergs above sea- Z 174 GLACIOLOGY level was formed of well-stratified layers of old snow. The bergs were from 78 to 80 feet in height. The interesting observation was made by Captain F. P. Evans, when sounding around these bergs towards the end of 1908, that they were aground in water 14 fathoms in depth. Thus in this case only httle more than half of the berg was submerged. This particular berg was of the typical tabular variety, bounded by almost vertical sides, and was about a quarter of a mile in length. Another and similar berg, evidently broken off from the same mass, is shown on Fig. 2 of Plate XLVI. It will be noticed that this berg, which has somewhat the shape of a massive castle wall, stands on a wide shelving platform formed by this marine erosion. The wall itself has been somewhat undermined, giving its summit a turreted outline. Icicles can be seen dependent from its overhanging portions. It will be noticed that in the photograph the part of the berg which has been most undercut is naturally that which faces the blizzard wind, that is, the right-hand side of the berg, as shown in the photograph. PLATE XLVI IDiKe,, al BSS Ines [To face p. 174 CHAPTER IX ICE-FOOT AND SEA ICE ICE-FOOT THE term ice-foot as employed by us is applied to the low cliffs formed partly of sea ice, partly of overlying snow-drift consolidated by frozen spray, which fringe the coasts of the Antarctic after the breaking away of the sea ice in summer time. These cliffs of the ice-foot are from a few feet up to as much as 70 to 80 feet in height, their usual altitude not exceeding about 20 feet above sea-level. Their existence makes landing on the Antarctic in summer time often a matter of con- siderable difficulty. As will be explained in detail presently, they are formed partly by a process of addition, partly by subtraction. As we followed carefully every phase of their development, and took a series of photographs, it is hoped that the observations will make the subject of an Antarctic ice-foot intelligible. It is proposed to describe the ice-foot, where specially studied by us in the neighbourhood of Cape Royds, in the chronological order in which our observations were made. At the time when we reached Cape Royds, at the end of January 1908, the sea ice was still fast in Backdoor Bay and near Flagstaff Point. Owing to the drifting action of the blizzard winds the surface of the sea ice had been covered with snow, which rose in the form of a gently inclined plane from the surface of the sea ice up to the tops of the low cliffs. The latter were formed of kenyte lava, and at spots where they were completely levelled up by drift were from 15 to 20 feet high. Early in February an exceptionally high tide led to a very sudden break up of the sea ice, together with the overlying snow-drifts next the shore. The general appearance of the breaking up of the fast ice on this occasion is shown in Fig. 57. The floes in the distance next the Nimrod are covered with a thickness of about 6 inches of old snow. In the foreground, where not only the sea ice but the snow-drift as well has been broken through, the floes consist of from 5 to 6 feet of sea ice formed during the winter, capped by 7 or 8 feet of hard compressed snow. This overburden of snow is sufficient to completely submerge the sea ice of the floe. The followmg sketch indicates the structure of the sea ice at that time at Cape Royds, and shows also the position of the ice-foot. The detachment of these small rectangular bergs, of sea ice below and compressed 175 176 GLACIOLOGY snow above, leave behind the vertical wall of the ice-foot. Obviously the tendency is, in rough weather, for nearly all the sea ice to break away right up to the edge of the rocky shore-line, and it is the cliff which is finally left which constitutes the ice-foot. This cliff is attacked by the sea surface below, which mechanically erodes it, as well as by the warm sea water which causes it to thaw, the combined result Cape Royds Drift, Snow tke Tide Crack _— Prismatic Sea Ice \a Vv — \ e Sea level AAT EL AS REAL GPA EG ruz . ay" EGE 5% K —— Fa oS on, Moraine : ae Fi ae ie SM ae e Se “att MN asses Ke ny’ \ LAGLS EA Tide Crack ; Ss 3 ° = Pe TT ; =i eer gv Sea /evel eee oecar nasa ec AUIS ve = — Cleese *t ny ——— ee ano Seg level \2 to ae (‘6 Pye Scale of Feet 10 20 30 40-50 SSS ee o 5 10 15 Scale of Metres being that the ice-foot cliff is hollowed out in a series of caves, or is eroded back below right to the rocky cliff face. Meanwhile thaw above removes a great deal of the superincumbent old snow-drifts. Thus, as the summer advances, the ice-foot cliff is constantly dwindling. With the heaving of the waves and rise and fall of the tide the roofs of the caverns of the ice-cliffs are subjected to a constant drip of salt water, and this forms a beautiful set of icicles. The general appearance of the ice-foot, when the thaw has advanced as late in February as the 18th, the time the photograph was taken, is shown on the second sketch. PLATE XLVII OE Se Fie. 5 | To face p. 176 PLATE XLVIII Fie. 2 4 [To face p. 176 PLATE XLIX ICE-FOOT Fic, 2. KENYTE LAVA FROM MT. EREBUS. SEA ICE WITH ICE FLOWERS [Armytage [To face p. 176 yo te | ry i - al a =. Vi ICE-FOOT 177 In this case the whole of the sea ice has been dissolved or eroded away right up to the rocky base of the cape, and all that is left of the ice-foot cliff is a mass of old snow-drift, which, undereut by the waves, and fringed with abundant icicles above, as the result of prolonged thawing of the snow-drift, has been deeply and irregularly carved, leaving an appearance of statuesque figures like those seen on Plate XLVII. Fig. 4. Plate XLVIII. Fig. 1 shows a slight modification of the previous structure. It is a view of Frontdoor Bay near Flagstaff Point, Cape Royds, taken in February 1908, and shows the overhanging ice-foot, with its surface here further consolidated and added to by incrustations of frozen spray. The particular part of the ice-foot shown has been consolidated and added to by accretions of ice derived from the freezing of sea spray. This headland faces the prevalent blizzard winds, which blow from the direction of the left of the picture, and dense sheets of spray are frequently flung over the ice-foot and across the headland. The portions of it, which escape freezing on the surface, freeze lower down, as dripping takes place, as icicles, and so produce the willow-tree pattern so characteristic of this part of the ice-cliff. From February 15th to 18th, 1908, a fierce blizzard raged, which flung vast volumes of sea spray over the cases of provisions, cloth, and other Antarctic equip- ment shown in the photograph. In places there was actually as much as 7 feet of tough fibrous ice piled up over our gear. A different type of ice-foot is shown on Plate XLIX. Fig. 1. This view is taken at Blacksand Beach, about 1 mile north of our winter quarters at Cape Royds. What was originally a shelving beach, formed of kenyte sand, has there been converted into an ice-foot, first, by the freezing of the sea ice, and subsequent drifting of snow by the blizzard wind from inland, in the form of wedge-shaped drifts, across the edge of the sea ice. Storms occurring later broke out the sea ice almost up to the edge of the gravel bank, carrying away much of the snow-drift on the loose floes. At the time when this low cliff was left heavy breakers flung the spray far and wide over this part of the shore, and built up dome-shaped masses closely resembling stalagmites, but formed, of course, of a mixture of old snow-drift and ice derived from infiltrated sea water. Immediately to the right of the two bergs in the photograph may be seen a pressure ridge of blocks of sea ice. This is formed by the pressure of a recent northerly wind on broken-out masses of glacier ice originally met with farther north. Plate XLIX. Fig. 2 shows a still later development of the ice-foot. This photo- graph was taken about March 15, 1908. It shows the overhanging ice-foot, there about 15 to 20 feet in height, with its base undercut by the action of the waves, and with icicles hanging from the roof. In the foreground are some slabs of old sea ice with portions cemented together by newer ice, the whole covered by a fine crop of ice flowers. In the background, at the top of the picture, are low cliffs about 50 to 80 feet high of black kenyte lava. Another appearance of the ice-foot taken still 178 GLACIOLOGY later in the year, in April 1908, shows in the foreground heavy snow-drift at Black- sand Beach. Above it are some small dark caverns, from the sloping entrance wall of which there hang a number of club-shaped icicles. It is difficult to understand exactly why these icicles are club-shaped, unless it be that, as sea water is a mixture of several solutions, each having a freezing-point of its own, as the result of progres- sive freezing the mineral matter contained in the original sea water becomes more and more concentrated in the residual water. As the freezing-point of these con- centrated brines is lowered, we observed that the tips of the icicles were nearly always moist and sticky unless the temperature fell below 0° F. Below that temperature they were usually dry and free from any of the brine solution unfrozen. The blizzard winds drove innumerable snowflakes before it, which impinged on the brine-tipped sticky ends of the stalactites and were arrested in their flight, and thus by degrees built up a club-shaped end to the stalactite. A similar phenomenon, but on a still more striking scale, is shown on Plate LIL. Fig. 1. This was taken in mid-winter under the overhanging eaves of the ice-foot a few feet above sea-level. It will be noticed that the icicles terminate there in feet-like forms, some resembling the hooves of horses, others human feet. We observed that the toes were always directed against the prevailing wind. Evidently these feet have been built out to windward by the action of the snow-bringing air currents from the south-east. The scale is shown by the height of the two hurricane lamps, by means of which the photograph was obtained after an exposure of 20 minutes with full aperture and special rapid plate. On Plate L. Fig. 1 some remarkable structures in ice and drift snow are shown resembling the forefeet of horses. The explanation of their origin is similar to that of the human-like feet in the previous figure. After the formation of the early sea ice in autumn, during March and April, blizzard winds, combined with rise and fall of the tide, served to break off sheets of sea ice formed at the base of the ice-foot, but as the temperature continued to fall, these broken fragments became recemented. Little by little the cliff of the ice-foot, as the winter advanced, became levelled up by snow-drift. In cases where the ice-foot was in the lee of the prevalent wind the drift snow built out a beautiful cornice like that seen in Plate LI. Fig. 1. We observed in several places that, where these snow- drifts were piled up against the ice-foot, where the latter faced the prevalent wind, the tendency of the wind was to scoop out a hollow at the foot of the snow-drift, so as to re-develop the ice-foot cliff. This groove, or fosse, is to be distinguished from the moats formed by actual thawing, where sea ice or snow is brought within the action of radiant heat emanating from dark rocks exposed to the direct rays of the sun. ‘The fosse in this case is due to a strong back eddy of the wind. Plate LI. Fig. 2 shows the appearance of a large and ancient ice-foot at the northern end of Blacksand Beach. The cliff of the ice-foot is here formed almost entirely of drift snow alternating with a considerable amount of fragments of PLATE L Fic. 1. ICE STALACTITES FORMED LIKE HORSES’ FEET Fic. 2, ICE FOOT WITH SEA ICE BREAKING UP [To face p. 178 Fic. 3 PLATE LI [ Zo face p. 178 ICE-FOOT 179 felspar and kenyte lava, forming dark and regularly stratified bands. It will be observed that a fine cornice has formed at the top of this cliff, which was between 70 and 80 feet in height. The dark bands are in part due to the finely divided rock material, which has been drifted over the surface of the snow by the blizzard winds, partly to their concentration from time to time as the result of their settling down under the influence of the thaw. On this latter explanation each dark band represents a prolonged thaw immediately preceding further accumulation of snow- drift. The amount of rock material contained in this part of the ice-foot was very considerable, the layers of broken fragments being from 3 to 4 inches in width, and placed at close intervals to one another, as shown in the sketch. It is clear that already a vast amount of rock material has been removed from this ice-foot by the launching of sea ice with superincumbent old snow and detrital rock material upon it. It is possible that in part this high cliff of the ice-foot is due to the thawing action of the sun’s rays, for it faces nearly due north. Plate LI. Fig. 3 shows the appearance of the ice-foot in spring. At this time the bulk of the sea ice had broken out from MeMurdo Sound, and had drifted north- wards. This had left behind itself shorewards an indented vertical face of sea ice capped with snow-drift. Above the position in the photo, where the figure is leaning, can be seen a mass of piled up fragments of sea ice, the relic of an old pressure ridge due to the overthrust of the sea ice by a strong northerly wind earlier in the season. This photograph brings the coast-line with its ice-cliff almost back to the point in the cycle from which we first started to constitute it in Plate XLVII. Fig. 4. An important feature in the ice-foot is the tidal crack. The average rise and fall of the tide in McMurdo Sound at Cape Royds is about 2 feet 10 inches. This is of course sufficient to fracture the sea ice close to the shore-line adjacent to the ice-foot, but in many cases the position of a tidal crack is not exactly coincident with the base of the cliff of the ice-foot, being often situated slightly on the seaward side of it. In many other instances the two are actually coincident. SUMMARY From what has been said, it may be gathered that the ice-foot of the Antarctic regions is mostly a low cliff from 10 to 20 feet in height, occasionally as much as 80_ feet high, developed most perfectly in summer time. As the cold of winter approaches the sea becomes frozen over, the ice being detached from the land only by the narrow tidal crack. The snow drifted by the blizzard winds tends to level up with gently- inclined planes of drift the steep angle formed by the meeting of rocky cliff faces or steep slopes with the surface of the sea ice. During the accumulation of the drift snow a certain amount of rock debris becomes intermixed with these snow-drifts at the foot of rocky cliffs. Further, blizzard winds and spring tides, especially in summer time, break out the sea ice with its overburden of snow-drift. Finally, the 180 GLACIOLOGY thick masses of old consolidated drift, partly cemented by frozen sea spray, are broken out at least as far inshore as the tide crack. These large dislodged blocks, containing much finely-divided rock debris, together with coarser lumps of rocks, are floated northwards into Ross Sea, and driven by the south-easterly blizzards towards Cape Adare, or even farther northwards. Sooner or later they part as they thaw with their burden of rock debris, which, as already stated, is largely formed of angular fragments of fresh felspars. Thus such fragments are evidently being scattered far and wide over Ross Sea, where they must become intermixed in the bottom deposits of that sea with diatomaceous and sponge spicule ooze. In regard to the accumulation of drift snow on the ice-foot at Cape Royds, we observed that a few drifts began to form over the sea ice after its freezing during April, but it was not until the wind and snowfall on June 25, 26, 27, and 28 that these snow-drifts reached any great thickness. By the latter of these dates the drifts had become several feet in depth, and by July 10 were on a level with the top of the ice-foot of the preceding season, and where this ice-foot was lower had even begun to overflow it. Two or three days later the tide cracks had burst right through these drifts. SEA ICE If again the chronological order of our experiences be followed, we may pass to the description of Plate XLVII. Fig. 3. This represents dense screwed pack ice with a large berg frozen into it. We sighted this during our second attempt to reach King Edward VI. Land in January 1908. This pack appeared to be certainly of more than one season’s growth, and the interspaces between the crushed masses of ice are filled in with old snow. The pack proved to be far too heavy to admit of its being penetrated by the Nimrod. The berg shown has probably broken off from the Great Ice Barrier. Plate XLVII. Fig. 2 shows the fast ice, against which the Némrod can be seen pressing in the middle distance: to her right are fragments of the drift pack. This photograph was taken in December 1908. The foreground is a hill of kenyte lava, in the neighbourhood of Cape Royds. Plate XLVIII. Fig. 2 shows the Nimrod forcing her way about the same time of the year along the narrow lane in the fast ice. A pressure ridge of sea ice can be seen just in advance of her bows. Plate LI. Fig. 3 shows the appearance of large masses of floe ice in the neigh- bourhood of Granite Harbour as seen in December 1908. These floes are covered to a depth of several inches with soft snow. About this time of the year the sea ice was becoming much honeycombed, and the thickness varied from a few feet up to about 5 feet. Plate LII. Fig. 2 shows brash ice formed from the complete shattering of floe ice after a blizzard in McMurdo Sound. As the summer blizzards often brought PLATE LI [Zo face p. 180 SEA ICE 181 with them considerable fall of temperature, they helped to reunite these shattered fragments through freezing the interstitial strips and patches of open water. Plate LIII. Fig. 2 shows the appearance of the sea in McMurdo Sound near Hut Point at the end of February 1909. Pancake Ice (eierkuchen eis). We observed that ice of this type developed when the surface of the sea was being gently rippled by the wind during a comparatively low temperature. At first the sea presented a soupy appearance. On the first occasion which we saw this (on February 18, 1908) we thought, as it had been immediately preceded by a very heavy three days’ blizzard, that this soupy appear- ance was due to large quantities of partly water-logged drift snow. This idea subsequently proved to be incorrect. The pancake ice shown on Plate LIII. Fig. 2 developed gradually out of countless ice crystals, which on this occasion also imparted a distinct soupy appearance to the sea. It might also be likened to the aspect of melted paraffin wax floating on the water. Little by little these crystals of sea ice felted themselves together into small cakes, which, jostled by the gentle breezes, continually collided along their growing edges. The latter, being very flexible, become gradually turned up so as to form raised rims, and the whole pancake became slightly saucer-shaped. , Plate LIV. Fig. 1, photographed by Brocklehurst, illustrates the growth of pancake ice at about the same period. Plate LITT. Fig. 3 shows the appearance of the wake of the Nimrod as she cut her way through the pancake ice about March 6, 1909. At the time the pancakes were beginning to be more or less firmly cemented at their edges, and thus made a tough surface, which seriously handicapped the Nimrod, and for several hours held her up completely. In time the whole of the interstitial water between the pancakes freezes, thus producing a continuous firm surface of ice. If this ice lasts for the whole of the winter and following spring it forms an excellent surface for sledging; the raised rims of original pancakes, by this time rounded off through evaporation, much reduce the friction of the runners of the sledge on the ice. Plate VII. Fig. 2 shows the appearance presented by the sea ice formed in very calm and quiet water. This photo was taken on March 20, 1908. The temperature at the time these crystals grew was about —10° F. The ice flowers tasted very salt and bitter. A few days later the temperature rose to about +5° to +8°F., and the centres of the ice flowers rapidly disappeared, forming tiny briny pools ; these were surrounded with a fringe of the outer ends of the petals of the ice flowers. These outer petals or extremities of the crystal plates of ice were evidently formed of freshwater ice of the nature of hoar frost collected from the moisture in the air. Their thaw point was evidently near to 32° F., whereas that of the crystals containing the strong brines was probably close to 0° F. Evidently the centres of these ice flowers are formed of the residual brines squeezed out of the gradually congealing sea ice when it ecrystallises in calm cold weather. The » 2A 182 GLACIOLOGY appearance of the brine pools formed through the thawing of the centres of the ice flowers surrounded by their fringe of ice plates is shown on the accompanying sketch. In regard to the history of the curdling over of McMurdo Sound with ice and its final congelation, it may be stated that the surface of the ice first became crusted over during the early days of March. This ice attained a thickness of from 9 to 10 inches when it was broken up and removed by a blizzard. It was on this occasion that the ice flowers just described were formed. The next sheet attained a thickness of 18 inches, when it was broken up by a northerly swell, and removed by a southerly gale at the beginning of April, with the exception of a small patch at the extreme north of Backdoor Bay. On April 2 a fresh sheet of ice began to form, again accompanied by ice flowers. The fragments of ice that had been driven out at the beginning of April now became recemented, as shown in the accompanying photograph, Plate LIV. Fig. 2. A few days later McMurdo Sound was permanently frozen over for the winter. Scale of Inches Nevertheless, from time to time, during blizzards, large areas of ice broke out from near Cape Royds and towards the centre of McMurdo Sound, leaving a long wide tongue of dark open water extending several miles south of Cape Royds towards the ‘‘pinnacled ice” in the direction of Mount Discovery. At the beginning of July the thickness of the ice, measured at a crack extending from Flagstaff Point to the stranded berg, and about 400 yards distant from the point, was 4 feet. The thick- ness of the sea ice at the dredging ground in Backdoor Bay at the end of July was between 4 feet 6 inches and 5 feet. On August 23 the ice at a spot very near the one just mentioned, 400 yards southerly from Flagstaff Point, was trenched for the purpose of putting down a fish trap, and proved to be 6 feet thick. At the end of September the bay ice in the extreme northern corner of Backdoor Bay proved to be 7 feet thick, the maximum measured by us, but there seems no doubt that this thickness would steadily increase until probably about the end of November. It may be mentioned that we observed that the delicate plate-like crystals, which develop ultimately into pancake if the surface of the sea at the time of their formation is rippled, or into smooth clear ice surmounted by ice flowers if the weather at the time is calm, either form at the surface or possibly at a slight depth below the surface, though there is some doubt as PLATE LIU Fic. 4 Fia. [To face p. 182 SEA ICE 183 to whether the latter phenomenon actually takes place. Certainly plate-like crystals developed considerably below the surface on a dredging line which had been left for some weeks without being used. These fine hexagonal plates were in some cases as much as 6 inches in diameter, and had formed vertically down the dredging line for a distance of several yards. When dredging off the cracks extending westwards from the Penguin Rookery at Cape Royds and southwards through Flagstaff Point numbers of these plate-like crystals were brought up by the dredge, though it is possible that they may have formed in super-cooled water upon the cordage of the dredge coming in contact with it. It should be mentioned that in this case the crystals were not attached to the netting of the dredge in the way that the ice-crystal plates were attached to the dredging line just mentioned. It was observed that if the weather was calm the felted ice crystals, which formed with temperatures falling below 28° F., became firmly adherent to one another, and the ice continually in- creased in thickness, although still plastic enough to undulate under the influence of a slight swell. If calm weather continued we observed that fibrous sea ice began to form, while the alternations of rise and fall of temperatures gave rise to a banded structure in the first few layers of the ice, as when the temperature rose the ice ceased to form, and when it fell the layer of ice thickened. As the periods of high and low temperature vary in length, so do the bands in the ice vary in thickness, the latter being from half an inch, or less, up to several inches. A similar banded appear- ance has already been noted as occurring in the ice of some of the lakes, particularly in Green Lake and Coast Lake. A similar reason to that just given has been advanced by us to account for it in the latter instance also. During the formation of the first few inches of sea ice the ice appears transparent, and seems black on account of the deep water seen through it. As the ice becomes thicker it gradually takes on a greenish tinge, and finally becomes opaque. Once the sea ice is thick enough to prevent the under side being seriously affected by changes of air tempera- ture a uniform vertical fibrous structure sets in, without the transverse lamination already described. It is in this way that all the rest of the ice is formed. During the growth of the fibrous ice salts still in solution are forced out in the form of brines, the mineral matter of which becomes more and more concentrated as the temperature falls. Such brines are partly forced back into the sea water below, partly forced up to the surface of the sea ice, where they form ice flowers, and partly remain entangled between the crystals. It is suggested that this movement of the brines together with that of the air dissolved in sea water which has been expelled on freezing helped to impart a remarkably fibrous structure to the ice. The brines extruded to the surface of the ice obviously freeze as cryohydrates. Such cryohydrates were also observed by us frozen at the tips of stalactites in caverns in the grounded bergs between Cape Royds and Cape Barne. The icicles dependent from the roofs of these caves were slightly sticky from concentrated brine at normal winter tempera- 184 GLACIOLOGY tures, and had drops of the brine dependent from their lower ends. On the occasion mentioned, the middle of June 1908, when the temperature was about — 30° F., the brine had frozen as a white enamel-like eryohydrate. During the winter we observed that horizontal stratification was imparted to the sea ice in the neighbourhood of the tide cracks by the following process :—with the rise of the tide, at a time when the sea ice was pressed hard against the shore by wind or currents, so that the sea ice was not free to rise with the tide, sea water would overflow the surface of the sea ice for some distance on the seaward side of the tide crack. This layer of water would then freeze. The process being many times repeated, a deposit of lamimated ice became superimposed upon the true sea ice. Plate LV. Fig. 3 shows the appearance of such laminated ice from near Flagstaff Point. A somewhat analogous phenomenon was observed by the Western Party. They observed in summer time that the sea ice at McMurdo Sound was traversed by pressure ridges parallel to the edge of the piedmont ice. Nearest the ice-foot numerous slabs of well-laminated ice were observed, the origin of which was probably similar to that just described. They observed that local depression of the sea ice near the tide crack probably takes place on the western side of McMurdo Sound on a large seale. Along the “ pinnacled ice” (perhaps a floating piedmont heavily loaded in places with moraine) is situated a band of ice, which is probably sea ice three or four years old. The junction line between this ice and the new ice of last year was marked by a pronounced ice-foot 2 or 3 feet high. About 1 mile to the E.S.E. of where the Western Party descended there was an area along this ice-foot extending for a distance of 2 or 3 miles of intensely blue, apparently wind-swept, ice with no snow on it whatever. They had hardly advanced more than a few steps on to it when it began to crack and bend in an alarming manner, and they realised that it was merely a thin crust of ice, which had evidently formed during the last two cloudy days over what had before been a pool of open sea water. At first they were inclined to think that they had struck a salt water pool, such as that reported by the Discovery off Cape Armitage. The latter was attributed to the thawing of a swift current of relatively warm sea water flowing over a shoal; but in this case, on testing the ice in several places with ice axes, they found that there was a thin upper skin of ice on top followed by a few inches of water below, and then apparently by a solid mass of ice of unknown thickness; at any rate sufficiently thick to resist any efforts to penetrate through it with the point of the ice axe, although they were several yards away from the edge of this belt of clear, freshly-formed ice. The water intervening between the two ice layers was nowhere more than a few inches in depth. It seems probable that, owing to the pressure from the south-east and north- west, this ice had been thrown into very long gentle undulations, of which the area described was one of the troughs, and that this trough was subsequently floated by PLATE LIV s i 4 ~ WES hy , eens = a: ae ) Ga = [Zo face p. 184 = 7 Ss 1 = ' . Bf 7 - 7 Sop? a | ane ., Oe a _ ot SEA ICE 185 sea water coming up through the tide crack.* This theory is rendered the more probable by our further observation, that at the time of the return of the Southern Supporting Party to Hut Point in November 1908 it was observed that the sea ice on which we, together with the Southern Party, had been camped a few days before, had been thrown into a series of broad undulations, with a difference of level of 2 feet between the centre of the trough and that of the centre of the nearest crest. In this case the fold was parallel to the ice-foot at the point, but there were slight evidence of tidal overflow along the ice-foot below Observation Hill. At the same time this overflow was much masked by the fact that the sea ice was for the most part there hidden from view by deep snow-drifts piled against the cliff. It may be added that the old sea ice, possibly three or four years old, forming a zone separating the “pinnacled ice” from the one-year ice, was covered with snow in summer time to a depth of from 1 foot to 18 inches, and its surface was from 3 to 4 feet above sea-level. Less than 2 feet of this, however, appears to be actually ice, and it seems probable that the whole thickness of this old sea ice is not more than from 15 to 16 feet. It would be interesting to ascertain for how long this ice would persist now that it has reached its present thickness, for every year its resistance to disrupting agencies becomes greater, and the exceptionally heavy weather of 1908 had very little effect on it. Its surface was comparable with the type which we found worst for sledging on the Great Ice Barrier itself. The older drifts were not quite sufficiently hard to bear the weight of a man, and at every step one dropped 8 or 9 inches on to a firmer surface. As explained elsewhere, the space between the two crusts was filled with coarse-grained snow powder, due to a selective action of the thaw, the grains which were left having increased in size at the expense of those which had been completely vaporised. The outer crust is evidently due to the formation of fresh drifts on an old and wind-swept surface, with its snow sastrugi a foot or 18 inches high, and also to the subsequent semi- hardening of these drifts by the snow of the previous summer. After the surface of the sea had become firmly consolidated with ice in early winter, but before the ice had acquired a thickness of more than a few feet, fracture took place along certain definite lines (often approximately parallel to the shore-line) through pressure of wind and tide, and subsequently along these fractured ridges lines of pressure ice were raised. These ridges attained a height of from 10 to 20 feet. They could be seen forming chiefly during northerly winds, which forced the sea ice past Cape Royds, and piled up the ice blocks particularly high between Blacksand Beach and Flagstaff Point. The formation of these pressure ridges was a fine spectacle. While the northerly wind was blowing, as one watched from the shore one saw roll after roll of sea ice forming one behind the other, as the whole mass was steadily pressed against the coast-line by an unseen but irresistible force. * Later experiences with the Scott Expedition incline me to think that this phenomenon is better explained by a flooding of the sea ice with the thaw-water from the Blue Glacier (R. E. Priestley). 186 GLACIOLOGY Every now and then the ice would give way with a loud rending noise, and large slabs would be forced over each other across even the summits of the swiftly rising ridges. Every now and then huge slabs of ice would fall over the steep sheer sides of the ridges with a tinkling sound, and would be shattered at its base. The general appearance of one of these pressure ridges, taken by moonlight in midwinter of 1908, is shown on Plate LIII. Fig. 4. An important line of fracture and pressure extended from Flagstaff Point near Cape Royds to the stranded outermost snow berg, and from there to Cape Barne. These pressure ridges were mostly not more than from 7 to 8 feet high, except where the pressure was specially centred, as at Blacksand Beach. The individual blocks of ice forming these pressure ridges were usually not more than 2 feet in thickness. After the ice became sufficiently thick to resist buckling and to fracture evenly the belt of pressure from Flagstaff Point to the stranded berg became most prominent. The width of the double pressure ridges, one behind the other, at Blacksand Beach was about 12 yards. Another type of crack, quite distinct from either tidal crack or pressure cracks due to the wind or ocean currents, was observed by us to form in the sea ice in winter time. Between July 3 and July 6 the temperature fell steadily from +3° F. on July 3 to an average of —20° F., with an occasional drop as low as —35° F. This low temperature led to a considerable contraction of the surface layers of sea ice, and the tensile limit of the ice having finally been exceeded, several cracks opened in succession with a booming noise, like that of artillery. Such cracks may be termed contraction cracks. On the occasion referred to two important cracks of this type formed, one off the Penguin Rookery, and one farther seawards just outside the edge of the pressure belt off Flagstaff Point. The subsequent history of this latter con- traction crack, which may be taken as typical of all such contraction cracks, is of some interest. The rise of temperature between July 10 and August 13 led to the expansion of the ice and the closing of the crack for the most part, but on August 14, with another fall of temperature, the crack opened again, until it was several feet wide. The sea water forming an open lane between the sides of the crack froze rapidly, forming delicate rows of crystals, recalling the comby structure of quartz crystals in quartz veins, the long axes of the ridges being at right angles to the general trend of crack, but during the night of the 15th a northerly wind sprang up, bringing with it a rise of temperature ; the resulting expansion of the sea ice ex- pended itself on the closing of the cracks, the interspaces between their walls being now crusted over by ice several inches in thickness. This thin ice yielded under pressure, and became ridged up into folds, which were later converted into over-folds, the direction of over-folding being towards the land as one would have expected, the maximum movement of expansion, of course, coming from the direction of McMurdo Sound. The general appearance of this young ice before the buckling and folding due to expansion on rise of temperature is shown on Plate LV. Fig. 1. SEA ICE 187 Although this tough young ice was fairly plastic, the over-folds eventually cracked open at their summits, as is shown on the accompanying photograph, Plate LV. Fig. 2. On August 18 and 19 the crack opened wider than ever, and the temperature remained well below — 30° F. until the 21st, when it rose suddenly to —17° F. The expansion on this occasion once more closed the crack. Once more the newly formed ice, several inches think, became buckled into folds, which became more and more steeply inclined until they passed into over-folds, which in their turn became fractured and overthrust. Finally, the western side of the crack overthrust the southern by about 30 inches along most of its length. In local patches the opposite occurred, the eastern side being overthrust over the western; in places symmetrical folds were developed. By August 22 the temperature had risen to +4° F., and the overthrust now increased to 5 feet 6 inches. The old ice was now affected by the expansion, and buckled so that the ridges were 4 feet high or more, and large blocks began to fracture and stand on end. This was the last phase in the movement of the ice in this locality until its final break-up in February 1909. BREAK UP OF THE SEA ICE The final disappearance of the sea ice in Ross Sea and McMurdo Sound is the result partly of the disrupting forces of tidal movement combined with ocean swell set up by northerly winds, partly of surface friction of the southerly and south-easterly blizzard winds, and partly of thaw. The thaw of the sea ice takes place partly above, but chiefly below. We observed that the surface of the sea ice was soft and sticky when on the northern journey to the Magnetic Pole Plateau at temperatures of about +20° F., and we found that it was extremely difficult to drag the sledges over it. We did not experience an actual thaw on the sea ice until December 15, during a blizzard. On December 16 the temperature on the Drygalski Piedmont rose to + 33° F. at about 11.15 a.m. On December 19 the surface of the sea ice was covered with a good deal of slushy snow, with, here and there, shallow pools of water: this was obviously due to thaw. It may be mentioned that, with the exception of sheltered bays, all the sea ice had gone out from the north side of the Drygalski Glacier at least as early as December 10; in fact, the dense cumulus clouds, which we saw rising from the north side of the Drygalski Barrier on December 4, probably indicated that the sea ice had gone out already by that date. On December 20 the temperature about 3 P.M. near sea-level was +34°5° F. The surface of the sea would, of course, have been thawing under these circum- stances, but there was such a large quantity of thaw-water from the inland snow and ice spreading over the sea ice, that it was hard to say where the salt thaw-water began and the fresh thaw-water ended. For example, at the foot of the Backstairs Passage Glacier there was a shallow lake spreading there over the sea ice for a 188 GLACIOLOGY length of a quarter to half a mile and width of several hundreds of yards. At the same time we could hear torrents of fresh water roaring in subglacial channels in the ice of the piedmont glacier. There can be little doubt that while a cer- tain amount of superficial thaw does take place on the surface of the sea ice in summer, by far the most important thawing takes place beneath the ice as the result of relatively warm convection currents in the sea water circulating beneath it. On our way to Cape Royds, down Ross Sea and McMurdo Sound, we took constant temperatures when on the Nimrod, and found the temperature of the sea water at the beginning of January 1908 varied from 34° F. to 28°5° F. alongside the Ross Barrier. We found the general temperature of the sea between January 23 and January 31 was about 32° F. On January 30, after a moderate blizzard, the temperature of the sea water fell to 28°5°, probably as the result of warm surface water being skimmed off by the blizzard and colder water rising from below to take its place. These temperatures are given in detail in the Meteorological Report, and refer only to the surface water. The only deep sea temperatures, those taken at the Drygalski Piedmont at a depth of 668 fathoms, gave such abnormally high results, that we suspected that they were partly in error. It is much to be hoped that future expeditions will obtain complete serial temperatures at various depths in McMurdo Sound. A point of special interest in relation to such work will be its bearing on the direction of ocean currents in the Ross Sea region. The current indicator, which our expedition established off Cape Royds, showed that normally the current there set towards the north-west. In the direction of King Edward VII. Land it has been thought by some that the current sets in a general southerly or south by west direction underneath the Great Ice Barrier. It is possible, therefore, that it circulates under the Great Ice Barrier, first flowing towards the south-west, then turning westerly, and finally emerging on the west side of Ross Island, where it has a northerly or north-westerly direction. In the neighbourhood of Captain Amundsen’s winter quarters at the Bay of Whales the Barrier is fixed, resting on the bottom, so that there can be no current setting under it just at this spot. Immediately to the south of the Bay of Whales Captain Amundsen determined the existence of a high elongated ridge of ice, 1100 feet above sea-level, and stretching 30 miles north and south. This is at the exact spot where Ross reported the appearance of land in 1839-40. In Amundsen’s opinion there can be no question that this long ridge of high ice is underlaid by solid rock. Our colleague, Mr. James Murray, is of opinion that there were indications of a permanent current setting south past Cape Bird towards Cape Royds.* He relates that on March 16, 1908, a quantity of fine broken ice, which was being drifted northerly by a strong southerly wind, was checked on its northerly course by what must have been a strong ocean current, which he thinks came from the north-east. This south-easterly current he assumes to be part of a diverted * Heart of Antarctic, vol. ii. pp. 372-5. PLATE LV [ To face p. 188 CONTROLLING FACTORS OF CIRCULATION IN ROSS SEA 189 current normally setting from Cape Bird towards Cape Royds, that is, setting southwards. There can be little doubt that the powerful blizzard winds which control the water circulation on the west side of Ross Sea and McMurdo Sound tend to force the water northwards along the shore of South Victoria Land from Cape Royds towards Cape Adare. The easterly winds experienced by Captain Amundsen at the Bay of Whales would obviously tend to drive the water of Ross Sea from the direc- tion of King Edward VII. Land towards Ross Island. One may conclude, therefore, that as the result of the action of these two strong prevalent winds, of which the southerly and south-easterly blizzards characteristic of the Ross Island region are the more powerful, is to cause a clockwise circulation in the waters of Ross Sea.* This satisfactorily accounts for our observed directions of ocean current at Cape Royds, viz. towards the north-west. One would expect from such a circulation, if the deep-seated circulation be similar to the surface, that the warmer water would be drawn down the eastern side of Ross Sea, and that it would exert its greatest influence in thawing the sea ice in that region, and would be somewhat lowered in temperature after passing under the Barrier, and emerging perhaps in part east of Cape Crozier, in part in McMurdo Sound. Cn its northerly course it would be further chilled by the strong plateau wind blowing from the west off the high plateau on to the western waters of Ross Sea. Thus these western winds contribute another component to control the general surface circulation of Ross Sea. One would expect therefore, theoretically, that the maximum thaw effect exerted by the sea water would be on the eastern side of Ross Sea. The recent observations of Captain Amundsen are not inconsistent with this view. He found that to the north of his winter quarters at the Bay of Whales the sea was constantly open, as indicated by the rising of heavy cumulus clouds and strong water blink actually within about 8 miles of his camp. This open water persisted throughout the whole of the winter. At Cape Royds we were unable during the months of winter darkness to decide whether or not there was open water between us and the mountains of South Victoria Land to the west. Occasional moonlight enabled us to see that apparently the whole of McMurdo Sound during a considerable part of the winter was completely frozen over. This suggests that the sea water temperature here is probably lower than it is near the Bay of Whales. That the greater persistence of sea ice in McMurdo Sound as compared with Ross Sea near the Bay of Whales is due rather to difference of temperature of sea water than to that of surface air temperature is rendered probable by the consideration that Captain Amundsen found that at the Bay of Whales, even with 8 miles of this constant open water, the main air tempera- ture at the surface was often lower than it was for the corresponding period at Cape Evans on Ross Island. So far, therefore, as surface air temperatures are concerned, * A similar clockwise rotation on the whole dominates the circulation of the water in the Weddell Sea. 2B 190 GLACIOLOGY this would tend to reverse the actual conditions of the sea ice respectively in McMurdo Sound and near the Bay of Whales. Obviously what is now urgently needed is a series of current observations at various depths from the surface to the bottom of Ross Sea taken systematically at frequent intervals. It should be noted that we observed on our ascent of Erebus that the surface of Ross Sea in March froze over earliest under the western mountains, from which one could see from day to day long tongues of ice spreading from the shore far out into McMurdo Sound. After our subsequent experience of the strong cold plateau winds which blow down the gaps in these ranges, especially at night time, we venture to suggest that the very strongly indented shape of the growing ice sheet in this region was due to corresponding tongues of cold air protruded from the outlet glacier valleys allowing these cold air masses to descend from the inland plateau. Obviously this cold plateau wind and the proximity of such high land as the west coast of Ross Sea accounts for this part of the sea freezing over first. That these ocean currents have a powerful influence in thawing the sea ice was obvious from the slightly honeycombed character of the ice in McMurdo Sound in January and February of 1908. In landing our stores over the bay ice at Cape Royds we frequently came upon what may be termed corrosion hollows, with only a very thin covering of ice over them. These of course were not in any way to be confounded with the seal holes. The fact that the Nimrod was able to make some little progress in hammering her way through the ice late in January shows that it must have been immensely weakened as compared with the strength it must have possessed when it was a compact sheet of ice 7 to 8 feet in thickness, asin the autumn. It is not of course certain that the whole of Ross Sea is frozen over during the winter. It is certain that it freezes over, and is continuously covered with ice for many miles eastwards from the coast of South Victoria Land, but no attempt having as yet been made by any ship to penetrate the north-east part of Ross Sea during winter, one cannot predict what its exact state is during that time of the year. MECHANICAL DISRUPTION OF THE ICE On September 1 we observed a strong water sky with cumulus cloud over McMurdo Sound, both clear indications of open water. The general appearance of the ice-foot near Blacksand Beach and of the open water is shown on Plate LI. Fig. 3. On the right-hand side is the pressure mound of ice slabs formed in the preceding autumn. At the time when the Northern Party left Cape Royds on October 5 there was already a long strip of open water in McMurdo Sound extending to within about 5 or 6 miles of the pinnacled ice, so that it was necessary for the party to make MECHANICAL DISRUPTION OF THE SEA ICE 191 a considerable southern detour in order to avoid it. By the time that the party reached the Drygalski Ice Tongue on November 29 long lanes of open sea were spreading shorewards, deeply indenting the sea ice, and threatening to bring about its entire disruption. By the time the party reached the surface of the Larsen Glacier on Christmas Day it was seen that the whole of this sea ice had broken away. At the time when the Western Party left Cape Royds in November 1908 a slight glazing was noticeable on the northern faces of the snow-drifts on the sea ice, and the sea ice just west of the Penguin Rookery at Cape Royds, particularly where it was discoloured by a large amount of finely powdered guano swept off the rookery by the spring blizzards, showed signs of rottenness. This thawing was further encouraged perhaps by heat radiated from the black cliffs of kenyte rock. From December 1, 1908, to January 24, 1909, we have no complete record of the disintegration of the fast ice. Certainly heavy pack prevented access to Cape Royds early in January, for the Nimrod on January 1 was held up in the pack at Beaufort Island, and was unable to reach Cape Royds until January 5. On January 7 she started away again to look for a lost party, and in a few hours she was again jammed in the pack and nearly driven ashore at Horseshoe Bay. She remained fixed in the pack till January 15, and was drifted across the Sound until almost within sight of Granite Harbour. On January 24 the Nimrod picked up the Western Party, who noticed that all the sea ice north of a line from the Chinese wall of the Cape Barne Glacier, and passing westwards about a mile north of the north end of Inaccessible Island, had gone out. By January 27 all the ice north of Inaccessible Island had been removed, with the exception of that between Mickle Island, the stranded berg, and Flagstaff Point, as well as a narrow fringe along the coast to Cape Barne. This last was rapidly breaking up. Where facing a large expanse of open water the fast ice usually broke off as long strips with a certain amount of brash ice between. At Backdoor Bay the first stage of disruption manifested itself as a long crack roughly parallel with the line of open water. The strip of ice between this crack and the open water became later divided by a series of transverse cracks into squarish blocks, and these gradually floated out under the influence of the ebb tide, until they were caught by a surface current and southerly wind and carried round Flagstaff Point northwards to join the main pack. As the thicker and older bay ice was approached the disrupted squares became smaller and smaller, until finally, on February 7, the thickest ice, covered with snow-drifts, broke into almost cubical blocks and was removed, leaving the bare ice-foot. It was remarkable that the blocks of this snow-covered ice frequently had projecting edges 1 or 2 feet wide, either of snow alone or of ice alone. These were due to the fracture being stepped instead of simply vertical, the line of fracture following for a certain distance horizontally the junction line between the snow-drift and the sea ice. 192 GLACIOLOGY SUMMARY This completes the cycle in the history of this sea ice. It may be noted that the sea ice is important, both as a geological and meteorological factor, by covering over with a thick, non-conducting layer the relatively warmer surface of the sea itself. The immediate effect of its formation is to greatly lower local temperatures ; when- ever, as the result of a blizzard wind, the freshly-formed ice was disrupted and driven out temperatures at once rose at Cape Royds. The geological importance of sea ice appeared to us to be generally the following :— 1. During the autumn, winter, and early spring it exerts a protective influence on the shore-line as it checks marine erosion, but when later it becomes broken up, the drifting floes grounding along the coast accomplish a very limited amount of mechanical erosion. 2. Biologically this action is important, as it checks the development of a true shallow water littoral fauna, and accounts for the absence of the shelly beaches so common in temperate and tropical latitudes. 3. It forms a gathering ground for a considerable amount of drift snow, blown off the inland ice fields of the Great Ice Barrier. 4. When broken up the floes bear out with them northwards vast quantities of finely divided wind-blown rock debris, together with occasional larger blocks which have fallen from rock cliffs. By transporting these fragments some distance from the shore seawards, the sea ice, when it melts, sheds a very large quantity of angular rock material, remarkably free from decomposition, on to the marine organic muds of Ross Sea and the adjacent southern ocean. PLATE LVI Fic. 1, FROZEN SEA SPRAY ENCRUSTING Fic. 2. DIGGING OUT STORES AFTER THE CASES HAD BEEN BOXES OF STORES BURIED IN ICE DURING A BLIZZARD Cape Royds after the blizzard of February 19-21, 1908. Inleft top corner are the snow bergs aground in 14 fathoms, with Cape Barne in the distance Fic, 3. VIEW OF HIGH HILL, CAPE ROYDS, WITH CAPE BARNE ON THE LEFT IN THE Fic. 4. KENYTE LAVA, SHOWING SPHE- DISTANCE ROIDAL WEATHERING, NEAR THE PEN- Showing the effect of insolation in summer in ablating GUIN ROOKERY, CAPE ROYDS the snow from the surface of the dark kenyte lavas of Mount Erebus [To face p. 192 CHAPTER X WEATHERING—DENUDATION— EROSION WEATHERING 1. Due to Evaporation. Ablation, in the sense of loss of volume through evaporation, sublimation, &c., has already been discussed in Chapter II., but some notes may here be given as to the weathering effects which may result from it. The effect of ablation on salt water ice was well seen in the case of the sea spray which had been heaped over our cases by the great blizzard of February 19-21, 1908. About a month afterwards an attempt was made to recover a case of bottled beer and four volumes of the Challenger Reports, and after digging down 3 or 4 feet the search was abandoned. In February 1909 the ice had s0 far ablated that the site of this trench was only just discernible, and when a trench was sunk for another 18 inches within 2 feet of the former one the Challenger volumes were recovered. Thus between 3 and 4 feet of this ice had been removed in the twelve months just past.* One more effect of the ablation is worthy of comment. The prismatic ice of the southern half of Blue Lake (where it was especially prevalent) evaporated very rapidly, and the evaporation proceeded much more rapidly down the opaque partitions between the crystals than down the crystals themselves, so that they remained standing apart as individual hexagons. 2. Due to Change of Temperature. Cape Royds is so littered with morainic debris that it is impossible to tell with any degree of accuracy how important a factor in the breaking up of rock is differential contraction and expansion, the result of sudden changes of temperature. That this agent of weathering is im- portant, however, can be easily seen. After one of the sudden variations of temperature, which were very common at the cape, it was quite a usual thing to find the drifts at the foot of cliffs sparsely covered with flakes of freshly exfoliated rock fragments. Screes were not nearly as common at Cape Royds as at Cape Barne, but * Mention should be made of the fact that this ice formed from the freezing of the sea spray was not dense ice, but more or less fibrous, with numerous air spaces. The removal of this 3 to 4 feet from its surface was due no doubt in part to sublimation and in part to thaw. It would of course, by reason of its salinity, thaw more rapidly than fresh water ice. 193 194 GENERAL GEOLOGY when these did occur, they gave one some idea of the amount of rock flaked off by the frost-action. Mount Cis, the small parasitic cone on the lower slopes of Erebus, was flanked on one side by such a scree, and the essentially angular nature of the fragments, together with the fact that they were all of the one very local type of rock, precluded the possibility of the debris being of glacial origin. The highly jointed nature of the lavas at Cape Royds greatly accelerates and facilitates this action, and Flagstaff Point in particular is seamed by huge cracks, and it is always possible, and even probable, that at no very distant date the western half of this cliff may fall into the sea bodily, for there is one crack extending nearly north and south which is in places 3 or 4 inches wide, and in one place it was impossible to touch the bottom of the open part with the end of a 10 feet bamboo pole. The reason for the disappearance of glacial grooves and strize at Cape Royds, and indeed from the surfaces of all the land-moraines we visited in Antarctica, is probably largely explained by this frost-weathering. Almost all of the boulders which have their striated surface exposed must have this surface flaked off, owing to differential expansion and contraction resulting in a type of concentric weather- ing. Many of the holocrystalline boulders at Cape Royds were surrounded with these arc-shaped flakes. Thus the absence of striation on the surfaces of the blocks of the moraines at Cape Royds is amply accounted for, and it is only in places from which the ice has recently retreated, or on the under surfaces of partly embedded blocks, that we are likely to find a large proportion of striated material. The survival of striated roches moutonnées, and of striated blocks, in temperate and tropical regions which have been strongly glaciated in former eras, may perhaps be in part explained by the fact that, once the period of maximum glaciation is over, the region from which the ice has retreated is only subjected to the rapid disintegrating processes of frost-weathering for a comparatively short time. Another fact which may account for a large number of blocks retaining their striated surface in old glacial deposits is that they are often enclosed in stiff boulder clay, which would exercise a preservative influence on the rocks. It follows from the facts observed, in the region of the Antarctic explored by ourselves, that the only three places where it is likely that striated boulders and rock surfaces should appear in and under the deposits of the present geological period are, (i) on the bed of the Ross Sea, where the material is protected from the action of the frost by the water; (ii) in the deposits at the mouths of the larger glaciers, where the fine sediment brought down by the thaw on the glacier accumulates and pro- tects the boulders; and (iii) in the upper portions of the glacial valleys of the main- land, which are not likely to be exposed to sub-aerial denudation until the very end of the Polar glacial period. Impressive evidences of the effect of frost-weathering are to be seen in the Ferrar Glacier Valley. Against all the cliffs bordering the glacier, except those from which the debris PLATE LVII INCHES CENTIMETERS Fie. 1, WEATHERED BOULDER OF KENYTE FROM MORAINE AT CAPE ROYDS The boulder was originally nearly round and of the full diameter of its base, on part of which itis resting. The rest of the boulder has been removed by weathering ia a eee Fic. 2. WEATHERED BOULDER OF KENYTE ON FOOT- Fie. 3. WEATHERED CONCRETIONS OUT OF THE BEACON HILLS OF MOUNT EREBUS, NEAR CAPE BARNE SANDSTONE, FROM SCREE, KNOB HEAD MOUNTAIN, Boulder about 7 feet in diameter FERRAR GLACIER VALLEY [ To face D. 194 it wa = 4 nell 7 ad - aul : 7 - : 4 ; so a 7 _ ; ae Z ° ~ f* 7 ) : 7 a . a o = - we * 7 re " _ a. 7 yi Oe | _ : - ; > _ ". DENUDATION 195 fell directly on the moving ice face, high screes of detritus were piled. These screes in some cases must have reached two or three thousand feet in height, and practi- cally the whole of the material of the upper portion of them must have been derived from the frost-weathering of the cliff faces, for in such situations the action of torrential water must be negligible. The lower portions of these screes contain large quantities of rock which cannot have been derived from the cliffs above them, and must be the material which formed the lateral moraine of the glacier at a former more extensive phase of glaciation. A phenomenon due to sudden change of temperature was observed during our stay at the Christmas Camp below Knob Head Mountain. During the whole of the stay we met there a very cold breeze, the overflow of the heavy air from the inland plateau, which was blowing over the ice in the neighbourhood of the tent. In the evening we usually lost the sun about half-past nine, and immediately the shadow of the mountain swept across the ice near us the ice was suddenly cooled by the wind, and repeated sounds of sharp cracking would be heard, the cracks taking the form of minute strain lines in the surface of the ice. This action was much more marked in the case of the thin layer of ice covering the boulder holes containing thaw-water, for these layers immediately contracted with reports like a succession of pistol-shots, and sometimes broke up altogether and flew out in all directions, making a noise like breaking glass. 3. Due to Wind Weathering. The effect of the sand-blast action on different types of rock was very well seen at Cape Royds, covered as the peninsula was with large and small erratic boulders of almost every description and texture. In the kenyte the porphyritic anorthoclase felspars were more resistant than the ground mass, and stood out all over the rock like iron studs in old-fashioned doors. The wind weather- ing of the kenyte will be more fully described in the Cape Barne section, for it was at the latter place that the best local boulder was seen and photographed. Plate LVII. Fig. 1 shows a piece of kenyte, a third of which was embedded in the ground, and protected by the gravel covering it, so that the weathered portion is standing on a natural pedestal. The contrast between this pedestal and the rest of the block gives one a very good idea of the way the felspars stand out in the wind- carved surface, and when it is realised that practically the whole of the exposed kenyte surface is of this description, the roughness of the country can be fairly well gauged. When there were any lines of weakness in the boulder, for instance, lines of flow in eruptive rocks, or lines of stratification in the Beacon Sandstone, the sand worked much more quickly along these lines, and the rocks were given the appearance shown in the second figure. One specimen of variolitic basalt was reduced to a rim of rock half an inch thick, enclosing a space, about four inches by three, occupied by a series of round balls about three-eights of an inch in diameter, and almost completely weathered out, so that the individual varioles might have been broken off by the 196 GENERAL GEOLOGY hand. One type which was sufficiently common to deserve notice was a basalt with much altered olivines and strongly cleaved augites. Both these minerals, being apparently easily disintegrated, had disappeared almost entirely from the surface of the rock, leaving what was apparently a homogeneous basalt full of small pits. Lastly, the kenyte tuffs with a soft ground mass had in some cases had this ground mass removed so much that numbers of the kenyte fragments might be seen lying loose around the tuff blocks, and only to be recognised as having been originally part of the block by the presence of a little of the cementing material still adhering to their leeward sides. The power of this type of sub-aerial denudation must be greatly added to at Cape Royds and Cape Barne—in fact at any place where the country rock is kenyte— by the quantity of small undecomposed fragments of felspar that are lying amongst the debris. The anorthoclase felspars of the kenyte are liberated in immense numbers by the weathering of the rock, and they are liberated in an undecomposed state owing to the excess of mechanical disintegration over chemical alteration. This excess is mainly due to the absence of much water denudation. These felspars, owing to their perfect cleavage, are easily broken up into small pieces, and are carried by the wind against the face of other rocks, every fragment acting as a small but sharp chisel. When these felspars, for instance, are hurled hard against any obstacle, the resistance does not cause a blunting of the point so much as a splitting into smaller cleavage masses, thus doubling or trebling the number of sharp points. The presence of these immense numbers of undecomposed felspars, large quantities of which are carried out to sea as fine dust, and similar large quantities removed in larger pieces by the floe-ice and ice-foot bordering the coast, must be having a marked effect on the beds at present forming under the Ross Sea, and partially decomposed sub-angular and angular pieces of felspar will be an important factor in the rocks which these beds will form when finally consolidated.* Another way in which the winds are playing an important part in the denuda- tion of Ross Island is presented when we consider the quantity of fine material which must annually be deposited in the Ross Sea, having been removed by winds from the peninsula. We have already mentioned in our notes on ablation how, towards the end of October, the whole of the sea ice beyond Cape Barne became dirty with sediment ; and all that material must have been deposited in the sea when the ice melted. The fine dust from Cape Royds, and a good deal of fairly coarse material too, must be removed straight into the sea to the north. It is necessary that we should not give the idea that the size of the individual grains removed in this way are all microscopic. By far the greater proportion of the grains are very * It is well known that undecomposed felspar fragments are very characteristic in the glacial sandstones of Cambrian age in South Australia, as well as in the Permo-Carboniferous glacial sand- stones and tillites of India and Australia. WIND WEATHERING 197 small it is true, but many of them, on the contrary, are quite large. Several members of the Expedition were struck quite heavy blows by the gravel carried from the ridge behind the Hut during some of the blizzards, and pieces up to an inch or more in diameter have been found on the fast ice at distances from the cliffs, which they could have traversed in no other way. A local effect, but one which must have an appreciable effect off the great rookeries, is the removal of the fine guano dust by the powerful blizzards of the spring. The long ablation during the winter and autumn had caused the accumula- tion of a lot of loose dust on the Cape Royds Rookery by the end of the winter of 1908, and the first spring blizzard removed the majority of this. There may have been some slight difference in the direction of this wind, which might account for its removing so much of the material which had apparently been almost untouched by previous blizzards, but whatever the cause, the effect was very obvious. The whole of the drifts to the north of the rookery were coloured a deep brown, the fast ice of the Sound was discoloured until it came to an end at Blacksand Beach, large quantities of the dust must have been carried right out to sea, while behind every projection along the coast the snow-drifts were discoloured, and it was impossible to get away from the unpleasant, penetrating smell of the guano any- where to the north or north-west of the rookery. In the Ferrar Glacier Valley denudation by wind was not so common as at Cape Royds, but locally it was very active, owing to the influence of the plateau winds. The reason for its influence being less in this valley is not so much that the winds are less, as that the amount of fine gravel which would be used as an agent of friction is insignificant. Such material as is carried on to the surface of the glacier by the winds is either removed by the thaw into the streams, which in their turn carry it to the entrance of the valleys, or is swept by the wind into the channels of the super-glacial streams and lodges there, or perhaps, if left long on the surface of the ice, becomes embedded there, and finally disappears beneath the surface. A limited amount of wind-weathering shows in some of the boulders of the moraines, and where it does occur the weathered surfaces all point up the glacier, so that evidently the strongest and most common winds here met with are those which are caused by the downward overflow of the cold air from the plateau. It was in the gully between Knob Head and Terracotta Mountain that the most striking instances of weathering of the sand-blast type were to be seen. One was the occurrence of numerous cups of sandstone beautifully polished and concentrically striated on the outside and hollowed out more or less perfectly inside, ranging in size from that of a cocoanut to that of an ordinary glass marble. (See Plate LVII. Fig. 3.) We were for some time puzzled to account for the origin of these “ pot- holes,” as we named them, but the mystery was cleared up when a block of weathered sandstone was found which proved to be full of rounded patches, anything up to }a foot in diameter, which were of a different colour and consistency to the 2C 198 GENERAL GEOLOGY rest of the rock. Several of these round nodules had weathered out and were lying at different distances from the parent rock, and when one or two of them were collected, and broken across the middle with a hammer, they were seen to consist of a very hard and indurated outer shell from an } to a 4 inch thick, enclosing a dark-green ferruginous-looking sandstone of larger grain, and with less cohesion between the grains. The mode of origin of these pot-holes was now clear, for they were to be seen in all stages of formation, from the nodule which was left intact and only polished on the outside, through the various intermediate stages, to the perfect cup, where the inside had been completely cleaned out, and only the outer polished shell was left, containing many of the quartz grains which had been used by the wind as files to get rid of the less resistant portion of the stone. Even a further stage was to be seen, for in time the outer shell itself began to wear away, and the cup became sufficiently light to be moved by the wind, and many had been lifted up and smashed to pieces. One other testimony to the power of the plateau wind as a denuding agent was well shown, at a height of 6000 feet, on the Terracotta Mountain, where the talus became sufficiently thin to allow the Beacon Sandstone to be seen im situ. One of the beds of sandstone was a fine-grained white rock, and this stood out in ledges 18 or 20 inches wide, and the underside of these ledges had been weathered into a series of thin, roughly hexagonal columns from 1 to 9 inches long, and from } to 3 an inch thick. Where these columns hung close together their original structure seemed, as before mentioned, to be hexagonal, and it appears probable that the weathering has been assisted in producing this particular result by some secondary structure due to alteration and secondary crystallisation in the rock itself. When the columns hung farther apart, owing to the gaps made by the entire removal of some, they had lost all definite shape, and resembled nothing so much as stone icicles or stalactites. 4. Due to Chemical Action. Chemical weathering plays a very subordinate part at Cape Royds, although the water around some of the large boulders in summer tasted quite strongly of magnesium. This type of weathering is much more developed in the western mountains, and it seems probable from the small part it plays here that the kenyte is not so easily decomposed as other rocks of the region. One phenomenon, which would lead one to an erroneous view of the importance of this agency, is the presence of an efHorescence of salts all over Cape Royds, but these salts are mostly sodium sulphate and chloride, and their common occurrence, when the removal of snow-drifts has caused concentration of the salts contained in the drift, seems to point to their having been brought originally as sodium chloride from the surface of the sea ice, so that the main chemical change that seems to be taking place in the rock material is the filching of the sulphates and their replacement by chlorides. The minerals most probably taking part in this CHEMICAL WEATHERING 199 reaction are compounds containing ferrous iron, and the most probable products will be limonite or hematite, causing the rocks to weather brown and red. It is a curious coincidence (if it is not a result of the process) that the removal of snow- drifts by ablation generally exposes a browner soil than the neighbouring perma- nently-exposed soil. Although there appears to be very little chemical weathering at Cape Royds, this is by no means the case in the districts examined by the Western Party, who explored the Ferrar Glacier Valley, where this type of weathering seems to play a much more prominent part in the denudation of present land-forms. In the moraines its effect was especially important, and was brought before our notice in three ways. The water of lakes of the Stranded Moraines, and that surrounding the boulders in the moraines of the Ferrar Glacier, tasted very strongly of magnesium, and indeed had a strong medicinal effect. The amount of salt it contained was especially noticeable in the case of many dried-up lake beds in the New Harbour Dry Valley. Where lakes had dried up owing to strong evaporation, their beds were covered with a strong efflorescence of white salt. Many boulders of the more resistant types of rock represented in these moraines were coated with a crust, in some cases an eighth of an inch thick, of carbonate of lime, and the less resistant rocks, such as many of the softer varieties of Beacon Sandstone, had had all their cement removed, and had become reduced in many cases to heaps of individual quartz grains, whilst many blocks, although retaining some semblance of their original form, crumbled to powder when struck with the haft of a hammer.* Plate LVI. Fig. 3 illustrates the effect of insolation in dissipating the ice and snow from the surface of the dark kenyte rocks of Cape Royds, and Fig. 4 of the same plate shows the general aspect of kenyte weathered spheroidally at Cape Royds. DENUDATION AND EROSION A. By Avalanches. The descent of avalanches from the steep rock slopes of the Antarctic Horst was observed by the Northern Party for a few days before Christmas in the neighbourhood of Mount Crummer. At frequent intervals daily great masses of snow would rush down with a deep thunderous roar on to the piedmont ice at the base of the mountain. Such avalanches must of course move with them a certain amount of rock material, but on the whole the denudation accomplished by this factor is probably insignificant as compared with the erosion effected by ice, running water, changes of temperature, and wind action. B. By Ice. Abundant evidence has already been quoted in support of the vast amount of erosion accomplished by ice in this region of the Antarctic. This is proved, both by the subtraction of material from the rocks of the horst, and the addition of sediments to the floor of McMurdo Sound and Ross Sea. * Frost-weathering of course contributed to make these lumps of sandstone so friable. 200 GENERAL GEOLOGY Negative forms due to erosion are valleys, both of the wide U, or alb* valley type, and of the trogtal type, hanging valleys, cirques, steps, treads, terraces, and rock basins. In the physiography of South Victoria Land the great feature above all others which arrests the eye of the observer is the extraordinarily long, straight valleys occupied by the outlet glaciers. They resemble nothing so much as vast railway cuttings 50 to 100 miles in length and 5 to 20 miles in width, their smooth sides rising from 3000 to 5000 and 6000 feet above the present level of the glaciers. Plate LVIII. illustrates a typical glacier-sculptured valley, the Ferrar Glacier Valley, showing the remarkably smooth spurless walls. Evidence has already been quoted to show the existence of alb and trogtal valleys at Granite Harbour, at the Mawson Glacier, and at the Beardmore Glacier, while there is probable evidence of a similar structure at the Ferrar Glacier. On a larger scale than typical alb valleys are the ancient spillways, through which, during the maximum glaciation, the inland ice overflowed across the great horst to Ross Sea. These are as much as 40 miles in diameter near the Drygalski Ice Barrier Tongue. The great horst has sagged downwards between Mount Nansen and the Ferrar Glacier Valley, thus allowing a vast sea of ice to overflow it bodily during the maximum glaciation. The rocks of the horst being capped by an almost horizontally bedded formation (the Beacon Sandstone) to a thickness of at least 2000 feet, facilities for observing the amount of erosion are particularly good. The lowest portions of these gaps are still occupied by glaciers which have now sunk into their trogtdler. The erosion of the rocks of the horst has been carried on to far below sea-level, at all events in the neighbourhood of the Drygalski Ice Barrier Tongue. It is of course possible to argue that the ice there, which is some 2000 feet in thickness, has simply occupied a pre-existing deep bay in the sea coast formed by tectonic subsidence. Until far more soundings than are at present available have been taken, one must admit that actual scientific measurement on this subject is somewhat lacking, but as far as the evidence goes, it shows that in the neighbourhood of the present glacier snouts the sea floor is over-deepened, shallower soundings being obtained farther out to sea than close inshore. (See sections illustrating Chapter III.) Obviously this fact is in favour of the rocks of the horst having been cut down far below sea-level by ice erosion. Another possible view of this phenomenon is that under the weight of ice, during the maximum glaciation, the whole of the land surface, including the shore- line, sank from 2000 to 3000 feet, and that the land glaciers were gradually submerged as the result of this subsidence. At present there is no proof whatever of such a subsidence having taken place, whereas there is evidence of the great horst having risen vertically, probably for fully 50 feet, in recent geological time. * Mr. T. Griffith Taylor uses the term kar terrace for the flattish floor of what we have termed the alb valley. MOUNT FERRAR A TYPICAL GLACIER SCULPTURED The Ferrar Glacier Valley, showing the remarkably smooth spurless walls. This valley is as dee) PLATE LVIIL MOUNT FERRAR KUKRI HILLS A TYPICAL GLACIER SCULPTURED VALLEY The Ferrar Glacier Valley, showing the remarkably smooth spurless walls, This valley is as deep as the Grand Cation of the Colorado, possibly deeper [To face p. 200 PLATE LVI KUKRI HILLS VALLEY p as the Grand Cajion of the Colorado, possibly deeper [To face p. 200 - EROSION BY GLACIERS 201 Cirque structure was not studied in detail, but many fine examples of cirques exist, as near Mount Chetwynd, and in the neighbourhood of the north-west side of the entrance to the Beardmore Glacier, also at the north side of the Mawson Glacier.* Hanging valleys have already been described in the Ferrar Glacier Valley in this Memoir, and fine examples could be seen in the valleys to the north of Terra Nova Bay. Steps or treads are well marked in the course of several of the outlet glaciers. Their presence can only be inferred from the existence of numerous large ice-falls, hike that to the north of the Suess Nunatak in the Mackay Glacier Valley, where a great rock-bar of quartz-dolerite crosses the valley almost at right angles. These would seem to be developed, in the outlet glaciers, chiefly at the point where the glacier ice, in course of its erosion, has reached the base of the Beacon Sandstone formation, and is recessing itself into that formation, so that it brings down its channel eventually on to the hard resistant rocks of granite, gneiss, &e. Such ice- falls were met with by Captain Scott near the head of the Ferrar Glacier Valley, above Depot Nunatak; by Sir Ernest Shackleton near the great coal-measure and limestone nunataks, Mounts Buckley, Bartlett, and Darwin. The Northern Party also observed from a distance with field-glasses that there were immense ice-falls some 30 to 40 miles inland at the head of the David Glacier, at the point where it was recessing into the Beacon Sandstone of the plateau. Terraces were observed at Ross Island, near Cape Bird, and at Backdoor Bay, as well as on the coast of Victoria Land. They are very strongly marked at Mount Crummer, and much has already been said about the shelf on which the great piedmont of the eastern side of the horst rests. The question as to what extent these terraces are due to marine erosion, glacial erosion, or the effect of running water has already been discussed. The subject of the glacial erosion of lakes has already been described in detail in the section of this work dealing with lakes, where it has been pointed out that in the neighbourhood of Cape Royds there is good evidence of rock basins having been scooped by ice action to some distance below sea-level. This is notably the ease with Sunk Lake near Cape Barne. Deep Lake, Blue Lake, Clear Lake, and Coast Lake are obviously rock basins scooped out of the solid rock by glacier ice. * A special study of cirque structure has been made by Mr. T. Griffith Taylor, of Captain R. F. Scott’s recent Antarctic Expedition, between the Mackay and Koettlitz Glacier regions, and by one of us (R. E. P.) to the north of the Reeves Piedmont. These results have partly been published in “Scott’s Last Expedition,” vol. ii., partly in the Geographical Journal for 1914. In the latter paper Mr, Taylor argues for the formation of outlet glacier valleys by cirque (ewm) erosion, obviously a possible origin. The facts should not be lost sight of (1) that the outlet valleys may be partly tectonic in origin; (2) that even if the Antarctic Horst post-dates Lower Miocene time when river erosion dominated Antarctic relief, the strip of the earth’s crust occupied by the horst may already have been somewhat notched by river valleys previous to the faulting which produced the horst. 202 GENERAL GEOLOGY C. By Weathering.—The vast importance of the denudation effected by weather- ing, brought about chiefly by evaporation, by diurnal ranges of temperature, and by wind, have already been described at the beginning of this chapter. We would here specially emphasize the enormous importance of wind in removing snow from inland seawards. The heavy cold air over the Antarctic Continent, as from time to time it rushes seawards into the great trough of the atmosphere near 62° 8. (Der Rinne, or Die Luftfurche of Hann), not only bears seawards most of the new- fallen snow, but tears out deep furrows in the old snow, thus forming the sastrugi. Near the Magnetic Pole area these sastrugi are fully 3 feet in height.* This wind erosion may very likely remove at least as much snow annually as is annually added as the result of precipitation. D. By Thaw and by Running Water.—We may now pass on to consider the phenomena of thaw and the erosion accomplished by running water. It was on November 13, at our winter quarters at Cape Royds, that the thaw was first noticed to be taking effect, when many boulders of black kenyte, which had snow in their crevices, showed large wet patches owing to the heat from the sun raising the temperature of the dark rock and melting the snow. Several large erratics of the same rock, resting on ice, or surrounded by snow-drifts, developed shallow pools around themselves the next few days, and the thaw might be said to have commenced. By the end of November the thaw had fully set in, and those drifts which had withstood the ablation of the winter and spring were fast disappearing. The thaw seemed to strike along parallel lines in the drift, resulting in sharp knife-edges of coarse-grained névé with deep depressions between, the ridges being parallel and striking upwards at a slight angle of 10° to 20° measured from the horizontal, in the one or two cases particularly noticed, towards that direction where the sun would have most power on the particular portion of the drift. Thus, a drift sheltered on the southern side, as they usually were, would have these ridges with their edges pointing towards east on the eastern side of the drift, north on the northern side, and west on the western side; probably the depressions and ridges were caused by the sun working back quicker along the bedding planes of snow charged with dust particles produced annually, or perhaps, after each blizzard season, by the concentration of the sediment in the drift. One curious feature in the thaw, partly caused by the intense blackness of the rock at Cape Royds, was that in many cases the thaw proceeded much more quickly from below the snow-drift than from above. We have trenched through a small drift, 3 or 4 feet thick, in midwinter, and found it to be snow right through to the rock, yet when it was trenched again a month after the return of the sun in the spring * Bage, Webb, and Hurley, of Dr. Mawson’s Expedition, report that in 1912-13, in their journey towards the South Magnetic Pole area, they encountered sastrugi, to the south-east of Adélie Land, quite 5 feet in height. PLATE LIX Fie. 1. LOOKING 8.8.W. FROM CAPE ROYDS ACROSS THE Fic. 2. SURFACE OF FERRAR GLACIER NOW NEARLY SNOW-FREE Sl RFACE OF KENYTE Showing the remarkable etching effect of the sun The heaviest snow-drifts are on the north-west sides of the slopes. To the on the surface snow-drifts in producing shallow right is a broad U-shaped hollow eroded by an ancestor of the Ross Barrier. sharp-edged basins, like those of siliceous sinter To left of centre on horizon is Inaccessible Island, with Tent Island at F terraces the back of it; then to the left, more distant, is Razorback Island, then Cape Barne and Cape Barne Pillar [Photo by Sir Philip Brocklehurst. Fic. 4. COAST AT CAPE BARNE Showing cliffs (of basalt) 300 feet high, the result of marine erosion Fie. 38. FLAGSTAFF POINT Cape Royds, a bluff of kenyte lava about 80 feet high, showing results of marine erosion [Photo by David [To face p. 202 THAW 203 of 1908, the snow, 2 feet from the rock, was converted into a coarse-grained névé, graduating into ice as the rock was approached, and before the end of November a small rivulet was seen flowing from underneath the drift, whilst the surface, except near the edges, seemed to have remained comparatively unaffected. At Cape Royds, as observed at the Stranded Moraines later on, there was a periodicity in the thaw which was not governed by the amount of sun’s heat so much as by the complete, or almost complete, removal of the smaller snow-drifts, and the necessary lull until the snow-drifts had been renewed by a drift-laden blizzard or a snowstorm. Our observations of thaw at Cape Royds are naturally somewhat incomplete, as after December 1, 1908, there was no geologist left at the winter quarters. It is quite a common thing for snow-drifts to melt quite quickly on slopes exposed to the summer sun, and for the thaw-water to become frozen when it reaches a hollow where the sun has no direct effect. A well-marked example of this, much exaggerated by circumstances, was seen when the snow-drift on the ridge at the back of the Hut commenced to melt in December 1908. The thaw-water which ran below the house, where the sunshine could not penetrate, and the air temperature never rose above 32° F., froze at once, and never again thawed. Each day’s thaw added another layer, until the snow- drift had disappeared entirely from the hill, and there was a pool of ice 18 inches to 2 feet deep below the Hut. We are indebted to our biological colleague, Mr. James Murray, for the following information in regard to the summer thaw of the lakes at Cape Royds :— SUMMER THAW OF THE LAKES, CAPE ROYDS Accounts have already been given, in Chapter V., of the thaw observed by the Western Party in the Ferrar Glacier Valley, and the thaw-water streams are illustrated in Plate XVIII. Fig. 1 and Plate XIX. Fig. 2. 1908. Oct. 13. No open water in any lake. Nov. 4. Clear Lake. A few inches of water lying on the ice in narrow zone along the black rocky ridge. Noy. 14. No open water at any lake. Nov. 28. Blue Lake, pool at the Narrows (never thawed further), Pony Lake, several small pools. Noy. 29. Green Lake, thawing at edge. Noy. 30. Blue Lake. Pools on the ice at margin formed by thaw-water running down from drifts. Coast Lake, melted at edge. Dec. 11. Clear Lake. No melting except narrow band round the island which you could step across. (This lake never thawed more.) Dec. 13. Pony Lake, three ponds formed, the largest at hut; overflow by two streams, one going to the Rookery and the other to Arrival Bay. Dec. 29. Green Lake and Coast Lake, about half melted. 204 GENERAL GEOLOGY Jan. 2. Coast Lake all melted but a small patch. (In Blue and Clear Lakes found pools frozen.) Jan. 18. Coast Lake and Green Lake all melted. Feb. 2. Green Lake all frozen except hole 2 yards across in centre. Feb. 24. All lakes frozen, ice thick (1 foot or more in Coast Lake). Dec. 1 to 4. Maximum thaw on land. Snow gone from all Cape Royds District except little drifts at north side of peaks and ridges. Thaw-water from drift behind hut, flooded beneath hut (2nd December). Small streams running in all valleys, and their channels green all over with alge. Drygalski-Nansen Region. Little evidence of much work being accomplished by thaw-water was observed by us in this area. On December 22, 1908, we found a pool of thaw-water on the surface of the ice, fed by a subglacial stream coming from an old rock moraine on the piedmont about 2 miles off the coast. On December 22, 23, and 24 a thaw-water stream could be heard roaring along under the snow and glacier ice of Backstairs Passage, next to the northern granite cliff of Mount Crummer. This was evidently flowing at the bottom of the snow-filled fosse at the base of the cliff. This thaw-water formed a shallow lake about half a mile by a quarter of a mile over the surface of the old sea ice at the foot of the glacier. At this time avalanches were descending from time to time from Mount Crummer. At the south side of the Drygalski Ice Barrier Tongue, at the point where our route reached its farthest point east, we observed a glacial torrent channel entering a kind of estuary, or inlet, in the Barrier. The inlet was about half a mile in length, and then passed into a narrow torrent channel 10 to 20 yards wide and about 20 to 30 feet deep. The channel was cut chiefly out of drift snow, partly out of ice. The following is a sketch plan of this thaw-water channel (Fig. 59). A curious and very beautiful etching effect was observed on the Larsen Glacier portion of the Drygalski-Reeves Piedmont on J anuary 31 and February 1,1909. The surface of the piedmont was found to be covered with curved anastomosing plates of thin ice, dipping at angles of approximately 30° or so, and on the whole, while the direction of dip varied, showing a general tendency to dip away from the north towards the south. Sledging over these inclined thin sheets of ice might be compared to tramping over a wilderness of cucumber frames inclined at the above angle, the ice plates sometimes supporting one’s weight, sometimes giving way with a crash, and letting one through up to one’s thighs on to the surface of the solid ice below. Our colleague Murray’s explanation of a somewhat similar structure probably applies to this region also : *— “Tn the height of summer the combined action of the sun and air on compacted * Heart of the Antarctic, vol. ii. p. 341. THAW EFFECTS 205 =—== = 2 SS SS a ~ 1S ES SSS ; : ) 7 Glacier ice SNE forming large SS =, re Le ONEeG domes Z eye about 100 feet = above Sea level Miss “1 — Yo a Sea ice = Lg etees ey, VZZ2 : i; Small Inlet = ee // SEZ ie Zz im. I/d snow (2) dune \ \ >, about 2OFt high Scale. Fie. 59. Sketch plan showing small inlet receiving the drainage of a surface glacial stream on the southern side of the Drygalski Ice Barrier Tongue at a point 20 miles west of its seaward end snow-drifts caused deep erosion of the snow. A kind of stratification resulted, which appeared to have no relation to any original stratification of the snow. Thin flat layers of ice were formed, separated by cavities. These dipped at a gentle angle 2D 206 GENERAL GEOLOGY to the south, that is to say, their edges were directed towards the sun at the time of day when it is highest. These ice plates were so fragile that they collapsed in multitudes as we walked over the drifts, and a slight breeze whirled quantities of them along, often rolling them on their edges.” In the Drygalski-Reeves Piedmont area these plates were much thicker, frequently quite strong enough to support the weight of a man. There can be little doubt that this remarkable and beautiful structure is the result of etching of old snow-drifts by the heat rays of the sun. The thawing of the surface snow sets free thaw-water, which under gravity creeps down the planes of bedding of the snow, being arrested by the less pervious layers, and there during the cold of night it freezes, and the process being repeated from day to day, the remarkable inclined plates of ice result.* This is not a complete explanation of the phenomenon, for, as Murray remarks, ‘“‘a stratification resulted which appeared to have no relation to any original stratification of the snow.” Transportation. The glacier itself is still a very important agent of transport- ation, but the amount of this work it does to-day is nothing to what it must have done at or near its maximum period of glaciation. All along the length, wherever the slope of the sides of the valley is gradual enough to support debris, they are strewn with a miscellaneous collection of rock which, for many hundreds of feet above the present level of the ice, can only have been carried and deposited there by the glacier. In many places the rock is mingled with angular fragments, obviously derived by frost-weathering from the neighbouring cliffs, but the presence of the old lateral moraine is still indicated by the number of subangular and rounded blocks of rock in the lower portion of the screes. Another important agent in removing the light material is the wind, and its power is shown by the amount of small sediment which is scattered over and in the surface ice of the glacier. Lastly, the agents which are having most effect at the present day are the many streams of thaw-water which seam the glacier in every direction during the thaw- season. Immense quantities of fine sediment must be annually removed in this manner in spite of the shortness of the thaw-season, for all these streams that we saw had a good deal of small gravel in them, and those pouring into the lake near the Solitary Rocks were thick with sediment. The result of this transportation is well seen in the New Harbour Dry Valley, from which the ice has retreated, leaving a vast hummocky sheet of the ice- and water-transported debris exposed to view. * Unfortunately we had exhausted the last of our photographic plates before we descended from the Magnetic Pole Plateau on to this unique type of glacial surface, and so are unable to figure it. MARINE EROSION 207 MARINE EROSION There is evidence of a considerable amount of marine erosion having taken place in the Ross Sea and McMurdo Sound areas since the close of the phase of maximum glaciation. At Cape Barne, for example, there is a sheer cliff about 200 feet in height which has obviously been cut out by the sapping action of stormy seas in summer time. During the colder periods of the year obviously no marine erosion can take place on account of the surface of the sea being crusted over with ice. Flagstaff Point, near our winter quarters, exhibits a sheer cliff of marine erosion about 80 feet in height. (Plate LIX. Fig. 3.*) The denuding force of the sea also expends itself of course on piedmont ice, ice barriers, and glacier ice tongues. In the case of the Nordenskjéld and Drygalski Ice Tongues the combined effect of sea and wind erosion had been to round off and level off the weather side of the ice tongue. The same feature was noticeable at Glacier Tongue. Throughout its whole length the Ross Barrier exhibited a deep wave-worn groove at its base. All icebergs, excepting those quite freshly calved, showed the same feature. The terraces, which were conspicuous near Cape Bird and above Backdoor Bay near Cape Royds, may be due to marine erosion, or possibly may mark former levels of fresh water lakes at the margin of the great lobe of the Ice Barrier when it completely filled McMurdo Sound. In this case these terraces are comparable with the parallel roads of Glen Roy or the seter of Scandinavia and Greenland. Even when high waves are raised in the open sea by the action of blizzards, like the great blizzard of February 16, 17, and 18 in 1908, their effect on the coast is not entirely destructive, but in the long run is protective, for towards the end of that blizzard we observed that the coast-line for some distance inland was coated with a thick crust of ice formed from the freezing of the spindrift and spray. This effectually protected the rocks fringing the coast from further marine erosion. The protective character of sea spray in strengthening and consolidating the snow- drifts of the ice-foot has already been explained in Chapter VIII. At the same time, it is obvious that the wetting of extensive cliff faces with sea spray by the blizzard winds, followed by a quick freezing of the films of sea water, which have penetrated the joints and cleavage planes of the rocks, must have a very strong destructive influence, owing to each film of ice thus formed wedging off flakes of rock, In this way marine erosion considerably aids normal frost weathering in the work of rock destruction. * See also Plate II. Fig. 2 illustrating the great wave-worn cliff at Cape Washington, CHAPTER XI VULCANISM Tue chief voleanic trend lines have already been described in Chapter I., dealing with the physiography of the region. In this chapter it has been explained that the chief volcanic centres are situated at the ends of a network of faults running partly parallel to the great horst, partly more or less rectangular to it, as shown on the accompany- ing Plate LX. The volcanoes may probably be grouped in two main zones. Firstly, the zone to the east of the horst; secondly, that which lies to the west. The latter has not yet been definitely proved to be volcanic, but the shape of many of the hills on the western side of this horst, such as Mount Judd, Mount Bowen, Mount Priestley, Mount Mackintosh, suggest that they are probably volcanic, and the rocks of which they are composed appear to be very black. The existence of this western zone may be looked upon at present as problematical, and our attention may now be directed to describing the voleanoes on this belt to the east of the great horst. This zone, having a general north and south trend, is crossed by strong tectonic lines running either due east and west, or from about E.S.E. to W.N.W. One of the strongest of these cross lines is that upon which Mounts Terror, Terra Nova, and Erebus are situated. This great fracture zone runs through Cape Royds, and, according to the discovery just reported by Mr. F. Debenham, undoubted traces of it are met with at New Harbour in the form of very recent craters of basic lava.* These occur near New Harbour. Thus this strong transverse line has a length of nearly 100 miles in an east and west direc- tion measured from Cape Crozier to Dry Valley. Our description will commence with Erebus and its parasitic cones, touching next on Cape Royds, the Dellbridge Islands, Hut Point, and finally Mount Bird, all these localities being situated on Ross Island, which is itself entirely composed of lavas and tufts of Cainozoic age, except for some insignificant inclosures of what appears to be Beacon Sandstone in the lavas. Mount Erebus. The general appearance of Mount Erebus is well shown in the photograph by Dr. D. Mawson forming the frontispiece to this Memoir, as well as in Plate II. It will be noticed that, if one looks across the ice in the foreground at Backdoor Bay, one sees a wide belt of mounds of moraine gravel, amongst which occur at intervals patches of raised marine muds, together with shallow ice-filled * Press account of scientific results of the Scott Expedition. 208 PLATE LX tong East. ]I6* Long west GENERAL MAP * showing the chief tectonic lines geological faults foliation,and Volcanic craters of SOUTH VICTORIA LAND ano THE ROSS BARRIER REGION OF THE ANTARCTIC. — ‘0 Statute Milles. Geographical Miles. Natural Scale | - 6.000000. D ‘ HGALSK! Orga Se \ Tre FRANKUN t \ REFERENCE. eeccceee Probable Fautts Qeeeee= Possible Faults. a Foliation. © °o Volcanic Foci. Probable volcame Foci SOUTH POLE + 210 GENERAL GEOLOGY lakes or dried-up lakes, the floors of which are strewn with remains of algz and diatoms. These moraines ascend to a height of from 1000 to 1100 feet above sea- level. In the description of the raised marine deposits attention is called to the fact that the one near Cape Barne, at an altitude of about 160 feet above the sea, is actually resting on a foundation of ice. It is very probably the case that there is still a considerable amount of ice, perhaps a relic of the ice of the former Great Ice Barrier, still preserved under this moraine debris. A little to the right of the centre of the photograph above the termination of the moraines two parasitic cones are visible. Of these, the one described in detail, Mount Cis, is the one which lies to the right of the other. In the centre of the picture, and in the middle distance at the foot of the steep cone proper, is a large and very conspicuous black parasitic cone surrounded by a very deep snow fosse. This is probably on the line of fracture trending from the centre of the second crater towards Cape Royds. On the extreme left of the great cone there is just visible the rugged outline of the great cliff forming part of the first and oldest crater of Erebus. This oldest crater is now largely in ruins, with only small portions of the crater wall preserved at intervals. Its diameter is about 8 miles, as estimated by Mr. H. T. Ferrar,* which agrees closely with our own measurements. Unfortunately on our ascent of Mount Erebus in March 1908 we were unable to visit this first and oldest crater. Its general appearance, as viewed from the summit of the active crater, is shown on the accompanying Plate LXI. Fig. 2. The greatest altitude attained by the rim of this oldest crater was not accurately measured, but appears to be of the order of about 8000 feet.f On its inner edge is a stupendous cliff, almost vertical, apparently over 2000 feet in height. Thus the oldest crater was a gigantic explosion crater somewhat analogous to that of ‘Teneriffe. Within this rises the second crater, with its steep outward slope showing that concavo- convex outline so characteristic of cones formed of volcanic ejectamenta. It is buttressed by gigantic arétes of black kenyte lava. At the foot of the steep slope of this second crater we observed some smoothed surfaces of ice, evidently representing frozen lakes. These have probably been formed by the thaw-water resulting from the melting of ice and snow in contact with the black kenyte lavas, which in summer absorb so much of the sun’s heat that they become quite warm to the touch. This second crater terminates in a magnificent perpendicular—in places overhanging— wall of black kenyte lava. The second crater itself is fully 3 miles in diameter from north to south, and about 2$ miles from east to west. The great cliff forming its inner boundary wall is in places at least 80 feet in height. The crater itself is piled up higher towards its southern end by the material of the third and fourth craters, the * National Antarctic Expedition, 1901-4, Geology. + According to the estimate of a party which examined this old crater in 1912 on their way to the summit of the mountain, it reaches a height of about 10,000 feet (R. E. P.). 211 YAIA 1940504 “OGL ‘TT Gorey 04 © youeyy ‘snqoay yunoy Jo Jueose qsay oyy epeur yorya Aqaed jo aqnoa Surmoys urypg ae LPG PD Ey Z ISN) ito ne S Vii Seg “) N ss) rs =} 2 [ea] o 2 : GN worl A dso ie fH Re ne EE aa ee 72 ie De Sosa es ~ =) I dwe, jo) 19006g Lom aa pee jk Woo SS peer ee ee Ls Renter eeyes owes & mm, 444d 187 P10 ” et 1m, we rr pre eT Bucy eH sesey cf SUOLPRIIBA otjouseur [B00, pueB S.1e4eI0 JO worytsod \ ; ; &\\ \ SUN So De pe mouse’ 0, org 7 NR ray Tis.