HAROLD B. LEE LIBRARY BRIGHAM YOL-\G LNIVERSn PROVO, UTAH Digitized by the Internet Archive in 2009 with funding from Brigham Young University http://www.archive.org/details/lakebonnevilleOOgilb m UNITED STATES GEOLOGICAL SURVEY J. W. POWELL, DIRECTOR LAKE BONNEVILLE BT GROVE K^RL GILBERT ^^Ak WASHINGTON GOVERNMENT PRINTING OFFICE 1S90 fTAPnTTiT} 1 TV r mr> \rjy BR riA rtx.U'. U. UlAM CONTENTS. I'age. Letter of Transmittal xv Preface xvij Absthact of Volume xix Cjiaptek I. — Inti:oductiox 1 Interior Bajiiis o The Great Basiu 5 History of Investigatiou j) •The Bonneville Basin 20 Clirouologic Nomenclature :;2 Chapteu II.— The Topographic Features ok Lake Shores 23 Wave Work o'J Littoral Erosion oij TbeSeaCliflf 34 The Wave-cut Terrace 3;, Littoral Transportation 37 The Beach 39 The Barrier 40 The Subaqueous Ridge 43 Littoral Deposition 46 Embankments 46 The Spit 47 The Bar 43 The Hook 50 The Loop 55 The Wave-built Terrace 5.j The V-Tcrrace and V-Bar i,7 Drifting Sand ; Dunes 5'j The Distribution of W'ave- wrought Shore Features 60 Stream Work ; the Delta 60 Ice Work ; the Rampart 71 Submergence and Emergence 72 The Discrimination of Shore Features 74 Clifis 75 The Cliff of Differential Degradation 70 The Stream Cliff ■..., 75 The Coulee Edge 76 The Fault Scarp 76 The Land-slip Cliff 77 Comparison 77 . Terraces 78 The Terrace by Differential Degradation 78 The Stream Terrace 79 The Moraine Terrace 61 VI CONTENTS. Page. Chapter II— The Topographic Features of Lake Shores— Continued. The Fault Terrace 83 The Land-slip Terrace 83 Comparison 84 Ridges 86 The Moraine 86 The Osar or Kama ; 87 Comparison 87 The Recognition of Ancient Shores 88 Chapter III.— Shores of Lake Bonneville 90 The Bonneville Shore-line 93 The Question of a Higher Shore-line 94 More Ancient Lakes 98 Outline of the Lake 101 Extent of the Lake 105 Shore Details lOG Embanlauent Series Ill Determination of St ill- water Level 122 Depth .". * 125 The Map 125 _ The Provo Shore-line 120 Outline and Extent 127 Shore Characters 12S > Deltas 129 The Underscore 130 Embankment Series 131 The Map 134 The Stansbnry Shore-line 134 The Intermediate Shore-lines 135 Description of Embankments 135 Grantsville 135 Preuss Valley 130 The Snow-plow 137 Stockton and Wellsvillo 137 DoveCretk 137 Comparison of Embankments 137 Hypothesis of Difl'ereutial Displacement 140 Hypothesis of Oscillating Water Surface 141 Superposition of Embankments 147 The Snow-plow 147 Reservoir Butte 148 Stockton 149 Blacksmith's Fork 151 Dove Creek 151 Double Scries in Preuss Valley 152 Deltas 153 American Fork Delta 155 Logan Delta 159 Summary 16G Tufa 167 R^sum^ 169 Chapter IV.— The Outlet _ 171 Red Rock Pa.s8 173 Marsh Valley 170 The River 170 \ CONTENTS. VII Page. CHArTKR IV.— The Outlet— Continued. , The Gate of Bear River 178 The Question of an Earlier Discharge 180 The Old River Bed 181 Other Ancient Rivers 184 Outlets and Shore-lines 186 Chapter v.— The Bonxkvii.le Beds 183 Lower River Bed Section 189 Leininptoi) Serf ion 19!j Upper River Bed Section 194 Yellow Clay 194 First Gravel 194 White Marl 195 Lower Sand 195 Second Gravel 195 Upper Sand 19G Upper Gravel IDG Oscillations of Water Level .. 19(; Height of the First Maxim nm i;i9 The Whiteness of the White Marl 200 Source of Material 20:1 Composition of Lake Water 204 Experiments 305 Deposition by Desiccation 208 Organic Remains 209 Joint Structure 211 Chapter VL— The History ok the Box.veville Basix 214 The Pre-Bonneville History 214 Alluvial Cones and Aridity 220 The. Post-Bonne ville History >2.t2 Subdivision of the Basin 222 Snake Valley Salt Marsh . 223 Sevier Lake 224 Salt Bed 225 Rush Lake 228 Great Salt Lake 230 Surveys 230 Depth 230 Gauging 230 Oscillations since 1875 .2:13 Oscillations prior to 1875 239 Changes in area 243 Causes of Change 244 Future Changes 250 Saline Contents 251 Sources of Saline Matter 254 Rate and Period of Salt Accumulation 255 Fauna 258 The General History of the Bonneville Oscillations 259 The Topographic Interpretation of Lake Oscillations 262 Hydrographic Hypothesis 263 Orogenic Hypothesis 263 Epeirogenic Hypothesis 264 The Climatic Interpretati. S. Wociilward 4'il Apfexdix C— On the Elevation of the Sukface of the Uonneville Basin by Ex- pansion DVE TO CHANGE OF CLIMATE. By R. S. Wl)()iK\ llltl 425 InijEX 427 TABLES. Table I. DiinoDsions of Lakr.s 106 II. Ei!ib;ii)kiiieiit Series of tlio Bcjiiiicvillf Sliciif -liuo 119 III. Analyses of BoonCTille Sediiiiciits 201 IV. CoiKlcnsed Results of Analyses in Tal)le III 202 V. Mineial Couteuts of Frosb Waters in the Salt Lake Hasin 207 VI. Analysis of Sevier Lake Desiccation-products and Brine 227 VII. Datutu Points Connected with (lie Gauging of Great Salt Lake 23:! VII r. Record of the Oscillations of Great. Salt Lake 2:53 IX. Analyses (vf Water of Great Salt Lake 2o3 X. Accuniulatiou Periods for Substances Contained in tlie Brine of Great Salt Lake 255 XI. Fre.sh-water Shells in tbe BonueviUe-Laboutan Area 298 XII. Measurements of F!iniiiiii crossing Alluvial Cone, near Salt Lake City 348 XLV. Maj) showing Lines of recent Faulting - 352 XLVI. Deformation of the Bonneville Shore-line 3G6 XLVII. Deformation of the Provo Shore-line 372 \LVI1I. Vertical Interval between the Bonneville and Provo Shore-lines 372 XLIX. Map showing the Glaciated Districts of the Bonneville Ba.->in 374 L. 1 heorctic Curves of Post-Bonneville Deformation 374 LI. Map of Black Rock and vicinity, Utah, showing the position of the Black Rock Bench ^ 300 Fig. 1. Sheep Rock, a Sea Cliff 35 2. Section of a Sea Cliff and Cut-Terrace in Incoherent Material 30 3. Section of a Sea Cliff and Cut-Terrace in Hard Material 3(") 4. Section of a Beach 39 5. Section of a Cut-and-Built Terrace 40 6. Section of a Barrier 40 7. Section of a Linear Embankment 49 8. Map of JJraddock's Bay and vicinity. New York, showing Headlands connected by Bars. 50 9. Map of the head of Lake Superior, showing Bay Bars 51 10. Diagram of Lake Ontario, to show the Fetch of Waves reaching Toronto from different directions 53 11. Map of the Harbor and Peniusnla (Hook) at Toronto 54 12. Section of a Linear Embankment retreating Landward 5G l;!. Section of a Wave built Terrace 56 14. Section of a Delta 68 15. Vertical Section in a Delta, showing the typical Succession of Strata 70 IC. Section of a Rampart 71 17. Ideal Section, illustrating the formation of a Moraine Terrace at the side of a Glacier. 82 18. Ideal Section, showing the internal structure of grouped Lateral Moraine Terraces 82 19. Ideal Section of Alluvial Filling against Front Edge of Glacier 82 20. Section of resulting Frontal Moraine Terrace 83 21. Bonneville and Intermediate Embankments near Wellsville, Utah, showing coi;tra8t between Littoral and Subaerial Topography 98 22. Butte near Kelton, Utah 108 23. Bars near George's Ranch, Utah 114 24. Limestone Butte near Redding Spring ; an Island at the Provo Stage 129 25. Compound Hook of an Intermediate Shore-line near Willow Spring, Great Salt Lake Desert 145 26. Generalized Section of Deltas at the Month of American Fork Canyon 156 27. Partial Section of Deltas at Logan, Utah 162 28. Section showing succession of Lacustrine and Alluvial Deposits at Lemington, Utah. 192 29. The Upper River Bed Section 194 30. Diagram of Lake Oscillations, inferred from Deposits and Erosions 198 3L Sevier Lake in 1872 227 32. Annual Rise and Fall of the Water Surface of Great Salt Lake 239 33. Non-periodic Rise and Fall of Great Salt Lake » 243 34. Rise and Fall of Water in the Bonneville Basin 262 35. First Diagram of Glaciation Theory 289 ILLUSTRATIONS. XIII Page. Fig. 36. Second Diagram of Glaciation Theory 293 37. Diagram to illustrate tUe Alternation of Volcanic Eruption and Littoral Erosion on Pavaut Butte 327 38. Section of Pavant Butte 327 39. Sectional Base of Pavaut Butte, showing remnant of earlier Tuft' Cone 328 40. Theoretic Section of Fumaroli- Butte 333 41. Dnnderberg Butte 335 42. Profiles of ihe Rock Canyon Delta 344 43. South Half of Kocli Canyon Delta.showing Fault Scarps MS 44. Profile of the South Moraine at tlio Mouth of Little Cottonwood Canyon, showing the effect of Faulting 347 45. Profile of Fault Scarps near Big Cottonwood Canyon 347 46. Shore-lines and Fault Scarp near Farniiugtcvn, Utah 350 47. Profile of Fault .Scarps near Ogden Canyon, Utah 350 4S. Diagram to illustrate theory of Grouped Fault Scarps in Alluvium 355 49. Generalized cross-profile of mountains and valleys, illustrating Post-Bonneville Dias- trophic Changes 367 50. Diagram of Post-Bonneville Diastrophic Changes 367 51. Cross-section of Ideal Lenticular Lake Basins 423 ERRATUM TO PLATE. Plate XLII. For "Big Cottonwood Cr." read Dry Cottonwood Cr - 346 LETTER OF TRANSMITTAL. United States Geological Survey, Division of the Great Basin, Washington, D. C, June 29, 1889. Sir : I have the honor to transmit heremth the manuscript of a final report on Lake Bonne^-ille. To yourself, and to the Hon. Clarence King, under whose direction a. large part of the investigation was conducted, I am indebted not only for the facilities which have rendered the research possible, but also for never- failing kindness and encouragement, that have added zest and pleasure to the work. Veiy respectfully, your obedient serA-ant, G. K. Gilbert, Geologist in Charge. Hon. J. W. Powell, Director U. S. Geological Survey, Washi/igton, D. C. XV XYIII PREFACE. in the Second Annual Report of tlie Survey. A partial discussion of the deformation of the plane of the Bonneville shore-line was presented to the American Society of Naturalists at its Boston meeting, 1885. The Fifth Annual Report contained a paper on the topographic featru-es of lake shores. The subjects of the first and second of these publications are here greatly amplified. The text of the third is in large part re])eated in the .second chapter of tliis volume; liut the specialist will find new matter on pages 25-26, 30-31, 39, 42-45, 53-55, 63-65, 71, 80-83. He Avill also note that the discussion of rhythmic embankments takes a new foi-m in another chapter. Tft those assistants, colleagues, and fellow students who have contrib- uted to my store of material I have endeavored to give credit in the pages of the text, but it has been impos.sible there to acknowledge my multifarious obligations for friendly aid, advice, and criticism. To numerous citizens of Utah and Nevada I am indebted for substantial favors, and some parts of the woi-k woidd have been very difficult without the special facilities afiorded by the rai]v,ays of Utah. a K. G. ABSTRACT OF VOLUME Chapter I: IXTROorCTlox.— Diastrophic iimcesBes tend to the formation of closed basins; atmos- pheric, to tlieir (Icstinctioii. lu arid regions formative processes prevail; iu humid, destruc- tive.— The Great B;isin is the chief North American district of interior drainage, but is inferior to those of otlier continents. Its dry climate is caused by certain rehitious of winds and ocian torrents. — The Pleistocene lakes of Ihe Great liasin have been previously studied by .Stansbury, lieckwith, Blake, Simpson, Engelnianu, Whitney, King, Hague, Emmons, Hayden, Bradley, Poole, Howell, and I'lalc. — The Bonni'ville Basin is the northeastern jiart of the Great Basin, .and includes one-fourth its area. — Tlie term Pleistocene is preferred to Quaternary, as being less cnnuotive. Chaptek II: Topographic Featiuks ov Laice Suores.— The waves and .shore currents of lakes are produced by the same winds. They work together iu littoral transportation. Where a shore current 18 accelerated, littor.il erosion occurs ; where it is retarded, littoral deposition. W^here the current departs from the shore a spit is built. — The delta formation has three parts. The upper and middle parts are coarser than the lower; the bedding of the middle is more highly inclined than that of the n]iper and lower. — An adolescent coast is marked by narrow terraces and absence of shore drift and embankments; numerous enibankuients mark the mature coast. — Wave work renders coast linns less tortuous. — Clitfs, terraces, and ridges, due to shore processes, may be distinguished from similiar features produced otherwise by the study of their forms, structures, and relations. Chapter III: Shores of Lake Bonneville.— The Bonneville shore-lino is about 1,000 feet above Great Salt Lake, and compasses au area of 19,7."i0 sijuare miles. The Provo shore-line contours the basin 375 feet lower, and is the strongest marked of all the shore-lines. Between the Bonne- ville and the Provo ani the Intermediate shore-lines. — The synchronism of the entire Bonneville shore-line is shown by its series of embankments. — The Internudiate embankments are ryhthmic products of the irregular oscillations of the water surface. — Deltas belong chiefly to the Provo shore-line. — Tufas were deposited just below the water surface. — The chronologic order of the shore-lines is (1) Intermediate, (-') Bonneville, ('^) Provo. Chapter IV: Outlet. — At the level of the Bonneville shore-line the lake overflowed, sending a stream from the north end of Cache Valley northward to thr Snake River. The sill of the outlet was of alluvium, but with a limestone ledge beneath. Th(i alluvium was easily washed away, and a prism of water about 375 feet deep went out by a debacle, lowering the lake to the level of the limestone ledge. This level coincides with the Provo shore-line. Chapter V: Boxxkville Beds. — Within the circle of the Bonneville shore-line are lake sediments of the same date. The White Marl, relatively thin and calcareous, lies above the Yellow Clay, rela- tively thick and aluminous. — Tbey are separated by a jdane of erosion, testifying to a dry ejioch between two humid epochs. The calcareous character of the njiper member is theoretically con- nected with the burial of salts during the dry ejioch. — The strata contain fresh-water shells of living species.— They are divided by a system of parallel joints, ascribed to earthijuake shocks. XX ABSTKACT OF VOLUME. Chapter VI: History op Bonnkville Basin-. — Previous to the Boiinfville history the basin was arid. The first rise of the lake was without overflow, and was long niaiiitaineil ; the Yellow Clay was then deposited. The second rise went 90 feet higher, causing overflow, bnt was of shorter duration ; the White Marl was then dejiosited. The final drying divided the basin into a dozen independent basins, the largest of which contains Great Salt Lake. Since 1845 that lake has repeatedly risen and fallen through a range of 10 feet. — The history of Lake Bonneville is par- alleled by that of Lake Lahoutan, and each is connected with a history of glaciation in adjacent mountains. This connection, the depauperation of the fossil shells, and an analysisof the climatic conditions of glaciation, lead to the conclusion that the lacustrine epochs were ejiochs of relative cold. Chaptkr VII: Lakk Boxnevillkand Volcanic Eruption. —The group of small craters and basaltic lava fields mar Fillmore, Utah, are closely related to the lake history. Some eruptions took place beneath the water of the lake, others since its disappearance, and others again during the inter- lacustrine epoch. — Numerous basaltic eruptions occurred in the lake area before the lake period, and at still earlier dates rhyolite was extravasnted. Chapter VIll : L.vkk Bo.nnf.ville axd Diastrophism.— Orogenic change during a period subsequent to the lake is shown by fault scarps, The formation of fault scarps is accompanied by earth- quakes.— Epcirogeuic change during a period subseijucut to the lake is shown by the deformation of the planes of the shore-lines. Under the postulate that the doming of the planes is due to the drying away of the lake, it is concluded that the strains induced by the unloading of the areas exceeded the elastic limit of the material and caused viscous distortiou of the earth's crust. This result, taken in connection with the phenomena of mountain uplift, leads to an estimate of the strength of the crust. Chapter IX : Age of the Equus Fauna. — The Eqnus fauna at its type locality is contained in lake beds correlated by physical relations with tin- n|ipermost of the Lahontan and Bonneville beds. The fauna, previously called later Pliocene, is thus shown to have lived in late Pleistocene time. LAKE BONNEVILLE. BY G. K. GIIiBERT. CHAPTER I. INTRODUCTION. This volume is a contribution to the later physical history of the Great Basin. As a geographic province the Great Basin is characterized by a dry climate, by interior di'ainage, and by a peculiar mountain system. Its later history includes changes of climate, changes of drainage, volcanic eruption, and crustal displacement. Lake Bonne\'ille, the special theme of the vol- ume, was a jDhenomenon of climate and di-ainage, but its complete history includes an account of contemporaneous eruption and displacement. When the work of the geologist is finished and his final comprehensive report written, the longest and most • important chapter will be upon the latest and shortest of the geologic periods. The chapter will be longest because the exceptional fullness of the record of the latest period will enable him to set forth most completely its complex history. The changes of each period — its erosion, its sedimentation, and its metamorphism — obliterate part of the records of its predecessor and of all earlier periods, so that the order of our knowledge of them must continue to be, as it now is, the inverse order of their antiquity. The great importance of the chapter on the latest period lies in the fact that it will contain the key for the decipherment of the records of the earlier. The records of those periods consist of the products of various MON I 1 1 2 LAKE BONNEVILLE. processes of change, and these products ai-e to lie interjireted only thi-ough a knowledge of the processes themselves. Many of the processes can be directly observed at the present time, and it is by such obsei-vation, com- bined with the study of freshly fornied and perfectly preserved products, that the relation of product to process i.s. learned. It is through the study of the i)henomena of the latest period that the connection between jiresent l)roce.sses of change and the products of past changes is established. In view of these considerations the Bonneville study has been con- ducted with a double object, the discovery of tlie local Pleistocene history and the discovery of the processes by which the changes constituting this history were wrought. INTERIOR BASINS. In physical geography the terms "basin" and "di-ainage district" are synonymous, and are used to indicate any area which is a unit as to drain- age. The basin of a stream is the tract of country it drains, whether the stream is a great river or the most insignificant tributary to a river. We thus speak of the basin of the Ohio and of the basin of the Mississippi, and say that the latter includes the fonner. And it may be said in general that the basin of any branching stream includes the basins of all its tributaries. The basin of a lake is the tract of country of which it receives the drainage, and it includes not only the basins of all aflBuent streams but the area of the lake itself. The tenn "lake basin" is also applied to the depres- sion occupied by the water of a lake and limited by its shores, and wherp confusion might arise from the double use, the ■wider sens-T is usually indi- cated V)y the adjective "hydrogra])hic" or its equivalent. If the lake has an outlet its basin is a part of the basin of the effluent stream, but if it has no outlet its basin is complete in itself, and is wholly encircled by a line of water-parting. In such case it is called a continental, or interior, or closed, or shut, or drainless basin. If an interior basin exists in a climate so arid that the superficial flow of water, AA'hich constitutes drainage, is only potential and not actual, or else is occasional only and not continuous, it contains no perennial lake and is called a diy basin. INTERIOR BASINS. 3 The boundaries separating' basins are water-partings or divides, and these are of all characters, from the acute crests of mountain ranges to low rolls of the plain scarcely discernible by the eye. Interior basins are com- pletely euciix'led by lines of water-pai-ting. The existence of interior basins depends on two conditions: a suitable topographic configuration and a suitable climate. The ordinary process of laud sculpture by mnning water does not produce cup-like basins, but tends on tlie contrary to abolish them. Wherever a topograj)hic cup exists the streams flowing toward it deposit within it their loads of detritus, and if they are antagonized by no other agent eventuallv fill it. If the cup con- tains a lake with outlet the outflowing stream erodes the rim of the basin, and eventually the lake is completely drained. The Avork of streams occassionally produces topographic cups by the rapid fonnation of alluAaal dejiosits where two streams meet. If the power of one stream to deposit is greatly increased, or if the poAAer of the other stream to erode is greatly diminished, the one may build a dam athwart the course of the other and thus produce a lake basin. The great agent in the production of lake basins, or the agent Avhicli ■ has produced most of the large basins, is diastrophism,^ and in a majority of the cases in which basins are partitioned off by the alluvial process just described, the change in the relative power of the streams is brought about by diastrophism. C)ther basin-forming agencies are volcanic eruption, limestone sinks, wind waves, dunes, laud slides and glaciers. By far the greatest number of topographic cups are due to glaciers; but with these we are not now concerned. The basins of ordinary lakes are distinguished from interior basins by ovei-flow, and that depends on climate. The rainfall of each basin is or may be disposed of by three processes: first, evaporation from the soil and 'I fiuil it advantageous to follow J. W. Powell in the use of diastrophiam as a general t«rm for the process or processes of deformation of the earth's crust. The products of diastrophism are conti- nents, plateaus and mountains, ocean beds and valleys, faults and folds. Diastrophism is coordinate with volcanism, and is tlie synonym of displacement and di.ilocation in the more general of the two geologic meanings acquired liy each of those words. Its adjective is di(i«trophic. It is convenient also to divide diastrophism info orogeny (mountain--. .aking) and epeirogeny (continent making). The words epeirogeny and epeirogenic are defined ir the opening paragraph of chapter VIII. 4 LAKE BONNEVILLE. from the vegetation supported by it; second, evaporation from a lake sur- face; third, outflow. If the rainfall is sufficiently small, it is all retm-ued to the air b}- evaporation from the soil and vegetation, and the basin is diy. If it is somewhat larger, the portion not directly evaporated accumulates in the lowest depression, forming a lake, from the surface of which evaporation is more rapid. The area of the lake surface is determined by the area of the basin, the rainfoll and the local rates of evaporation. The basin is closed so long as a lake sufficient for the purpose of evaporation does not require such an extent as to cause it to discharge at the lowest point of the rim. The area enclosed by a contour passing through the lowest point of the rim, the total area of the basin, and the local climate are tJie three factors which determine whether a given topographic cup shall constitute an interior basin. If the area of a topographic cup and the area of the maximum lake it can contain are nearly identical, it may constitute an in- terior basin in a reg'ion of humid climate. If the contour throucnli the lowest point of the rim encloses an area very small in comparison with the entire basin, the maintenance of an outlet is not inconsistent mth an arid climate. If there were no erosion and sedimentation, unchecked upheaval and subsidence would gi-eatly multiply the number of basins. On the contrary, ' if all displacement should cease, and the foundations of the earth become stable, erosion and sedimentation would merge all basins into one. The actual state of the earth's surface is therefore at once the result and the index of the continuous conflict between subterranean forces on the one hand and atmospheric on the other. The two processes which destroy ba- sins are conditioned by climate. In an arid basin the inwa.shing of detritus is slow and there is no outflow to corrade the rim; but vrith abundant rain- fall the accumulation of detritus is rapid and corrasion conspires -n-ith it to dimini.sh the inequality between center and rim. In arid regions, therefore, the formative subterranean forces are usually \-ictorious in their conflict with the destructive atmospheric forces, and as a result closed basins abound; in humid regions the destnictive agencies prevail and lake basins are rare. In the present geologic age it is necessary to restrict this generalization to lands in the lower latitudes, because the glaciation of the last geologic period created an immense number of lake basins in humid regions of high latitude, and ninning water has as yet made little progress in their destruction. TOPOGRAPHY OF THE GREAT BASIN. 5 7 THE GREAT BASIN. The major part of the North Amencau continent is drained by streams flowing to the ocean, but there are a few restricted areas ha^'ing no out- .ward di-ainage. The largest of these was called by Fremont, who first achieved an adequate conception of its character and extent, the "Great Basin," and is still universally known by that name. It is not, as the title might suggest, a single cup-shaped depression gathering its waters at a com- mon center, but a broad area of varied surface, naturally divided into a large number of independent di-ainage districts. It lies near the western margin of the continent and is embraced bv rivers tributarv to the Pacific Ocean. On the north it is bounded by the drainage basin of the Columbia, on the east by that of the Colorado of the "West, and ou the west by the basins of the San Joaquin, the Sacramento, and numerous minor streams. The central portion of the western water-parting is the crest of the Sierra Nevada, one of the greatest mountain masses of the United States, and far- ther south high mountains constitute much of the boundary. The northern half, of the eastern boundary is likewise high, winding through the region of the High Plateaus. The remainder of the boundary does not follow any continuous line of upland, but crosses mountain ranges and the intervening valleys without being itself marked by any conspicuous elevations. It is defined only through a stud}" of the drainage. The general form of the area, as exhibited on Plate II, is rudelv triauOTilar, with the most acute ansfle southward. The extreme length in a direction someAvhat west of north and east of south is about 880 miles, the extreme breadth from east to west, in' latitude 40° 30', is 572 miles, and the total area is approximately 210,000 square miles. Of political di\-isions it includes nearly the whole of Nevada, the western half of Utah, a strip along the eastern border of California and a large area in the southern part of tlie State, another large area in south- eastern Oregon, and smaller portions of southeastern Idaho and southwest- em Wyoming. The southern apex extends into the territory of Mexico at the head of the peninsula of Lower California. The region is occuj^ed by a number of mountain ridges which betray system by their parallelism and by their agreement in a peculiar structure. 6 LAKE BOXNEVILLE. Tlieir general trend is northerly, inclining eastward in the northern part of the basin and westward at the south. The individual ridges are usually not of great length, and they are so disposed en echelon that the traveler winding among them may traverse the basin from east to west without crossing a mountain pass. The type of structure is that of the faulted mono- cline, in which the mountain ridge is produced by the uptilting of an oro- genic block from one side of a line of fracture, and it has been named (from the region) the Basin Range tj'^jie. Its distribution, however, does not coin- cide perfectly with the district of interior drainage. On the one hand the Great Basin includes along its eastern margin a portion of the Plateau province, with its peculiar structural type, and on the other the Basin Range pro\ance extends southward through Arizona to New Mexico and Mexico. Between the.ranges are smooth vallejs, whose alluvial slopes and floors are built of the dc'bris washed through many ages from the mountains. In general they are trough-like, but in places they coalesce and assume the character of plains. The plains occupy in general the less elevated regions, where an exceptional amount of detritus has been accumulated. In the local terminology they are called deserts. The largest are the Great Salt Lake and Carson deserts at the north and the Mojave and Colorado deserts at the south. The Escalante, the SeA-ier, the Amargosa, and the Ralston are of subordinate importance. Where the basin is broadest, the general elevation of its lowlands is about 5,000 feet, but they are somewhat higher midway between the eastern and western margins, so as to separate two areas of relative depression, the • eastern marked by the Great Salt Lake and Sevier deserts, and the western by the Carson desert. Southward there is a gradual and irregular descent to about sea-level, and limited areas in Death Valley and Coahuila Valley lie lower thnn the surface of the ocean. The aridity of the region is shown instrumentally by the records of rainfall and atmospheric humidity. On the broad plain bounded east and west by the Appalachian Mountains and the Mississippi River, 43 inches of of rain falls in a year. On the lowlands of the" Great Basin there falls but 7 inches^ In the former region the average moisture content of the air is 69 per cent of that necessary for saturation; in the lowlands of the Great U S.GrOLGOICAL SUp-.-SY LArJE B CK.'CE'.TXE FL. H -^t:.!* :^A..lx; X... ..-4 ( \7 i I 1 I ,-^ :c^' ^^-^^^ZZL I --urn- 1 i,tu; FN D yn.ili-rnftryl.akfs iiiiiurtp|jf>tl L— , .A^iiij-Dxiniale dillu .^■"* Juliu« birn & (u.lilh THE GREAT J^ASIX AM) ITS LAKES CLIMATE OF THE GREAT BASIN. 7 Basin it is 45 per cent.* From the siu-face of Lake Michigan evaporation re- moves each year a layer of water 22 inches deep.^ The -nriter has estimated that 80 inclies are yeai'ly thus removed from Great Sah Lake,^ and Mr. Thomas Russell has com])uted from annual means of temperature, vapor tension, and wind velocity that in the lowlands of the Great Basin the an- nual rate of evaporation froin water surfaces ranges from GO inclies at the north to 150 inches at the south.* The variation with latitude exhibited by the evai)oration is found also, inversely, in the rainfall, but is not clearly apparent in the humidity. In the southern third of the Basin the lowland rainfall ranges fi-om 2 to 5 inches. On the line of the Centi-al Pacific Railroad, between the 40th and 42d par- allels, it averages 7 inches; in the Oregonian ai-m at the north, 15 inches. Tlie average lowland precipitation for the whole -area is betAveen 6 and 7 inches. With the relative humidity approximately constant, the evapora- tion rate varies directly and the rainfall inversely with the temperatm-e, and both latitude and altitude here make the lowland temjjerature fall toward the north. The sj-mpathy of rainfall with temperatui-e is likewise shown in the greater precipitation of the mountains as compared with adjacent vallevs. Mountain stations proper are wanting, but rain-gauge records on the flanks and in the passes of mountains show a marked advantage over those in neighboring lowlands. An estimate based on these, on the records at hio-h points in the Sien-a Nevada, and on aj^proximate knowledge of the heights and areas of the mountains and plateaus of the Great Basin, places the average precipitation for the whole district at 10 inches. The story of climate is more eloquently told by the hydi-ographv and the vegetation. In the valleys of the northwestern ann of the basin there arc numerous lakes, di-aiuless and of varying extent, but fed by streams fi-om momitain ranges of moderate size. In the middle region the onlv per- ennial lakes are associated Avith mountain masses of the fij-st rank. The 'Tbese figures and tbose in the preceding sentences are based on data compiled by tbe U. S. Sig- nal Service. Tbrough the conrtesy of Gen. A. W. Greely, Chief Signal OfiBcer, the writer has had access to manuscript data as well as printed. *D. Farrand Henry, iu a report on tbe meteorology of the Laurentian lakes. Rept. of Chief of Engineers for tbe year ISCS. Washington, l!^9, p. 960. . 'Report on the lands of the Arid Region ■; . . , J. W. Powell, 2d ed., Washington, 1879, p. 73. *MS. report to the Chief Signal Officer. 8 LAKE BONISTEVILLE. great Sierra forming the western wall of the basin receives each winter a heavy coating of snow — the greater part on the side of the great Californian vallev, but enough east of the water-jiarting to maintain a line of lakes in the marginal valleys of the Great Basin. The "Wasatch range and its asso- ciated plateaus, overlooking the Basin fi-om the east, are less favored than the Sierra, but still receive an important precipitation, and by gathering the drainage from a large area, support Great Salt Lake, the largest of the Ba- sin's water sheets. The East Humboldt Range, standing midway, and one of the .largest mountain masses within the basin area, catches enough moist- ure to feed at one base two small lakes and at the other the Humboldt River. The neighboring and smaller mountains are whitened every winter by snow, a large share of which either evaporates without melting or, if melted, is absorbed by the soil, to be returned to the thirsty air Avithout gathering in di-ainage ways. Many of them are without perennial streams; ■ some even lack springs; and of the mountain creeks, few are strong enough to reach the valleys before succumbing to the ravenous desert air. The Humboldt itself, though fairly entitled to the name of river, d\A-indles as it goes, so that its remnant after a course of two hundred miles is able to sus- tain an evaporation lake barely tAventy-five square miles in extent. Most of the small closed basins are without pennanent creek or lake, containing at the lowest point a plava or "alkali flat" — a bare, level floor of fine saline earth, or perhaps of salt, over which a few inches of water gather in time of storm. In the southern half of the Basin there are no lakes dependent for their water on the interior ranges. At the east the most southerly lake is Sevier, in latitude 39°; the last of the lakes sustained by the Sierra is Owens, be- tween the 36th and 37th parallels. Then for tlnee hundred miles evapora- tion is supreme. Playas abound, streams are alniost unknown, and springs are rare. Death Valley, with its floor of salt spread lower than the surface of the ocean, is overlooked on either side by mountains from 5,000 to 10,000 feet high, but they yield it no flowing stream, and more than one traveler has perished from thirst while endeavoring to pass from spring to spring. The Mohave "river" is a hundred miles long, but it preserves its life only by concealment, creeping through the gravel of the desert and betraying CLOUD-BURST CHANNELS. 9 its existence only where ledges of rook athwart its course force it to the surface. • As in other desert regions, precipitation here results only from cyclonic disturbance, either broad or local, is extremely iiregular, and is often vio- lent. Sooner or later the "cloud-burst" visits every tract, and when it comes the local drainage-way discharges in a few hom-s more water than is yielded to it by the ordinary precipitation of many years. The deluge scours out a chainiel which is far too deep and broad for ordinary needs and which centui'ies may not suffice to efface. The abundance of these trenches, in various stages of obliteration, but all manifestly unsuited to the every-day conditions of the countrv, has naturallv led manv to believe that an asre of excessive rainfoll has but just ceased — an opinion not rarely advanced by travelers in other arid regions. So far as mav be judged from the size of the channels draining small catchment basins, the rare, brief, paroxysmal pi-ecipitation of the desert is at least equal while it lasts to the rainfall of the fertile plain. A line of cottonwoods marks the course of each living: stream, but otherwise the lowlands are treeless. So are most of the alluvial foot-slopes and some of the smaller mountains, especially at the south. Except on the high plateaus in central Utah, there is little that may be called forest. The greater mountains have much timber in their recesses, but are not clothed with tiees. Tlie growth is so irregular and interrupted that the idea of a tree limit could not have originated here, but it may be said that only the straggling liush-like cedar passes below G,000 feet at the north or 7,000 feet at the south. Only conifers are of such size and abundance as to have economic importance. Oak and maple gi'ow commonlv as bushes, forming low thickets, but occasionally rank as small trees, along with the rarer box- elder, ash, locust, and hackbcn-y. The characteristic covering of the low- lands is a si)arse growth of low liushes, between wliicli the earth is bare, excepting scattered tufts of gi-ass. Toward the north, and especially on the higher plains, the grass is naturally more abundant and the bushes occupy less space, but the introduction of domestic herds favors the ascendency of the bushes. At the south the bushes are partly of different species, and they are partially replaced by cactuses and other thorny plants. The plavas are 10 LAKE BONXEVILLE. bare of all vegetation and are usually margined by a growth of salt-lo^^ng shrubs and grasses. A single southern bjish bears leaves of deep green, but with this exception the desert plants are grey, like the desert soil. These, and the persistent haze w'hose grey veil deadens all the landscape, weary' the eye with their monoton}-, so that the A-ivid green marking the distant spi-ing is welcome for its own sake as well as for the promise of refre.slmient to the thirsty traveler. The causes of this arid climate lie in the general circulation of tlie atmosphere, in the ciuTents of the Pacific Ocean, and in the configuration of the land. There is a slow aerial drift from west to east, so that the air coming to the Basin has previously traversed a portion of the Pacific, to which its temperature and humidity have Ijecome adjusted. Off the west coast of the United States there is a southward current, believed to be the chief branch of the Kuro Siwa. Prof George Davidson^ estimates its width at about 300 miles, and finds that its temperature rises with southward advance only one degree Fahrenheit for each degree of latitude. Being derived from a n<:>rth-moving current, it reaches our coast with a tempera- ture higher than that normal to the latitude, while at the south its tempera- ture is below the normal. As pointed out by Button,^ the air passing from it to the land at the north is cooled by the land and precijjitates moistui-e, while the similar air-cm-rent at the south is wanned by the land and con- veiiied to a drpng wind. The Great Basin falls Avithiu the influence of the drpng wind, its southern part being more affected than its northern. At the extreme south and the extreme north the mountains between the ocean and the Basin do not greatly interfere Avith the eastward flow of air, but between latitudes 35° and 41° the Sierra Nevada forms a continuous wall, rarely less than ten thousand feet high. In rising to pass this obstruction the air loses much of its stored moisture, especially in winter, and it descends to the Basin with diminished humidity. The Basin is further influenced by deAnations of the air-currents from the eastward direction, and its southern part falls in summer within the zone of calms'theoretically due to a descending current at the" margin of the northern trade-wind; but observational data are too meager for the discussion of these factors. 'Letter to the writer. * Cause of the Arid Climate of the westerD portion of the U. S., Capt. C. E. Dntton : Am. Jonr. ' 8ci., 3d ser., vol. 22, p. 249. OTHEE rs^TERIOR BASINS. H Tlie southern poi-tions of Arizona and New Mexico and the western part of Texas resemble the Great Basin in climate, and they contain a nmnber of small interior basins. These are not so fnll)' detennined in extent as the Great Basin, but several of them may be approximately indicated. One of the largest lies between the Rio Grande and its eastern branch, the Pecos, extending from latitude 35° in central New I^Iexico to latitude 31° in west- ern Texas. In its broadest part it is bounded on the west by the San An- di"eas and Organ Mountains, and on the east by the Sacramento and Guada- loupe. Its area, of which two-thirds lies in New Mexico, is about 12,500 square miles. Southwest of the Kio Grande, in Mexico, there is a larger tract of interior drainage, containing a number of saline lakes, and to one of these, Lake Guzman, the valley of the Mimbres River of New Mexico descends. Other basins adjacent on either side to that of the Mimbres are believed to bear the same relation to Lake Guzman, sloping gently toward it, but contributing no water ludess during periods of rare and exceptional storm. Ye.t other basins A\-ithout exterior drainage are contiguous to these, and unite to form in soutlnvestcrn New Mexico an arm of the Mexican district of interior drainage, the area within New Mexico probablv falling between 7,000 and 7,500 square miles. North of this, and intersected cen- trally by the 103d meridian and the 34th parallel, lies a smaller basin, includ- ing the plain of San Augustin. Its area is about 1,800 square miles. In southeastern Arizona a slightly smaller basin lies between the Caliyuro and Dragoon M(iuntains on the west and the Pinaleno and Chiricahua Mount- ains on the east, including the Playa de los Pimas. Another and still smaller basin is known to exist in the Hualapi Valley of northwestern Arizona, and it is probable that others occur in the western part of the Territorv, both north and south of the Gila River. When all have been determined and measured, it is estimated that the total area of the interior basins of the LTnited States, additional to the Great Basin, Avill be found equal to 25,000 squai-e miles, making the grand total for the United States about 232,000 square miles — the thirteenth part of our territory. Mexico contains other inland districts besides the one mentioned above, and the total area in that country may be one-third as great as om-s. It is probable that the remainder of the continent di-aius to the ocean. 12 LAKE BONNEVILLE. Large as are these districts, it is nevertheless true that North America, as comiDared with other continents, is not -characterized by interior drainage. According to data compiled by Mun-ay, the closed basins in Australia aggre- gate 52 per cent of its area, those of Africa 31 per cent, of Eurasia 28 per cent, of South America 7.2 per cent, of Korth America 3.2 per cent.^ The Great Basin is gi-eat only in comparison with similar districts of our own continent. The interior district of the Argentine Republic and Bolivia is half as large ajrain, and that of central Australia exceeds the Great Basin seven times; Sahara exceeds it sixteen times, and the interior district of Asia twenty-three times. HISTORY OF INVESTIGATION. The history of the early geographic exploration of the Great Basin has been carefully detailed by Simpson in the introduction to the report of his own expedition. In 177G it was penetrated by Padi-e Escalante from the southeast, and about the same time its southern rim was crossed by Padre Graces, but it does not appear that they discovered the peculiarity of its drainage. From about 1820 to 1835 the northern and broader portion of the basin was gradually explored by Indian-traders, who learned of the existence of undrained lakes and passed the account from mouth to mouth, but made no maj^s and published no accounts of their discoveries. Capt. • Bonneville, an army officer on leave, ti-aveling in the interest of the fur trade but with the spirit of exploration, took notes of geographic value (1833), which Avere put in shape and published after a lapse of some years by Washington Ii-ving, and his map is probably the first which represents interior drainage. While Irving's account was in press, Fremont was en- gaged in his justly celebrated exploration which affitrded to the world the first clear conception of the hj'ch-ogi-aphy of the region.^ Since that time numerous expeditions, public and private, have contributed details, so that now the external boundary of the Great Basin is well known except at the extreme south, and its internal configuration has been described and mapped throughout four-fifths of its extent. ■ The total annnal rainfall of the land of the globe, and the relation of rainfall to the aanaal dis- charge of rivers. By John Murray. Scottish Geog. Mag. vol :i, pi>. 65-77. 'Report of the Exploring Expedition to the Rocky Mountains in the year 1842 and to Oregon and North California in the years lS43-'44. by Brevet-Capt. J. C. Fremont. Washington, 1845. STAXSBDRY ON ANCIENT SHORES. 13 Our knowledge of that lacustrine history to which the present volume is a contribution begins with Stansbury. Fremont, finding a line of tb-ift- wood a few feet above the water of Great Salt Lake, inferred a small varia- tion of its level, but ajipears to have overlooked the ancient shore-lines ter- -^ racing the mountains round about. He described the coating of tufa on the A-allev sides near Pyramid Lake, and the thought that it might be a lacust- rine deposit occurred to him, but was deemed inadmissible on account of the thickness of the formation. Stansbury in 1849 and 1850 made an elaborate survey of Great Salt Lake and its ^^cinity, meandering its shore, determining its depth by a series of soundino-s, and controllinjj his work by a system of trianffulatioii. In his itinerary, while describing the plain where now stands Lakeside station of the Central Pacific railway, he says: This extensive flat appears to liave formed, at one time, the northern portion of the lake, for it is now but slightly above its present level. Upon the slope of a ridge connected with this plain, thirteen distinct successive benches, or water-marks, were counted, which had evidently, at one time, been washed bj the lake, and must have been the result of its action continued for some time at each level. The highest of these is now about two hundred feet above the valley, which has itself been left by the lake, owing jirobably to gradual elevation occasioned by subterraneous causes. If this supposition be correct, and all appearances conspire to support it, there must have been here at some former period a vast inland sea, extending for hundreds of miles; and the isolated mountains which now tower from the flats, forming its western and southwestern shores, were doubtless huge islands similar to those which now rise from the diminished waters of the lake.' One of liis sketches of Fremont Island, reproduced in a lithograph facing page 102 of his report, exliibits teiTaces of the same sort, and he says in another place that the island, which is "at least 800 or 900 feet high," presented "the appearance of regular beaches, bounded by what seemed to have been well-defined and perfectly horizontal water-lines, at different heights above each other, as if the water had settled at intervals to a lower level, lea^■ing the marks of its former elevation distinctly traced upon the hillside. This continued nearly to the summit, and was most apparent on tlie northeastern side of the island." - 'Exploration and Survey of the Valley of the Great Salt Lake of Utah, .... by Howard Stans- bury, Capt. Top. Eng., Philadelphia, 1852, p. 105. « Ibid. p. 160. 14 LAKE BONNEVILLE. Beckwith, who led a geographic expedition across the Great Basin in 1854, makes the next advance in the description of the lacustrine phenom- ena, and his contribution is so imjjortant that I quote it entire: The old sboreliues existing in tbe vicinity of tbe Great Salt Lake present au interesting study. Some of tbeni are elevated but a few feet (from five to twenty) above the present level of tbe lake, and are as distinct and as well deJiiied and pre- served as its present beaches; and Stansbiirj speaks, in the Ileport of his exploratiuu, pages 158-lGO, of driftwood still existing upon those having au elevation of five feet above the lake, which unmistakably indicates the remarkably recent recession of tbe waters which formed them, whilst their magnitude and smoothly-worn forms as unmis- takably indicate tbe levels which the waters maintained, at their respective forma- tions, for very considerable periods. In the Tuilla Valley, at the south end of the lake, they are so remarkably distinct and peculiar in form and position that one of them, on which we traveled in crossing that vallej- on the 7tb of May, attracted the observation of the least informed team- sters of our party — to whom it appeared artificial. Its elevation we judged to be twenty feet above tbe present level of the lake. It is also twelve or fifteen feet above tbe plain to the south of it, and is several miles long; but it is narrow, only aflording a fine roadway, and is crescent-formed, and terminates to tbe west as though it had once formed a cape, projecting into the lake from the mountains on the east — in miniature, perhaps, not unlike tbe strip of laud dividing the sea of Azofl" from the Putrid sea. From this beach the Tuilla Valley ascends gradually towards the south, and in a few miles becomes partly blocked up by a cross-range of mountaius, with passages at either end, however, leading over quite as remarkable beaches into what is known, to tbe Mormons, as Rush Valley, iu which there are still small lakes or ponds, once, doubt- less, forming part of the Great Salt Lake. The recessions of the waters of the lake from tbe beaches at these comparatively slight elevations, took place, beyond all doubt, within a very modern geological period; and the volume of the water of tbe lake at each subsidence — by whatever cause pro- duced, and whether by gradual or spasmodic action — seems as plainly to have been diminished; for its present volume is not sufficient to form a lake of even two or three feet in depth, over the area indicated by these shores, and, if existing, would be annu- ally dried up during the summer. These banks — which so clearly seem to have been formed and left dry within a period so recent that it wouhl seem impossible for the waters which formed them to have escaped into the sea, either by great convulsions, oi)euiiig passages for them, or by tbe gradual breaking of the distant shore (rim of the Basin) and draining them ofif, without liaving left abundant records of the escaping waters, as legible at least as the old shores they formed — are not peculiar to the vicinity of this lake of the Basin,, but were observed near the lakes in Franklin Valley, and will probably be found near other lakes, and iu the numerous small basins which, united, form the Great Basin. But high above these diminutive banks of recent date, on the mountains to tbe east, south and west, and on tbe islands of the Gieat Salt Lake, formations are seen, preserving, apparently, a uniform elevation as far as tbe eye can extend — formations BECKWITH OX ANCIENT SHOEES. 15 on a magnificent scale, whicb, hastily examined, seem no less nnmistftkably tliau the foriuei to iudicate their shore origin. They are elevated from two or three hundred to six or eight hundred feet above the present lake; and if upon a thorough examination they prove to be ancient shores, they will perhaps afford (being easily traced on the numerous mountains of the Basin) the means of determining the character of the sea by which they were formed, whether an internal one, subsequently drained off by the breaking or wearing away of the rim of the Basin — of the existence of which at any time, in the form of continnons elevated mountain chains, there seems at present but little ground for believing — or an arm of the main sea, which, with the continent, has been elevated to its present positron, and drained by the successive stages indicated by these shores.' A year earlier Blake explored the Colorado desert between Sau Diego and Fort Yuma, finding unmistakable e^■idenc•e of its former occupation l)v a lake. He observed a shore line, tufa deposits, and lacustrine clays, and in the clays and tufa, as well as scattered over the surface of the desert, he found fresh-water shells, and a single brackish shell, Gnathodon. His de- scription and discussion are full and eminentlv satisfactory, but his expla- nation takes the lake he describes out of the field of present interest, for he shows that only its disappearance and not its origin is to be ascribed to climate. The lake basin was created by the growth of the delta of the Col- orado River, which was built across tlie Gulf of California, separating a portion of its upper end.. "\Mien the river, shifting on its delta, is turned to the right, a lake is maintained behind the barrier, a lake with outlet to the Gulf, and therefore fresh. A^Hien the river turns to the left, it flows directly to the Gulf, and the lake is dried away. The latter is the present and liis- toric condition, but occasionally at extreme flood a jDortion of the river's water has been known to flow for many miles toward the desiccated basin.^ Simpson, exploring for wagon routes in the broadest part of the Great Basin, in 1859,' observed in Cedar and Rush valle3-s the same water lines that had been seen by Stansbury farther north; and Henry Engelmann, the geologist of his party, noted not only shore terraces btit' lacustrine silt and tufa and fresh-water shells. He points out that the saltness of the 'Explorations . . . from the mouth of the Kansas River, Mo., to the Sevier Lake, in the Great Basin. By Lieut. E. G. Beckwith. Foot note to )). 97. lu Pacific Railroad reports, vol. 2, Washing- ton, l^S.^. ' Geological Report, by William P. Blake. In Pacific Railway Reports, vol. 5, 1656, pp. 97-99, 236-239. 'Explorations across the Great Basin of the Territory of ITtah for a direci wagon-route from Camp Floyd to Genoa, in Carson Valley, iu 1659, by Captain J. H. Simpson. Washington, 1876. 16 LAKE BOXNEYILLE. Basin lakes is inconsistent with the prevalent impression that they possess subterranean outlets, and compaiing their former with their present extent, refers the difference to climate. He argues that the present geographic con- ditions tend to the diminution of rainfall, and that under them the ^jasiu has become progressively more and more arid. But there is nothing in his dis- cussion serving to explain the greater humidity of tlie preceding age. The reports of Simpson and Engelmann, though prejjared in manu- script immediately after the completion of their exploration, were not printed until 1878, and in the mean time many observers saw the lake vestiges and wrote upon them. "\ATiitney, visiting Mono Lake in 1863, and noticing old shore-lines rising in a series to the height of GOO feet above the water, raised the question — for many years unanswered — whether the old lake was con- fined to the Mono Valley or communicated with lakes in other valleys of the Great Basin, and pointed out that Avhatever conditions produced the ancient glaciers of the adjacent Sierra were competent to expand the lake.* Hay- den in 1870 examined the old shore-lines in the immediate ^-icinity of Great Salt Lake, coiTCCtly correlated them Avith lacustrine deposits at various points, showed their recency as compared to the later Tertiary beds of the vicinity, and referred them to the Quaternary. He also found shells in the deposits, and from their character recognized the fi-eshness of the old lake.^ Bradley, two years later, recognized the broad teiTaces flanking Ogden River and other streams of the A-icinity as deltas built by the same streams in the ancient lake, observed that the Ogden delta deposits extended into the mountain canyon of the river, and drew the important conclusion that before the age of the high terraces Great Salt Lake was not far, if at all, above its present level.' About the same time Poole made additional obser- vations on the shore-lines of the same basin and traced them as far westward as the Deep Creek Mountains.* The obserA-ations of Hayden, Bradley, and Poole were independent and original, and by reason of priority of publication they belong to the 'Geol.Surv. of California, Geology, vol. 1, by J. D. Wbituey. PLiladclpbia 1865, pi>. 451-452. «U. S. Geol. Surv. of Wyomiug. . . 1670, by F. V. Hayden. Washington, 1872, pp. 169, 170, 172, 175. 5 Report of Frank H. Bradley, in U. S. Geol. Surv. of the Territories, Kept, for 1872. Washing- ton, 1873, pp. 192, 196. eriod, rank- ing with the Eocene period. It is generally believed that the Pleistocene is comparable in point of duration with one of the periods of the Tertiary era, being less rather than greater, and those who advocate the ■emplo}Tnent of the name Quaternary recognize the Quaternary era as one containing but a single period. The time division with Avhich we have to deal is, then, from every point of \dew, a "period," and it is believed that the use of the name Pleistocene Period involves a minimum amount of implication as to higher classification, a subject whose discussion is not here contemplated. CHAPTER II. THE TOPOGRAPHIC FEATURES OF LAKE SHORES. It has been assumed in the preceding pages that valleys from which lakes have recently disajijieared are characterized by certain features whereby that fact can be recognized. Perhaps no one observant of natural phenomena will dispute this. But there is, nevertheless, some diversity of ojjiuion as to what are the peculiar characters to which lakes give rise; and especially has the true interpretation of certain local topographic features been mooted, some geologists ascribing them to waves, and others to dif- ferent agencies. In the investigation of our ancient lake, it has been found necessary not only to discriminate from all other topographic elements the features created by its waves, but also to ascertain the manner in which each was produced, so as to be able to give it the proper interpretation in the recon- struction of the history of the lake. It is proposed in tliis chapter to pre- sent the more general results of this study, describing in detail the various elements which constitute shore topography, explaining their origin, so far as possible, and finally contrasting them with topographic features of other origin which so far simulate them as to occasion confusion. The play of meteoric agents on the surface of the land is unremitting, so that there is a constant tendency to .he production of the forms charac- teristic of then- action. All other fomis are of the nature of exceptions, and attract the attention of the observer as requiring explanation. The shapes wrought by atmospheric erosion are simple and sjTnmetric and need but to be enumerated to be recognized as normal elements of the sculpture 23 24 LAKE BONXE\^ILLE. of the land. Along each drainage line there is a gi'adual and gi-adually increasing ascent from mouth to source; and this law of mcreasing acclivity applies to all branches as well as to the main stem. Between each pair of adjacent drainage lines is a ridge or hill, standing midway and rounded at the top. Wherever two ridges join there is a sunnnit higher than the adja- cent portion of either ridge; and the highest summits of all are those which, measming along lines of drainage, are most remote from the ocean. The crests of the ridges are not horizontal but undulate from summit to summit. There are no sharp contrasts of slope; the concave profiles of the drainage lines change their inclination little by little and merge by a gradual transi- tion in the convex profiles of the crests and summits. Tlie factor which most frequently, and in fact ahnost universally, inter- rupts these simple curves is heterogeneity of terrane. Under i;u.' influence of. this factor, just as in the case of a homogeneous ten-ane, the declivities adjust themselves in such way as to oppose a maximum resistance to erosion; and with diversity of rock texture tliis adjustment involves diversity of fonn. Hard rocks sur^•ive, while the soft are eaten away. Peaks and cliff's are produced. The apices are often angular instead of roi;nded. Profiles exhibit abiiipt changes of slope. Flat-topped ridges ajipear, and the dis- tribution of maximum summits becomes in a measure independent of the length of di-ainao^e lines. A second factor interrupting the continuity of erosion profiles is up- heaval; and this produces its eff"ects in two distinct ways. First, the general uprising of a broad ti-act of land aifects the relation of the drainage to its point of discharge or to its base level, causing coirasion by streams to be more rapid than the general waste of the surface and producing canyons and terraces. Second, a local upri.siug by means of a fault produces a €115" at the margin of the uplifted ti'act; and above this cliff' there is sometimes a terrace. A third disturbing factor is glaciation, the cirques and moraines of which are distinct from anything WTOught by plu^^al erosion; and a fourth is found in eruption. The products of all these agencies except the last have been occasionally confused with the phenomena of shores. The beach-lines of Glen Roy have SCULPTURE OF THE LAND. 25 been called river teiTaces and moraine terraces. The cliffs of the Downs of England have been ascribed to shore waves. Glacial moraines in New Zealand have been interpreted as shore ten-aces. Beach ridges in our own country have been described as glacial moraines, and fault terraces as well as river terraces have been mistaken for shore-marks. In the planning of engineering works for the improvement and protec- tion of harbors, it is of prime importance to understand the natm-al processes by which coast featm-es are produced and modified, and this necessity has led to the production by engineers of a large tjiough widely scattered litera- tuj-e on coast-forming agencies. Geologists also requii-e for the interpre- tation of strata originating as coast deposits an understanding of the methods of coastal degradation and coastal deposition, and from their point of vieAV there has arisen an independent literature on the subject. The physical theory of water waves required alike bv engineers and geologists has been developed by pliysicists, and has its own literature. The three groups of writers have so thoroughly traversed the subject of shore processes that the present chapter would have need to demonstrate its raison d'etre were it not that the general subject has as yet received no compendious and systematic treatment in the English langfua^e. It happens, moreover, that the present treatment of the subject has its own peculiar point of view, and is in large part independent. During the progress of the field investigation I was unaware of the greater part of the literature mentioned above, having indeed met with but one important paper, that in which Andi-ews describes the fonnation of beaches at the head of Lake Michigan, and I was induced by the requirements of my work to develop the philosophy of the subject ab initio. The theories here presented had therefore received approximately their present form and arrangement before they were compared with those of earlier writers. They are thus original ■s%'ithout being novel, and their independence gives them confirma- tory value so far as they agree with the conclusions of others. The peculiarity of the point of view lies in the f\ict that the phenomena chiefly studied are fossil shore-lines instead of modem. The bodies of wjter to which they pertain ha\-ing disappeared, the configuration of the sub- merged portion is dii-ectly seen instead of being interpreted from laborious 26 LAKE BONNEVILLE. soundings. There are, iporeover, natural sections of the deposits, exposed by subsequent erosion, and these reveal features of internal structure or anatomy quite as important to the geologist a.s tlie features of mori)hology. The literature of sliore-lines is so feebly connected by cross reference, and portions of it have been discovered in places so unexpected, that the writer fears many important contributions have escaped his attention. Within the range of his reading, the earliest discussions of value are Ijy Beaumont^ and De la Beche,- and it must be admitted that the writers of geologic manuals now in use liave iniproved ver^ little upon their presentation. Fleming, in an essay on the origin and preservation of the harbor of Toronto,^ set forth the process of littoral transportation with admiral )le clearness; and Andrews, who appears to have reached his conclusions by independent observation, added to the theory <>f littoral transportation an important factor in the theory of littoral deposition." Mitchell, in an essay on tidal marshes,^ inci- dentally describes the growth of the protecting barrier. A general treatise by Cialdi" gives a systematic discussion of coast processes from the engi- neer's pouit of view, and reAnews the Italian literature of the subject; and a shorter paper by Keller' has a similar scope. Richthofen, in his manual of instruction to scientific travelers, treats analytically and at length of the work of waves in conjunction Avith tides, and discusses a subsiding conti- nent* The theory of waves has been developed experimentally by a com- mittee of the British Association, with J. Scott Russell as reporter;' and it is analytically treated by Airy" and Rankine." ' Lefons de geologic pratique. Par Elie de Beaumont. Vol. 1, pp. 221-253, Paris, 1845. 'A Geological Mauual. By Heury T. De la Beche. 3d edition, enlarged, Loudon, 1833, pp. (17-91. Tbo Geological Observer. By the same. London, 1851, pp. 49-117. 'Toronto Harbor— its formation and preservation. By Saudford Fleming, C. E. : Canadian Journal, vol. 2, 1854, pp. 103-107, 223-230. Repriuted with additions as Report on Preservation, and Ini|>rovement of Toronto Harbor. In Suppleitent to Canadian Journal, 1854, pj). 15-29. lete. Under conditions not yet apparent, and in a manner equally obscure, there is a rhj^hmic action along a certain zone of the bottom. That zone lies lower than the trough between the greatest stonn waves, but the water upon it is violently oscil- >Geol. Hist, of Lake Labontan. pp. 92-93. 46 LAKE BONNEVILLE. lated by the passing waves. The same water is translated lakeward by the undertow, and the surface water above it is translated landward by the viind, while both move with the shore current parallel to the beach. The rhythm may be assmned to arise from the interaction of the oscillation, the land- ward cmTent, and the undertow. LITTORAL DEPOSITION. Tlie material deposited by shore jorocesses is, first, shore di-ift ; second, stream drift, or the detritus delivered at th^ shoi-e by tributary streams Increasing dei)th of water is in each case the condition of littoral deposi- tion. The structures produced by the deposit of shore drift, although some- what varied, have certain connuon features. They will be treated under the generic title of emhankmcnts. The structures produced by the deposit of stream drift are deltas. EMBANKMENTS. The current occupjnng the zone of the shore drift and acting as the coagcnt of littoral transportation has been described as slow, but it is insepa- rably connected with a movement that is relatively rapid. This latter, which may be called the off-shore cmTent, occupies deeper water and is less impeded by friction. It may in some sense be said to di-ag the littoral cuiTent along with it. The momenttun of the off-shore cuirent does not peiTnit it to fol- low the sinuosities of the Avater margin, and it sweeps from point to point, can-ying the littoral current with it. There is even a tendency to generate* eddies or return currents in embayments of the coast. The off-shore cur- rent is moreover controlled in part by the configuration of the bottom and by the necessity of a return current. The littoral cmTent, being controlled in large part by the movements of the off-shore current, separates from the water margin in three ways: first, it continues its direction unchanged at points where the shore-line turns landward, as at the entrances of bays ; sec- ond, it sometimes turns from the land as a surface cuiTent; third, it some- times descends and leaves the water margin as a bottom current. In each of these tlu'ee cases deposition of shore di-ift takes jilace by reason of the divorce of shore cmTents and wave action. The depth to THE GENESIS OF SPITS. 47 which wave agitation sufficient for the transportation of shore chift extends is small, and when the littoral current by leaving the shore passes into deeper waters the shore dinft, unable to follow, is thrown down. Wlien the current holds its direction and the shore-line diverges, the embankment takes the fonn of a sjnt, a hook, a bar, or a looj). When the shore-line holds its course and the cun-ent diverges, whether superficially or by descent, the embankment usually takes the form of a terrace. The spit.-WTien a coast line followed by a littoral cm-rent turns abruptly landward, as at the entrance of a bay, the cm-rent does not turn with it, but holds its com-se and passes from shallow to deeper water. The water be- tween the diverging current and coast is relatively still, although there is communicated to the portion adjacent to the current a slow motion in the same direction. The waves are propagated indifferently through the flow- ing and the standing water, and reach the coast at all points. The shore di-ift can not follow the deflected coast line, because the waves that beat against it ar»i unaccompanied by a httoral current. It can not follow the littoral current mto deep water, because at the bottom of the deep water there is not sufficient agitation to move it. It therefore stops. But the supply of shore di-ift brought to this point by the littoral current does not cease, and the necessary result is accumulation. The particles are can-ied forward to the edge of the deep water and there let fall. In this way an embankment is constructed, and so far as it is built it serves as a road for the transportation of more shore di-ift. The direction in which it is built is that of the littoral cun-ent. It takes the form of a ridge following the boundary between the current and the still water. Its initial height brings it just near enough to the surface of the Avater to enable the wave agitation to move the particles of which it is consti-ucted; and it is naiTOw. But these characters are not long maintained. The causes which lead to the constniction of the beach and the barrier are here equally efficient, and cause the embankment to grow in breadth and in height until the cross-profile of its upper surface is identical with that of the beach. The liistory of its growth is readily deduced from the configuration of its terminus, for the process of growth is there in progress. If tlie matei-ial is coarse the distal portion is very slightly submerged, and is terminated in 48 LAKE BONNEVILLE. the direction of growth by a steep slope, the subaqueous "earth-slope" of the particular material. If the mateiial is fiue the distal portion is more deeply submerged, and is not so abruptly terminated. The portion above water is usually naiTOw tlu-oughout, and terminates without reaching tlie extrem- ity^ of the embankment. It is flanked on the lakeward side by a submerged plateau, at the outer edge of which the descent is somewhat steep. The profile of the plateau is that nonnal to the beach, and its contours are con- fluent with those of the beach or barrier on the main sliore. Toward the end of the embankment its width diminishes, its outer and limiting contour turning toward the crest line of the .spit and finally joining it at the sub- merged extremity. Tlie process of construction is similar to that of a railroad embankment the material for which is derived from an adjacent cutting, carted forward along the crest of the embankment and dumped off" at the end; and the sym- metry of form is often more perfect than the railway engineer ever accom- plishes. The resemblance to railway structures is very striking in the case of the shores of extinct lakes. As the embankment is carried forward and completed, contact between the cuiTent and the inshore water is at first obstructed and finally cut off", so that there is practically no communication of movement from one to the other at the extremity of the spit. At the point of constniction the moving and the standing water are sharply diff"erentiated, and there is hence no uncertainty as to the direction of construction. The spit not only follows the line between the cmTent and still water, but aids in gi^*ing definition to that line, and eventually walls in the current by contom's adjusted to its natural flow. The Bar.-If thc cun'eut detenuiniug the fonnation of a spit again touches the shore, the construction of the embankment is continued until it spans the entire interval. So long as one end remains free the vernacular of the coast calls it a sj>?7; but when it is completed it becomes a bar. Figure 7 gives an ideal cross-section of a completed embankment. Tlie bar has all the characters of the spit except those of the terminal end. Its cross-profile shows a plateau bomided on either hand by a steep slope. The surface of the plateau is not level, but has the beach profile, is ^irw B, O) t^^- mm 1 1 BARS AT THE MOUTHS OF RIVERS. 49 slightly submerged on the wiudward side and rises somewhat above the ordinary water level at the leeward margiu. At each eud it is continuous with a beach or barrier. It receives shore drift at one end and deli\ers it at the other. The bar may connect an island witli the shore or with another island, or it ' r,o. 7.-sec.io„ „f a L>.ear Emb.nk„,c.ut. may connect two portions of the same shore. In the last case it crosses the mouth either of a bay or of a ri\er. If maintained entire across the entrance to a bay it converts the Avater be- tween it and the shore into a lagoon. At the mouth of a river its mainte- nance is antagonized bv the outflowing current, and if its inte^ritv is estab- lished at all it is only on rare occasions and for a short time. That is to say, its full height is not maintained; there is no continuous exposed ridge. The shore di'ift is, however, thi-own jnto the river cmTent, and unless that cmTent is sufficient to sweep it into deep water a submerged bar is tlii-own across it, and maintains itself as a partial obstruction to the floAV. The .■ —^"' cussion. In the first place they are not formed by the predomi- nant winds, but by those Avhich bring the greatest waves. The predominant winds are west- erly, and jiroduce no waves on tin scoast. The shore di'ift is de- rived from the south coast, and its motion is first westerly and then northerly. Two bars are ^[ exhibited, the western of •\\hich is now protected from the lake waves, and must have been com- pleted before the eastern was begun. The place of de2)osition of shore drift was ])robably shifted from the Avestern to the eastern by reason of the shoaling of the head of the lake. The converging shores should theoretically produce during easterly storms a powerful undertow, by which a large share of the shore drift would be carried lakeward and distributed over the bottom. The manner in which the bars temiinate against the northern shore without inflection is explica- ble likewise by the theory of a strong undertow. If the return cin-rent Avere superficial the bars would be curved at their junctions Avitli both shores. An instructive -view of an ancient bar will be found in PI. IX, repre- senting a portion of the BonneA-ille shore line. The town of Stockton, Utah, appears at the right. The plain at the left was the bed of the lake. The Fig. 9.— Map of tlie head of Lake Superior, aliowius Bii> liars. 52 LAKE BONNEVILLE. storm waves, mo-sniig' from left to riglit, carved the sea-cliff whicli appears at the base of the mountain at the left, and drifting tlie material toward the right built it into a great spit and a greater bar. The end of the spit is close to the town. The bar, which lies slightly lower, having been formed by the lake at a lower stage of its water, sweeps in a broad curve across the valley to the rocky hill on the opposite side, where the artist stood in making the sketch. The Hook.-Tlie line of direction followed by the spit is usually straight, or has a slight concavity toward the lake. This fonn is a function of the lit- toral current, to which it owes origin. But that current is not perpetual; it exists only during the continuance of certain determining winds. Other winds, though feebler or accompanied by smaller waves, nevei'theless have systems of currents, and these latter currents sometimes modify the form of the spit. Winds which simply reverse the direction of the littoral current retard the construction of the embankment without otherwise affecting it; but a cuiTent is sometimes made to flow past the end of the spit in a direction making a high angle with its axis, and such a current modifies its form. It cuts away a portion of the extremity and rebuilds the material in a smaller spit joining the main one at an angle. If this smaller spit extends lakeward it is demolished by the next storm; but if it extends landward its position is sheltered, and it remains a permanent feature. It not infrequently happens that such accessory spits ai-e formed at intervals during the construction of a long embankment, and are preserved as a series of short branches on the lee side. It may occur also that a spit at a certain stage of its growth becomes especially sul>ject to some confhcting current, so that its normal growth ceases, and all the shore drift transported along it goes to the construction of the branch. The bent embankment thus produced is called a hook. The currents eflicient in the formation of a hook do not cooperate simultaneously, but exercise their functions in alternation. The one, during the prevalence of certain winds, brings the shore drift to the angle and accumulates it • there ; the other, during the prevalence of other winds, de- molishes the new structure and redeposits the material upon the other limb of the hook. mSk' :? IK) Z I .|1 (l':.,;*l' *4 i'WRH''^y ililM ill ' ' M.^' I'' ■ idikiiiiiiiiujiii. '5:1' 'h: HOOKS. 53 In case the land on -uhicli it is based is a slender peninsula or a small island, past whicli the currents incited by various winds sweep with little modification of direction by the local configuration, the hook no longer has the sharp angle due to the action of two currents only, but receives a curved form. Hooks are of comj^ai-atively rare occurrence on lake shores, but abound at the mouths of marine estuanes, where littoral and tidal currents conflict. Plate V represents a recurved spit on the shore of Lake Micliigan, seen from a neighboring bluft'. The general direction of its construction is from left to light, but storms from the right have from time to time turned its end toward the land and the successive recurvements are clearly discernible near the apex. Tlie mole enclosing Toronto harbor on the shore of Lake Ontario is a hook of unusual complexity, and the fact that its growth threatens to close the entrance to the harbor has led to its thorough study by engineers. Especially has its history l)een developed by Fleming in a classic essay to which reference has already been made. A hill of diift projects as a cape from the north shore of the lake. The greatest waves reaching it, those liaving the greatest fetch, are from the east (see Fig. 10), and the cooper- ating current flows from east to west. As the hill gradually yields to the waves, its coarser material trails westward, building a spit. The waves and currents set in mo- ti( m by southwesterly winds cany the spit end nortliAvard, producing a Jiook. In the jiast the westward movement has been the more powerful and the spit has continued to grow in that direction, its north- ern edge being fringed with the sand ridges due to successive recurvements, but the shape of the bottom has introduced a change of conditions. The water at the west end of the spit is now deep, and the extension of the embank- ment is con-espondingly slow. The northward drift, being no longer sub- ject to frequent shifting of position, has cumulative effect on the terminal hook and jjives it a greater lenirth than the others. In the chart of the liar- bor (Fig. 11) the composite cliaracter of the mole is readily traced. It may Fig, 10.— Diajrram of Lake Ontario, to ehow the Fetch of "Waves reailiinj; Toroutofrom liiflereiit directions. 54 LAKE BOH^'EYILLE. also be seen that the ends of the successive hooks are connected by a beach, the •work of waves generated within the harbor by northerly winds.' It will be observed furthermore that while the west end of the spit is continuously fringed by recurved ridges its eastern part is quite free from them. This does not indicate that the spit was simple and unhooked in the early stages of growth, but that its initial ridge has disappeared. As the clift' is eroded, jj^O-N-T O Fig. 11.— Map of the harbor and peniDSula (Hook) at Toronto. From charts publishe3 hy H. T. niml, in 185J.' its position constantly shifts landward, the shore current follows, and the lakeward face of the spit is carried away so that the waves break over it, and then a new crest is built by the waves just back of the line of the old one.' By thi.s process of partial destruction and renewal the spit retreats, keeping pace Avith the retreating cliff. At an earlier stage of the process the spit may have had the position and form indicated by the dotted out- line, but whatever hooks fringed its inner margin have disappeared in the process of retreat. 'The marsh occnpiring part of the space betweeu the spit aud the mainland (Fig. 11) is only incidentally counected with the feature under discussion. A small stream, the Don, reaches the shore of the lake within the tract protected from waves hy the hook and is thus enabled to construct a delta with its sediment. 2 Report on the preservation and improvement of Toronto Harbor. In Supplement to Canadian Journal, 1^54. 'At the present time the spit is divided near the middle, a natural breach having been artificially preTeuted from healing. The portion of the peninsula fringed by successive hooks stands as an island. % ■ % y ''ii' ■•■£ ^ ^ h I" > LOOPED BAES. 55 The landward shifting illustrated by the Toronto hook affects many embankments, but not all. It ordinarily occurs Avhen the embankment is built in deep water and the source of its material is close at hand. Wherever it is known tliat an embankment has at some time been breached by the waves, it may be assumed with confidence tliat retreat is in ])rogress. As retreat progresses the layers constituting the embankment are trun- cated at top, and new layers are added on the land\'\aiil side. In the result- ing structure the prevailing dip is landward (Fig. 12), and it is thei'eby distinguished from all other forms of lacustrine deposition. Tliis structure was first described and explained by Fleming, who obser\'ed it in a railway cutting through an ancient spit.' The Loop.- Just as the spit, by advancing until it rejoins the shore, becomes a bar, so the completed hook niay with propriety be called a hop or a looped har. There is, however, a somewhat different feature to whicli tla- name is more strikingly applicable. A small island standing near tlie niain-lnnd is usually furnished on each side with a spit streaming toward the land. These spits are composed of detritus eroded from the lakeward face of the island, against which beat the waves generated tlu'ough the broad expanse. The currents accompanying the waves are not uniform in direction, but vary with the wind through a wide angle; and the spits, in sympathy with the varying direction of currents, are curved inward toward the island. If their extremities coalesce, they constitute together a perfect loop, resemblingj^ when mapped, a festoon pendent from the sides of the island. Sucli a loop in the fossil condition, tliat is, when preserved as a vestige of the .shore of an extinct lake, has the form of a crater rim, the basin of th.e original lagoon remaining as an undrained hollow. The accompanying illustration (PI. VI) represents an island of Lake Bomieville standing on the desert near what is known as the "Old River Bed." The nucleus of solid rf)ck was in this instance nearly demolished before the work of the waves was aiTested by the lowering of the water. The Wave-built Terrace-It lias alrcadv becu poiutcd out that when a separa- tion of the littoral current from the coast line is brought about by a diverg- ence of the current rather than of the coast line, there are two cases, in the 'Notes on the Daveuport gravel drift. Cuiiatliau Journal, New Series, vol. C, 1861, pp. 247-253. 56 LAKE BONNEVILLE. first of which the current continues at the surface, while in the second it dives beneath the surface. It is now necessary to make a further distinc- tion. The current dejjarting from the shore, but remaining at the surface, . may continue with its original velocity or it may assume a greater cross- section and a diminished velocity. In the first case the shore drift is built into a spit or other linear embankment. In the second case it is built into a terrace. The quantity of shore dnft moved depends on the magnitude of the waves; but the speed of transit depends on the velocity of the current, and wherever tliat velocity diminishes, the accession of shore drift must exceed the tran.smission, causing accumulation to take place. This accumu- lation occurs, not at the end of the beach, but on its face, carrying its entire profile lakeward and producing by the expansion of its crest a tract of new- made land. If afterward the water disappears, as in the case of an extinct lake, the new-made land has the character of a terrace. A current which leaves the shore by descending, practically produces at the shore a diminu- tion of flow, and the resulting embankment is nearly identical with that of a slackening superficial current. The waA'e-built terrace is distinct from the wave-cut terrace in that it is a work of constraction, being composed entirely of shore th'ift, Mliile the wave-cut terrace is the result of excavation, and consists of the pre-existent terrane of the locality. The wave-built terrace is an advancing embank- ment, and its internal structure is characterized by a lakeward dip (Fig. 13). It is thus contrasted with the retreating embankment (Fig. 12). Fig. 12. — Stctiouof a Lioear Enibaukm^nt retreating landward. Tliedolti-d line bhows tbt- original pusitioo of tbe crest. ''v^k*Al/fi^i^/'tiiy4'^/'i/.i^v*'-.^'^:'X^^^^^ Fio. 13.— Section of a ■Wave-bnilt Terrace. The surface of the wave-built terrace, considered as a whole, is level, but in detail it is uneven, consisting of parallel ridges, usually curved. Each WAVE-BUILT TERRACES. 57 of these is referable to some exce}Dtional Siorm, the waves of which threw the shore di-ift to an unusual height. TMiere the shore drift consists wholly or in large part of sand, and the prevailing winds are toward the shore, the wave-built terrace gives origin to dunes, which are apt to mask its normal ribbed structure. The locality most favorable for the formation of a wave-built terrace is the head of a triangular bay, up whioh the waves from a large body of water are rolled without obstruction. The wind sweeping up such a bav cariies the surface of the water before it, and the only return cun-eut is au undertow originating near the head of the bay. The superficial advance of the water constitutes on each shore a httoral current conve}"ing shore drift toward the head of the bav, and as these littoral cuiTents are diminished and finally entirely dissipated by absorption in the undertow, the shore drift taken up along the sides of the bay is deposited. If the head of the bay is acute, the first embankment built is a curved bar tangent to the sides and- con- cave toward the open water. To the face of this successive additions are made, and a terrace is gradually produced, the component ridges of which are approximately parallel. The sharpest curvature is usually at the ex- treme head of the bay. The converging currents of such a bay give rise to an undertow which is of exceptional velocity, so that it trans2:)0rts with it not only the finest detritus but also coarser matter, such as elsewhere is usually retained in the zone of Avave action. In eftect there is a resorting of the material. The shore drift that has traveled along the sides of the bay toward its head, is diA-ided into two portions, the finer of which passes out with the reinforced undertow, while the coarser onlv is built into the terrace. The v-Terrace and v-Bar.-It rcmaius to describo a t}"pe of tciTacc for which no satisfactory explanation has been 'reached. The shores of the ancient Pleis- tocene lakes afi'ord numerous examples, but those of recent lakes are nearly devoid of them, and the writer has never had opportunity to examine one in process of formation. They are triangular in ground plan, and would claim the title of delta were it not appropriated, for they simulate the Greek letter more strikingly than do the river-mouth structures. They are built against coasts of even outline, and usually, but not always, upon slight 58 LAKE BONNEVILLE. salients, and they occur most frequently in the long, narrow^iarms of old lakes. One side of the triangle rests against the land and the opposite angle points toward the open water. The free sides meet the land with short ^ curves of adjustment, and appear otherwise to be normally straight, although they exhibit convex, concave, and sigmoid flexures. The growth is by ad- ditions to one or both of the free sides; and the nucleus ap]iears always to lun-e been a miniature triangular terrace, closely resembling the final struct- ure in shajje. In the Bonne^'ille examples the lakeward slope of the terrace is usually very steep down to the line where it joins the ])reexisteut slope of the bottom. There seems no reason to doubt that these embankments, like tlie others, were built by currents and waves, and such being the case the for- matiA'e currents must have diverged from the shore at one or both the land- Avard angles of the terrace, but the condition detenuining this divergence does not a})pear. In some cases the two margins appear to have been determined by cur- rents ;i])j)roacliing the terrace (doubtless at diiferent times) from opposite directions; and then the terrace margins are concave outward, and their continence is prolonged in a more or less irregular point. In most cases, however, the shore di-ift appears to have been carried by one current from the mainland along one m.argin of die teiTace to the apex, and by another cm-rent along the remaining side of the terrace back to the mainland. The contours ai-e then either straight or convex. In Lake Bonneville it happened that after the best defined of these ter- races had attained nearlv their final width the lake increased in size, so that they were hnmersed beneath a few feet of water. While the lake stood at the higher level, additions were made to the terraces b}' the building of lin- ear embankments at their outer margins. These were carried to the water surface, and a triangular lagoon was imprisoned at each locality. The sites of these lagoons are now represented by flat triangular basins, each walled in by a bar bent in the foi-m of a V. These bars were at first observed without a clear conception of the terrace on which they were founded, and the name V-har was applied. The V-bai-, while a conspicuous feature of V S.GPG;,0Or-AL SUPVEV h/-J.Z BJKfTEMLLE PL\11 I'l.Ais oi" i.()()i'i-;i) AND v-siiAi'i:i) i:mi;ankmi:xis, ()i;si:i{\i;i» on TlIK SIIOIIKS OK \AK\: l!()NNK VIlJ.i:. %i'K -, i' i. k, ■ -i ■iJit'ai-Bv ^•«S*SS( i^r s4al«iWiSr FFET V i^' Wi .r^^« fmi 1, .M/// Miit.-ih , -siiiii., I'.ilhi '1. II Husl B. i't'iill III' Ihf Mi'iiirttnit \n ^'"^40^ .Vofr The tirroi\'.*i .show 1 tJu\ ff/rerOftti i/t ivhirh \ **^*„ Vl(%W.»„„„„„„,„^,,,«m«»««" '"'■»»>* vs^Uiiimuiiiiiiiuutt' 7 II v;^/^ 1,1 OI, I Hivrr Hi'il U',12 /'r,ii-\-s I'dtlfv, ruoi U',,-n,, Sj,riiiif 111 .r»<(/' sii„i.i,,ii ]tr>iMii )iv ti T)i->iu|>i>(>ii TRIANGULAR TERRACES. 59 the Boune^■ille shores, is not believed to be a normal feature of lakes raain- tainiuiJ- a constant level. o DRIFTING SiND; DTTNES. The dune is not an essential shore feature, but is an accessory of fre- quent occiuTence. Dunes are formed wherever the wind drifts sand across the land. The conditions essential to their production are wind, a supply of sand, and sterility or the absence of a protective vegetal growth. In arid regions sterility is affttrded by the climatic conditions, and the sand furnislied by river bars laid bare at low water, and by the disintegration of sand rocks, is taken up by the wind and built into dunes; but where rain is abundant, accumulations of suc-h sort are protected by vegetation, and the only sources of supply are shores, either modern or ancient. Shore drift nearly always contains some sand, and is frequently com- posed exclusively thereof The undertow carries off tlie clay, which might otherwise hold the sand particles together and prevent their removal by the wind; and pebbles and bowlders, which, by their superior weight oppose wind action, are less able to withstand the attrition of littoral transportation, and disappear by disintegration from any train of shore drift which travels a considerable distance. Iilinbankraents are therefore apt to be composed largely of sand; and the crests of embankments, being exposed to the air during the intervals between gi*eat storms, yield dry sand to the gentler winds. The sand drifted from the crests of free embankments, such as barriers, spits, and bars, quickly reaches the water on one side or the other. What is blown to the lakeward side falls within the zone of wave action, and is affain worked over as .shore drift. Wliat is blown to the landward side ex- tends the area of the embankment, correspondingly encroaching on the lagoon or bay. Sand Ijlown from the crests of embankments resting against the land, such as beaches and terraces, will spread over the land if the prevailing wind is favorable. In cases where the prevailing wind is toward the lake the general movement of sand is, of course, in that direction, and it is merely 60' LAKE BONNEVILLE. returned to the zone of the waves and readded to the shore drift; but where the prevaiUng winds are toward the land, dunes are formed and skiwly rolled forward by tlie wind. The sui)ply of diy sand aflbrded by beaches is com- paratively small, and dunes of magnitude are not often formed from it. The great sand magazines are wave-built terraces, and it is from these that the trains of sand so formidable to agriculture have originated. The sands accumulated on the shores of lakes and oceans now extinct are sometimes so clean that vegetation acquires no foothold, and the wind still holds dominion. The "oak openings" of Western States are usually of this nature; and in the Great Basin there are numerous trains of dunes convejaug merely the sand accumulated on the shores of the Pleistocene lakes. One product of littoral deposition — the delta — remains undescribed; but this is so distinct from tlie embankment, not only in fonn but in process of construction, that its consideration will be deferred until the interrelations of the tlii-ee processes already described have been discussed. THE DISTRIBUTION OF WATE-WROUOnT SHORE FEATURES. Upon every coast there are certain tracts undergoing erosion; certain others receive the products of erosion, and the intervals are occui)ied by the structures peculiar to transportation. Let us now inquu-e what are the con- ditions determining these three phases of shore shaping. It will be convenient to consider first the conditions of transportation. In order that a particular poi-tion of shore shall be the scene of littoral trans- portation, it is essential, first, that there be a supply of shore di-ift; second, that there be shore action by waves and currents; and in order that the local process be transportation simply, and involve neither erosion nor depo- sition, a certain equilibrium must exist between the quantity of the shore di-ift on the one hand and the power of the waves and currents on the other. On the whole this equilibrium is a delicate one, but within certain narrow limits it is stable. That is to say, there are certain slight variations of the indi\'idual conditions of equilibrium, which disturb the equilibrium only in a manner tending to its immediate readjustment. For example, if the shore DISTRIBUTION OF EHOSION AND DEPOSITION. 61 di-ift receives locally a small increment from stream drift, this increment, by adding to the shore contour, encroaches on the margin of the littoral cuirent and produces a local acceleration, which acceleration leads to the removal of the obsti-uction. Similarly, if from some temporary cause there is a local defect of shore drift, the resulting indentation of the shore contour slackens the littoral current and causes deposition, whereby the equili])rium is restored. Or if the force of the waves is broken at some point by a temporary obstruc- tion outside the line of breakers, as for example by a wreck, the local dimi- nution of wave agitation produces an accumulation of shore drift whereby the littoral current is naiTowed and thus accelerated until an adjustment is reached. Outside the limits thus indicated everything which disturbs the adjust- ment between quantity of shore di'ift and capacity of shore agents leads either to jDrogressive local erosion or else to progressive local depo.sition. The stretches of coast which eitlier lose or gain ground are decidedly in excess of those which merely hold their OAvn. An excessive supply of shore drift over and above what the associated cun-ent and waves are competent to transport leads to deposition. This occurs where a stream of some magnitude adds its quota of debris. A mod- erate excess of this nature is disposed of by the formation of a wave-built terrace on the lee side of the mouth of the stream, that is, on the side toward Avhich fluws the littoral current accompanying the greatest waves. A great excess leads to the formation of a delta, in which the stream itself is the con- structing affent and the influence of waves is subordinate. On the other hand, there is a constant loss of shore di-ift by attrition, the particles in transit being gradually reduced in size luitil they are removed from the httoral zone, by the undertow. As a result of the defect thus occa- sioned, a part of the energy of the waves is expended on the subjacent terrane, and the work of transportation is locally accompanied by a sufficient amount of erosion to replenish the wasting shore drift. For the maintenance of a continuous beach in a pennanent position, it appears to be necessary that small streams shall contribute enough debris to compensate for the waste by attrition. / 62 - LAKE BONNEVILLE. Theoretically, transportation must be exchanged for erosion wherever there is a local increase in the magnitude of waves, and for deposition where there is a local decrease of waves; but practically the proportions of waves are so closely associated with the velocities of the accompanying cun-ents that their eft'ects have not been distinguished. The factor which most frequently, by its variation, disturbs the equi- librium of shore action is the littoral cun'ent. It has already been pointed out that whereA^er it leaves the shore, shore drift is deposited; and it is ef|ually true that ■\\'herever it comes into existence by the impinging of an (jpen-water current on the shore, shore di'ift i.s taken up and the ten-ane is eroded. It has been shown also that the retardation of the littoral current produces deposition, and it is equally true that its acceleration causes ero- sion. Every variation, therefore, in the direction or velocity of the current at the shore has a definite effect in the determination of the local shore process. Reentrant angles of the coast are always, and reentrant curves are usually, places of deposition. The reason for tliis is twofold: first, cuiTCuts which follow the shore move with diminished velocity in passing reentrants ; second, currents directed toward the shore escape from reentrants only by undertow, and, as heretofore explained, build terraces at the heads of the embayments. Salient angles are usually eroded, and salient curves nearly always, the reasons being, first, that a current following the shore is relatively swift opposite a salient, and, second, that a current directed toward the shore is apt to be divided by a salient, its halves being converted into littoral cur- rents transporting shore drift in ojjposite directions away from the salient. Some salient angles, on the contrary, grow by deposition. This occurs where the most important current approaches by following the shore and is thrown off to deep water by a sahent. The most notable instances are found on the sides of narrow lakes or arms of lakes, in which case currents approach- ing from the direction of the length are accompanied by greater waves than those blown from the direction of the opposite shore, and therefore dominate in the determination of the local action. SIMPLIFICATION OF COAST LLN'ES. 63 It thus appears that there is a general tendency to the erosion of saHents and the filHng of emba vments, or to the simphfication of coast outlines. Tliis tendency is illustrated not only hy the shores of all lakes, but by the coasts of all oceans. In the latter case it is slightly diminished by the action of tide^, which occasion cuiTents tending to keep open the mouths of estuaries, but it is nevertheless the prevailing tendency. The idea which sometimes aji- pears in popular writings that embaA-ments of the coast are eaten out by the ocean is a sm'vival of the antiquated theory that the sculpture of the land is a result of "marine denudation." It is now understood that the diver- sities of land topography are wrought by stream erosion. Figure 8, rejiresenting about seven miles of the shore of Lake Ontario, illustrates the tendency toward simplification. Each bluff" of the shore marks the truncation by the waves of a cape that was originally more salient. Each beach records the partial filling of an original bay. Each bar is a wave- built structure partitioning a deep reentrant from the open lake. The la- goons receive the detritus from the streams of the land and are filling ; partly for this reason there is a local defect of shore di-ift, and the coast is receding by erosion; and by this double process the original reentrants are suffering complete effacemeut. For the original coast line — a sinuous contour on a surface modeled by glacial and fluvial agencies — will be substituted a rela- tively short line of simple curvature. The simi)lification of a coast line is a work invoU'ing tune, and the amount of work accomplished on a particular coast affords a relative meas- ure of tlie time consumed. There are many modif^-ing conditions — the fetch of waves, the off'-shore dejjth, the material of the land, the original configuration, etc. — and these leave no hope of an absolute measure; but it is possible to distinguish the 3'oung coast from the mature. AVhen a water level is newly established against land -n-ith sinuous contour, the first work of the waves is the production of the beach profile. On the gentlest slopes they do this by excavating the teirane at the point where they first break and throwing the material shoreward so as to build a barrier. On all other slopes they establish the profile by car\ang a terrace with its correla- tive cliff. The coarser products of ten'ace-cuttiug gather at the outer edge 64 LAKE BONNEVILLE. of the terrace, helping to increase its breadth; the finer fall in deeper water and help to equalize the off-shore depth. The terrace gradually increases by the double pi'ocess of cutting and filling until it has attained a certain minimum width essential to the transportation of shore di-ift. This Avidth is for each locality a function of the size of the gi-eatest waves. Before it is reached, the fragments detached from the cliff linger but a short time on the face of the ten-ace; after a few excursions u\) and down the slope they come to rest at the edge of the deeper water. When it is reached — when the beach profile is complete — the excavated fragments torn from the cliff no longer escape from the zone of wave action, but are rolled to and fro by the waves of every storm, lose their angles by attrition, and are drifted along by the shore cun-ent. It may happen that the material of the cliff is a gravel, already rounded by some earlier and independent process, but when this is not the case, the cut-terraces of adolescent and mature coasts are distinguished by the angular forms on the one hand and the rounded forms on the other of the associated detritus. When the fonnation of shore drift has once been begun, its further development and the development of effi- cient shore currents are gi-adual and by reciprocation. The spanning of minor recesses of the coast-line by its beach helps to smooth the way for the shore current, and the current promotes the beach. Embankments come later, when ways have been straightened for the current and shore drift, and those first constructed usually attempt the partition of only small em- bajTnents. The more extended and powerful shore currents, competent to span the bays between the greater headlands, become possible only after minor rugosities of coast and bottom have disappeared. Low but nearly continuous sea-cliffs mark the adolescent coast; simple contours and a cordon of sand, interspersed with high cliffs, mark the matui-e coast. As a result of the inconstancy of the relations of land and water, it is probable that all coasts fall under these heads, but Richthofen has sketched the features of the theoretic senile coa.st.^ As sea-cliffs retreat and terraces gi-OAv broader the energy of the waves is distributed over a wider zone and its erosive Avork is diminished. The resulting defect of shore drift permits t . ^.^ * Fuhrer fiir ForBchangsreisende, p. 338. ADOLESCENT, MATDRE AND SENILE COASTS. 65 the erosion of embankments, and the withdrawal of their protection extends the hne of chff; but eventually the whole line is driven back to its limit and erosion ceases. The cliffs, no longer sapped by the waves, yield to atmospheric agencies and blend with the general topograpliy of the land. Shore drift is still supplied by the streams and is spread over the broad lit- toral shoal, where it lies until so comminuted by the waves that it can float away. The length of the period of adolescence varies with local conditions. Where the waves are jiowerful, maturity comes jsooner than wliere they are weak. It comes sooner, too, where the material to be moved by the waves is soft or incoherent than' where it is hard and firm; and it comes early where the submerged contours and the contour at the water's edge have few in-egularities. Different parts of the same coast accordingly illustrate different stages of development. The shores of Lake Bonneville are in general mature, but in small sheltered bays they are adolescent. The shore of Lake Ontario is in general mature, being traced on a surface of glacial drift, but near the outlet is a region of bare, hard rock disposed in promontories and islands, and there much of the coast is adolescent. The classic "parallel roads" of Glen Roy in Scotland illustrate the ado- lt?Sceut tvpe, and this although the local conditions favor rapid development. The smooth contom-s of the valley gave no obstruction to shore cunents, dejitli and length of lake jiermitted the raising of large waves, and a mantle of glacial drift afforded matenal for shore drift; but the beach profile was not completed, the bowlders of the nan-ow ten-aces are still subangular, and there are no embankments. It is fairly inferred that the time repre- sented by each shore-line was short.. STREAM WORK ; THE DELTA. The detritus brought to lakes by small streams is overwhelmed by shore di-ift and merges with it. The tribute of large streams, on the contrary, overwhelms the shore diift and accimiulates in deltas. In the formation of a normal delta the stream is the active agent, the lake is the passive recipient, and waves play no essential part. MON I 5 QQ LAKE BONNEVILLE. The process of delta formation depends almost wholly on the following law : The capaciti/ and competence of a stream fur tlm transportation of detritus arc increased and diminished hij the imrcasc and diminution of the vehrifij. 1 he capacity of a stream is measured by the total load of debris of a given fine- ness which it can cany. Its competence is measured by the maximiuu size of the particles, it can move. A swift current is able to trans])Oi-t both more matter and coarser matter than a slow cuiTont. The competence depends on the velocity of the water at the bottom of the channel, for the largest particles the stream can move are merely rolled along the bottom. Finer })articles are lilted from the bottom by threads of current tending more or less u])ward, and before they sink again are carried forward by the general flow. Their suspension is initiated by the bottom current, Ijut tlie length and speed of their excursion depend on the general velocity of the cun-ent. Capacity is therefore a function of the velocity of the more superficial threads of current as well as of those which follow the bottom. Suppose that a river freighted with the Avaste of the land is newly made tributary to a lake. Its water flows to the shore, and shoots out thence over' the relatively still lake water until its momentum has been communi- cated by friction to so large a body of water as to practically dissipate its velocity. From the shore outward the velocity at the bottom is the velocity of the lake water and not that of the ri^-er water, and is inconsiderable. The entire load consequently sinks to a final resting place and becomes a deposit. The coarse particles go down in iimuediate contiguity to the shore. The finest are carried far out before they escape from the superficial stratum of river water. The sinking of the coarse material at the shore has the effect of build- ing out a jilatform at the level of the bottom of the river channel. Postulate the construction of this platform for some distance from the shore without any modification of the longitudinal profile of the river, the river surface descending to the shore and then becoming horizontal. EAidently, the hor- izontal portion has no energy of descent to propel it, and yet is opposed by friction ; its velocity is, therefore, retarded, its capacity and competence are ' It 18 said that some glacier-fed streams on entering lakes pass under instead of over the lake water and that peculiar delta features result, but these are not fully described. DELTA BUILDING, ' 67 consequently^ diminished, and it drops some of its load. The fall of detritus builds up the bottom at the point Avhere it takes place, and causes a check- ing of the current inmiediately above (up stream). This in turn causes a deposit; and a reciprocation of retardation and deposition continues until the profile of the stream has acquired a continuous grade from its mouth at the extremity of the new platform backward to some stee2:)er part of its channel — a continuous grade sufficient to give it a velocity adequate to its load. The jxistulate is, of course, ideal. The river does not in fact build a level bed and afterward change it to a slope, but carries forward the whole work at once, maintaiiiing continuously an adjustment between its grade and its work. Moreover, since the dejjosition begins at some distance from the mouth, the lessening load does not require a uniform grade and does not produce it. The gi-ade diminishes gradually lakeward to the foot of the deposit slope, so that the longitudinal profile is slightly concave upward. At the head of the deposit slope there is often an abrupt change of grade. At its foot, where the maximmn deposit is made, there is an abrupt change of a double character; the incline of the river surface is exchanged for the horizontal plane of the lake surface; the incline of the river bottom is ex- changed for the steeper incline of the delta front. The river cuiTent is swifter in the middle than at the sides, and on a deposit slope, where velocity is nicely adjusted to load, the slight retarda- tion at the sides leads to deposition of suspended matter. A bank is thus produced at either hand, so that tlie water flows down an elevated sluice of its own constraction. The sides are built up pari passu with the bottom, but inasmuch as they can be increased only by ovei-flow, they never quite reach the flood level of the water surface. A river thus contained, and a river channel thus constructed, constitute an unstable combination. So long as the bank approximates closely to the level of the surface at flood stage, the cuiTent across the bank is slower than the cun-ent of the stream, and deposits silt instead of excavating; but whenever an accidental cause so far lowers the bank at some point that the current across it during flood no longer makes a deposit, there begins an erosion of the bank which increases rapidly as the volume of escaping water is auginented. A side channel is thus produced, which eventually becomes deeper than the 68 LAKE BONNEVILLE. main or original channel and draws in the greater part or perliajis all of the water. The ability of the new channel to drain the old one dej)ends on two thing.s: fir.st, the outer slope of the bank, from the circum.«itances of its con- struction, is sloojicr than the de.scent of the bottom of the chamt'l; second, the first-made channel, although originally following the shortest route to the lake, has so far increased its length by the extension of its mouth that the water escaping over its bank may find a shorter route. The river channel is thus shifted, and its mouth is transferred to a new ])oint on the lake shore. Repetititin of this j)rocess transfers the work of alluvial deposition from place to j)lace, and causes the river to build a sloping jdain instead of a simple dike. The lower edge of the j)lain is everywhere equidistant liom the head of the deposit slope, and has therefore the form of a circular arc. The inclination is in all directions the same, varying only with the dimin- ishing grade of tlie deposit slojic, and the fomi of the plain is thus approxi- luiitelv conic. It is, in fact, identical with the product of land-shajjing known as the alluvial cone or alluvial fan. The symmetry of the ideal form is never attained in fact, because the process of shifting imjjlies inequality of surface, but the approximation is close in cases Avhere the grade of the de})osit slope is high, or where the area of the delta is large as compared with the size of the channel. Fig. 14.— Section of a Delta. At the lake shore the manner of deposition is different. The heaxaer and coarser part of the river's detrital load, that which it pushes and rolls along the bottom instead of caning by suspension, is emptied into the lake and slides down the face of the delta with no impulse but that given by its own weight. The slope of the delta face is the angle of repose of this coarse material, subject to such modification as may result from agitation by waves. DELTA STRUCTURE. 69 The finer part of the detritus, that which is transported by suspension, is carried beyond the deUa face, and .sinks more or less sk)wly to the bottom. Its distdljutiou depends on its rehative fineness, the extremely fine material being widely diffused, and the coarser falling near tlie foot of the delta face. The depth of the deposit formed from suspended material is greatest near the delta and diminishes gradually outward, so that the .slope of the delta face merges by a cui-A-e with the slope of the bottom beyond. As the delta is built lakeward, the steeply inclined layers of the delta face are superposed over the more level strata of the lake bottom, and in tuni come to support the gently inclined layers of the delta plain, so that any vertical section of a normal delta exhibits at the top a zone of coarse material, bedded with a gentle lakeward inclination, then a zone of similar coar.se material, the laminations of which incline at a high angle, and at bottom a zone of fine material, the laminations of which are gently inclined and unite by curves with those of the middle zone. The characters of the fossil delta, or the delta as it exists after the des- iccation of the lake concerned in its formation, are as follows: The upper surface is a terrace Avith the form of an alluvial fan. Tlie lower slope or face is steep, ranging from 10° to 25°; it jijins the upper slope b}- an angle and the plain below by a curve. The line separating tlie upper surface from the outer slope or face is horizontal, and, in connnon with all other horizon- tal contours of the structure, is approximately a circular arc. The upper or landward limit of the upper surface is a line horizontally uneven, depend- ing on the contoi:rs of the antecedent topograpln' Tlie lower limit of the face is a vertically inieven line, dejiending on tlie antecedent topograph v as modified by lake sediments. The material is detrital and well rounded; it exhibits well-marked lines of deposition, rarely taking the character of bed- ding. The structure as seen in section is tripartite (Fig. 1.")). In the upper division the lines of deposition are parallel to the upper surface of the delta ; in the middle division they are parallel to the steep outer face, and in the lower division they are gently inclined. The separation of the middle divis- ion from the lower is obscure. Its separation from the upper is definite and constitutes a horizontal plane. The fossil delta is invariably divided into two parts by a channel running from its apex to some jiart of its periphery 70 LAKE BONNEVILLE. and occupied l)y a stream, the agent of its constmction becoming, under changed conditions of base level, the agent of demolition. The fan-like outline of the nonnal delta is modified wherever wave ac- tion has an importance comparable with that of stream action. Among the great variety of fonns resulting from the combination of the two agencies, there is one which re^ieats itself with .suf- ficient frequency to deserve special men- ^^^^ tion. It occurs where the force of tlu^ <-i^^^^c^?^5^^^^0^5^^l«^^ waves is considerable and the amount gJ^iij^^i'^r^^^^ii^^l^^^Kll^^^^ oi' shore drift brought by them to the l^i^i^ S'^^-^^^^^^^^^^sl®^^^ delta is inconsiderable. In such case ^-.^ ' . wiiv:;;Tfjr;^ ^1^^ shore current from either direction is deflected by the mass of the delta, and wave action adjusts the contour of the delta to conformity with the deflected shore current. If the wave influences from opposite directions are equal, the delta takes the fonn of a symmetric tri- angle similar to that of the V-terrace. Numerous illustrations are to be seen on the shores of Seneca and CajTiga Lakes, where the conditions are peculiarly favorable. The lake is long and narrow, so that all the efficient Avave action is associated Avith strong shore currents, and these alternate in direction. The predominant rock of the sides is a soft shale, so easily triturated by the waves that the entire product of its ero.sion escapes with the undertow, and no shore drift remains. The sides are straight, and each tributary stream builds out a little promon- tory at its mouth, to which the waves give form. Some of these triangular deltas eml)ody perfectly the Greek letter, but they turn the apex toward the water instead of toward the land. Fig. 15. — Vertical eection iu a Delta, sliowiug Ibe l^pi cal auccession of strata. THE WALLING IN OF "WALLED" LAKES. 71 ICE WORK ; THE RAMPART. This feature does not belong to lakes in general, but is of local and exceptional occun-ence. It was named the "Lake Rampart" by Hitchcock, wlio gave the first satisfactory account of its origin.^ Earlier observations, containing the genn of the explanation of the phenomenon, were made by Lee^ and Adams.' A later and indepen- dent explanation was given by Wliite.* «■,■/■■■■„ In ignorance of Hitchcock's description, fe||i,=;,,.,^^;;:iS^^^^= 1 grave credit m the r nth Annual neport oi ^ o , *=> >■ Fig. 16.— Section of aKampart. the U. S. Geological Survey to White, and myself proposed the name "Shore "Wall." I now substitute Hitchcock's name, "Rampart", being moved thereto not oidy by the priority and the ejninent fitness of the name, but by the consideration that "Shore Wall" is liable to be confounded with "Sea Wall", a term applied on some marine coasts to steeji-faced embankments of shingle. Tlie ice on the surface of a lake expands \<\\Aq, forming, so as to crowd its edge against the .shore. A further h)wering of temperature produces contraction, and this ordinarily results in the ojiening of vertical fissures. Tliese admit tlic water from below, and by the freezing of that water tliey art' filled, so that when exj)ansion follows a subsequent rise of temperature the ice cannot assume its original position. It consequenth' increases its t( >t;d area and exerts a second thrust upon the shore. Wliere tlie shore is abrupt, tile ice itself vields, either by cru.shing at the margin or bv the formation of aiiticliiials elsewhere; but if the shore is generally shelving, the margin of the ice is forced up the acclivity, and carries Avitli it any bowlders or other loose material about which it may have frozen. A second lowering of tem- perature does not withdraw the protruded ice margin, Imt initiates ftther cracks jiiid leads to a repetition of the shoreward thrust. The ])rocess is repeated from time to time during the winter, but ceases with the melting of ' Lake RaiupartH in Veriuoiit. By Cfaas. H. Hitchcock. In Proc. Am. Asa. Adv. Sci., vol. 13, 18G0, p. 335. »C. A. Lee. Am. .lour. Sci., vol. 5, lS->2, pp. 34-37, and vol. 9, 1825, pp. 239-241. ^J. Adauis. Am. Jour. Sci., vol.9, Icfti^), pp. l.JO-144. { mountain ranges, appearing generally at their bases, just where the solid rock of the mountain mass is adjoined by the detrital foot slope. The)' occasionally encroach upon the latter, and it is in such case that they are most conspicuous as well as most likely to be mistaken for sea-cliffs. Although in following the mountain bases they do not vary greatly in altitude, yet they never descri])e exact contours, but ascend and descend the slopes of the foot hills. Tlie cre.st of such a cliff is usually closely parallel to the base for long distances, but this parallelism is not absolute. The two lines graduallv converge at either end of the displace- ment. In exceptional instances they converge rapidly, giving the cliff a somewhat abrupt termination, and in such case a new cliff appears en Echelon, COMPARISON OF CLIFFS. 77 coTitiiming' the displacement with a shght offset. In Chapter VIII these cHtis aw described at length and illustrated. by \'ie\vs and diagraras. The Land-Slip ciiff.-Tlie laud-slip diifers from the fault chiefly in the fact that it is a purely superficial phenomenon, having its Avhole history upon a visible external slope. It occui-s usually in unconsolidated material, masses of which break loose and move downward short distances. The cliffs pro- duced by their separation from the general or pai-ent mass, are never of great horizontal extent, and have no coromou element of fonn except that they are concave outward. They frequently occur in groups, and are apt to con- tain at their bases little basins due to the backward canting which forms part of the motion of the sliding mass. comparison.-The sea-cHff differs from all others, first, in that its base is horizontal, and, second, in that there is associated with it at one end or other a beach, a barrier, or an embankment. A third ^•aluable diagnostic feature is its uniform association with the terrace at its base; but in this respect it is not unique, for the clifl" of differential degradation often springs from a ten-ace. Often, too, the latter is nearly horizontal at base, and in such case the readiest comparative test is found in the fact that the sea-cliff is inde- pendent of the texture and structure of the rocks from which it is carved, while the other is closely dependent thereon. The sea-cliff is distinguished from the stream-cliff by the fact that it faces an open Aalley broad enough and deep enough to permit the genera- tion of efficient waves if occupied by a lake. It is distinguished from the coulee edge by its independence of rock structure and by its associated ter- race. It differs from the fault scarp in all those peculiarities which result from the attitude of its antecedent ; the water surface concerned in the for- mation of the sea-cliff is a horizontal plane; the fissure concerned in the fonnation of the fault scarp is a less regular but essentially vertical j)lane. The former crosses the inequalities of the preexistent topography as a con- tour, the latter as a traverse line. The land-slip cliff is distinguished by the marked concavity of its face in horizontal contour. The sea-cliff is itsually convex, or, if concave, its contours are long and sweeping. The fonner is distinguished also by its discontinuity. 78 LAKE BONNEVILLE. TERRACES. A terrace is a horizontal or nearly horizontal topographic facet inter- rupting a steeper slope. It is a limited ])lain, from one edge of which the ground rises more or less steeply, while from the opj)Osite edge it descends more or less steeply. It is the "tread'' of a topograjihic step. Among the features peculiar to shores are three terraces: the wave-cut, the wave-built, and the delta. These will he com2:)ared with the tei-race by differential degi-adation, the stream terrace, the moraine ten-ace, the fault terrace, and the land-slip teiTace. The Terrace by Differential Degradation—The Same general -CirCUmStanCeS of rOck texture which under erosion give rise to clifts ])roduce also terraces, but the terraces are of less frequent occurrence. The only case in wnich they are at all abundant, and the only case in which they need be discriminated from littoral teiTaces, is that in which a system of strata, heterogeneous in texture and l^'ing nearly horizontal, is tinincated, either by a fault or by some erosive action, and is afterwards subjected on the trancated section to atmospheric waste. The alternation of hard and soft strata gives rise under such cir- cumstances to a series of alternating cliffs and terraces, the outcrop of each hard stratmn appearing in a more or less vertical cliff, and the outcrop of each soft stratum ]>eing represented by a gently sloping teirace, united to the cliff above by a curve, and, in tj^jical examj)les, separated from the cliff below by an angle. The length of such terraces in the direction of the strike is usually great as compared with their width from cliff to clifi'. They are never level in cross profile, but (1) rise wth gradually increasing sloj^'from the crest of one cliff to the l)ase of the next, or (2) descend from the crest of one cliff 'to a medial dejiression, and thence rise with gradually increasing si ojie to the base of the next. The first case arises whei-e the ten-ace is narrow or the dip of the strata is toward the lOAver cliff, the second case where the terrace is broad and the dip of the rocks is toward the upper cliff. In the first case the di-ainage is outward to the edge of the lower cliff; in the second it is toward the medial depression, whence it escapes by ihe narrow channels carved through the rock of the lower cliff. DEGRADATION TERRACES. 79 The Stream Terrace.-Tlic coiulitioii of rajiiil Grosioii ill ally regioii is uplift. In a tract wliich lias recently been elevated, the rate of degradation is unequal, the waste of the water channels heiiig more rapid than that of the surface in general, so that they are deeply incised. Eventuall}', however, the corrasion of the water channels so reduces their declivities that the velocities of cuirent suffice merely for the transportation outward of the detritus disengaged by the general waste ot surface. In other words, a base level is reached. Then the process of lateral corrasion, always carried on to a certain extent, as- sumes prominence, and its results are rendered conspicuous. Each stream wears its banks, swinging from side to side in its valley, always cutting at one side, and at the other building a shallow deposit of alluvium, which con- stitutes its flood j)laiii. The valley, having before consisted of the river channel margined on either side by a cliff, now consists of a plain bounded at the sides by cliff's and traversed by the river channel. If now the corrasion of the stream bed is accelerated by a new uplift or other cause, a smaller valley is excavated within the first and at a lower level. So much of the original flood plain as remains constitutes terraces flanking the sides of the new valley. Outwardly one of these terraces is bounded by the base of the old line of cliffs, which may by decay have lost their vertical habit. Inwardly it is bounded by the crest of the new line of cliffs produced by lateral corrasion. Acceleration of doAvnward corrasion is brought about in many ways. As already mentioned, it may be produced by a new uplift, and this stimu- lus is perhaps the most potent of all. It is sometimes ])roduced by the downtlu'ow of the tract to ^^•hich the streams discharge, or, what is nearly the same thing, by the degradation of stream cliaunels in that tract. It is also brought about, within a certain range of conditions, by increase of rainfall; and finally, it always ensues sooner or later from the defect of transported material. The general waste of the onginally uplifted tract undergoes, after a long period, a diminution in rapidity. The streams have therefore less detritus to transport. Their channels are less clogged, and they are enabled to lower them by corrasion. Perhaps it would be better to say that after the immediate consequences of uplift have so far passed away that an equilibiium of erosive action is established, the^ degradation of 80 LAKE BONNEVILLE. the entire tract proceeds at a slow continuous rate, the slight variations of which are in a sense accidental. Lateral corrasion under such circumstances coexists in all stream channels with downward corrasion, and is the rdore important process; but the horizon of its action is continuously lowered by the downward corrasion. The terraces which result represent only the stages of a continuous process. In a great number of stream valleys, not one but many ancient flood j)lain.s find record in terraces, so that the stream terrace is a familiar topo- graphic feature. ^Yhcn a stream meandering in a flood plain cDcroaches on a wall of the valley and corrades laterally, it cames its work of excavation down to tlie level of the bottom of its channel; and afterward, when its course is shifted to some other part of the valley, it leaves a deposit of alluvimn, the ujjper surface of wliich is barely submerged at the flood stage of the stream. The depth of alluAdum on the flood plain is therefore measured by the ex- treme depth of the current at high water It constitutes a practically even sheet, re.sting on the undisturbed teirane beneath. WTien the stream finally abandons it, and by carving a deeiDcr channel, converts it into a terrace, the terrace is necessarily bipartite. Above, it consists of an even layer of allu- vial matenal, fine at top and coarse at bottom; below, it consists of the preexistent formation, whatever that may be. ^Vliere the lower portion is so constituted as to resist erosion, it loses after a long period its alluvial blanket, and then the teiTace consists simply of the floor of hard rock as pared away by the meandering stream. The coarse basal portion of the alluvium is the last to disappear; and if it contains hard bowlders some "of these will survive as long as the form of the teiTace is recognizable. The elder Hitchcock enumerated and described four types of stream terrace: the lateral teiTace, the delta ten-ace (grouped by the writer witli shore ten-aces), the gorge teirace, and the glacis terrace;' and Miller, whose clear analysis of stream terracing is the most recent contribution to the sub- ject,^ adds the amphitheater terrace, the junction terrace, and the fan ter- race. Such detail is not required in this connection, but it is proper to dis- ' Illustrations of Surface Gfology. By Edward Hitchcock, p. .'">. 'River-Terracing: its Metbods and their results. B> Hugh Miller. In Proc. Royal Physical Soc, vol. 7, 1883, pp. 263-^06. STEEAM TERRACES. . 81 tinguish the fan terrace from the lateral terrace, to which the ^diraseology of the preceding paragraphs more particularly applies. The fan terrace of Miller, as developed in a mountain country, has been admirably described and figured by Drew, who speaks of it as an "alluvial fan cut by a river", but gives no shorter title;' in the nomenclature of the present chapter it is an alluvial-cone terrace. Where a large stream flowing thi'ough an alluvial plain receives a small tributary from an upland bordeiing the plain, the tributary often builds an alluvial cone upon the margin of the plain. If afterward the large stream, shifting its course over the plain, encroaches on the alluvial cone, it con- verts it into a teiTace. The small stream acquires in this manner a lower point of discharge and is induced to corrade a channel through its own alluvial cone, dividing it into two parts. With reference to the valley of the small stream, these parts are lateral terraces. With -I'eference to the valley of the large stream, they constitute together an alluvial-cone terrace. The allu\ial-cone terrace differs from the lateral terrace in that its surface does not incline uniformly in the direction of the current of the stream it overlooks, but inclines radially in all directions from a jDoint at the side of the valley. The Moraine Terrace.- Wlicu au alluvial plaiu or alluvial conc is built against the side or front of a glacier and the glacier is afterA\ard melted away, the alluvial suiface becomes a terrace overlooking the valley that contained the ice. The constructing stream may flow from the ice and gather its allu- vium from the glacial debris, but it usually flows from the land. The slope of the alhn-ial plain is determined by the direction and other accidents of the stream. Where the plain adjoins the glacier, it receives whatever debris falls from the ice, and it may be said to coalesce initially with a morainic ridge. Its internal constitution is partly allu\'ial and partly morainic. If the morainic ridge is large, the plain does not become a moraine terrace. If it is small, it falls away when the removal of the ice permits the margin of the plain to assume the "angle of repose." 'Alluvial aud lacustrine deposits and glacial records of tbo Upper-Iodns Basin. By Frederic Drew. Quart. Jour. Geol. Soc. London, vol. 29, 1873, pp. 441-471, ^The alluvial fan of Drew is the alluvial cone of American geologists, and there would be some reasons for preferring fan to cone if it were necessary to employ a single term only. It is convenient to use them as synonyms, employing cone when the angle of slope is high, and fan when it is low. MON 1 6 82 LAKP: BONNEVILLE. Moraine teiTaces may lie classified, after the manner of moraines, as lateral and frontal. The history of the lateral type is illustrated by F\^. 1 7, representing in cross section the side of a glacier in an ojjen valley. The alluvium, a, is built up syn- chronously with the glacial debris, d, and the two interbed and mingle at their junction. When the ice melts, the face of the deposit assumes under gravity the profile indicated by the dotted line. If the glacier diminishes WmSm^m. ■;:,:.... ''.i,,;;:,?ImlmM:u....... '...da^i Flu 17. -Weal eectioii, illublratioy tliu furmation of a Moraine Tcrraco O'Vflduallv SUCCeSsivO terraCeS »t the .ShIo oi' a Glacier. " -^ ' are formed, and these fre- quently overlap. In Fig. 1 8 it is assumed that the ice profile had succes- sively the positions of the dotted lines x and y. When it retreated to y, the ac- cumulated depo.sit assmned the profile ahc^ and a new deposit began between the ice and the face he. By subsequent ice retreat the second depo.sit as- sumed the profile def. As a i-esult of this process the ma- terial of the terrace de overlies unconformably the material of the terrace db. 7, »-W^m^s^l Fig. 18.— Ideal sectioo, sbowing the internal structure of grouped Lateral Moraine Terraces. An alluvial plain bordering the front of a glacier is apt to overlap the ice and to include near its outer margin not only morainic debris but blocks of ice. When the ice melts, the overlapping de- posit cannot assume the simple earth-slope or angle of repose, but receives a hummocky, mo- FlG. 19— Jde.ll section of alluvial filliugagainst Front Edge of Glacier. rainic surface (Fig. 20). MORAINE TERRACES. 83 Fig. 20. — Ideal soctiou of Froutal Mor^iine Terrace. So closely does the moraine terrace simulate the stream terrace that it is usually undistinguished.^ The lateral type is identical ui cross-profile and in longitudinal profile, and, unless portions of the morainic ridge remain, has but one for- mal difference: the contours of its outer face, being determined by the side of an ice stream, are smooth curves of gentle flexure. The Fault Terrace.-It sometlmes occurs that two or moi*e fault scarps with throw in the'saine direction, run parallel with each other on the same slope, thus dividing the surface into zones or tracts at various heights. Each of these tracts contained between two scarps is a terrace. It is a dissevered section of the once continuous general surface, divided by one fault from that which lies above on the slope and by another fi-om that which lies below. It is the top of a diastrophic block, and its inclination depends upon the attitude of that block. Usually the block is tilted in a direction opposite at once to that of the throw of the limiting foults and to that of the general slope of the country. This has the eff"ect of giving to the terrace an inclination less steep than that of neighboring plains, or (exceptionally) of inclining it in the oppo- site direction. In the direction of its length, which always coincides with the strike of the faults, the terrace is not horizontal, but undulates in s}Tnpathy with the general surface from which it has been cut. The Land-Slip Terrace.-Tliis is closcly rclatcd iu cross-profile to the fault ter. race, but is less regular and is of less longitudinal extent. Its length is fre- quently no greater than its width. The surface on which motion takes place has a cross section outwardly concave, so that the sliding mass moves on an arc, and its upper surface, constituting the terrace, has a less inclination than in its original position. Frequently this effect is can-ied so far as to incline the terrace toward the cliff which overlooks it, and occasionally the ' Its recognition was p^ob.^bly late. W. S. Green describes it in " The High -ilps of New Zealand '' (London, 18S3), and Cbainberlin describes and names it in the Third Annual Report of the U. S. Geo- logical Survey, P- 304. The name " moraine terrace " w.as provisionaHy attached by E. Hitchcock (Sur- face Geology, pp. 6, 61) to a phenomenon not now regarded as a terrace. 84 LAKE BONNEVILLE. edo^e of the terrace is connected with the chff in such way as to fonn a small lake basin. An even terrace of such origin is rarely observed. The surface is usually Imininocky, and where slides occur in groups, as is their habit, the hillside is tlu'own into a billowy condition .suggestive of the surface of a terminal moraine. comparison.-The Only fcaturc by which shore ten-aces are chstinguished from all terraces of other origin, is the element of horizontality. The wave- cut terrace is bounded by a horizontal line at its up})er edge; the delta is bounded by a horizontal line about its lower edge; and the wave-built ter- race is a horizontal jdain. But the application of this criterion is rendered difficult ]>y tlie fact that the teiTUce of diiferential degradation is not infre- quently margined ))y horizontal lines; while the inclinations of the stream teiTace and tlic imiraine terrace, though universal and essential characters, are often so small in amount as to be difficult of recognition. The fault teiTace and land-slip ten-ace are normally so uneven that this character suf- ficiently contrasts them with all shore features. The wave-cut ternice agrees with all the non-shore terraces in that it is overlooked by a cliff rising from its upper margin, and usually differs in that it merges at one end or both with a beach, barrier, or embankment. It is further distinguished from tlie terrace of differential degradation by the fact that its configuration is independent of the structure of the rocks from which it is carved, while the latter is closely dependent thereon. In freshly formed examples, a further distinction may be recognized in the mode of junction of terrace and cliff. As viewed in profile, the wave-cut tenace joins the associated sea-clifi'by an angle, while in the profile Avrought by dif- ferential degradation, the terrace curves upward to meet the overlooking clifl". The wave-cut terrace is distinguished from the stream terrace by the fact that it appears only on the margin of an open basin broad enough for the propagation of efficient AAaves, whereas the latter usually margins a nar- row or restricted basin. In the case of broad terraces a fm-ther distinction is found in the fact that the shore terrace descends gently from its cliff to its outer marmn, whereas the stream terrace is normally level in cross section. In fresh examples the alluvial capping of the stream tenace affords addi- tional means of discrimination. COMPAKISON OF TERRACES. 85 The wave-cut ten-ace is distinguished from the moraine ten-ace by the fact that its floor consists of the preexistent ten-ane in situ, the moraine ter- race heing: a work of construction. The wave-cut terrace occurs most fre- quc'iitlv on sahents of the topography; its inner margin is a simpler curve tlian its outer. The moraine ten-ace is found most frequently in reentrants; its outer margin is a simpler curve than its inner. There are certain cases in which the wave-formed and stream teiTaces merge with each other and are dithcult of separation. These occur in the estuaries of ancient lakes, where the terraces referable to wave action are confluent with those pi'oduced contemporaneously by the lateral corrasion of streams. The stream being then tributary to the lake, it could not carry its erosion to a lower level, and its zone of latei-al corrasion was at its mouth contiudus with the zone of wave ero.sion in the lake. The wave-built terrace may be distinguished from all others by the character of its surface, which is corrugated with parallel, curved ribs. It differs from all except stream and moraine terraces in its material, which is wave-rolled and wave-sorted. It differs from the stream terrace in that it stands on a slope facing an open basin suitable f(n- the generation of waves. The delta differs from all except the stream terrace and the moraine terrace in its material and in its constant relation to a water Avay. Its mate- rial is that known as stream drift. Its mass is always divided by a stream channel so as to lie partly on each bank ; its terminal contour is a convex arc centering on some point of the channel ; and it is tisually confluent in the ascending direction with the nonual stream terrace. Indeed, when con- sidered with reference to the dividing channel, it is a stream terrace ; and it is only with reference to the lakeward margin that it is a shore tenace. It is distinguished from the noi-mal stream tei-race by its internal structure. The liifjh inclination of the lamination of its middle member — fonned by the discharge of coarse detritus into standing water — is not shared by the stream terrace, while its horizontal alluA-ium does not, as in the case of the stream terrace, rest on the preexistent terraue. It is distingui.shed from simulating I)hases of the moraine terrace by its outer contour, which is outwardly con- vex and more or less irregular, while that of the moraine terrace is straight 86 LAKE BONTfEVILLE. or simply curved. The frontal moraine terrace often affords a ttirther dis- tinction by the hummocky character of its outer face. As the formation of the delta is independent of wave action, it may and does take place in sheltered estuaries and in small basins. A small lake inteniipting the course of the stream may be completely filled by the extension of the delta built at its upper extremity ; and when this has occurred, there is nothing in the superficial phenomena to distinguish the fonnation from the normal flood plain. Tlie teiTace of differential degradation is further distinguii^hed from all shore terraces by the fact that, without great variations in width, it follows the turnings of the associated cliff, conforming to it in all its salients and reentrants. Where the shore follows an irregular contour, wave-cut ter- races appear only on the salients, and in the reentrants only wave-built teiTaces and deltas. RIDGES. Ridges are linear tojiogTaphic reliefs. Tliey may be broadly classed into (1) those produced by the erosion or dislocation of the earth's surface, and (2) those built upon it by superficial transfer of matter. In the first class, the substance of the ridge is continuous with that of the adjacent plain or valley ; in the second, it is not ; and this difference is so obvious that shore ridges, which fall within the second class, are not in the least liable to be confused with ridges of the first class. They will therefore be compared in tliis place only witli other imposed ridges. Of shore plienomena, the bar- rici-, the embankment, and the rampart are ridges. They will be contrasted witli the iiKiraine and the osar. The Mora.nc.-The dctritus deposited by glaciers at tlieir lateral and termi- nal margins is usually built into ridges. The material of these is frag- meutal, heterogeneous, and unconsolidated. It includes large blocks, often many tons in weight, and these are angular or subangular in form. Some- times their surfaces are .striated. The crest of the moraine is not liorizoiital, but descends with the general descent of the land on which it rests. Moraines are found associated with mountain valleys, and also upon open plains. In the first case their crests are narrow, and their contours are in general remilar. The lateral moraines follow the sides of the val- COMPARISON OF RIDGES. 87 leys, often standing at a considerable height above tlieir bottoms, and are united by the frontals or terminals, which cross from side to side with curved courses whose convexities are directed down stream. The moraines of plains have broad, billowy crests abounding in conical hills and in small basins. The osar or Kame—Thcse uames are applied to an indirect product of glacial action. It is multifarious in form, being sometimes a hill, sometimes a ridge, and often of more complicated form. It doubtless embraces types that need to be sepai'ated; but it is here sufficient to consider only the linear form. As a ridge, its trend is usually in the direction of glacial motion. Its ma- terial is water-worn gravel, sand and silt, with occasional bowlders. Its contours are characteristically, but not invariably, irregiUar. Its crest is usually, but not invariably, uneven; when even, it is parallel to tlie base or to that upon which the base re.sts. In other words, tlie ridge tends to equality of height rather than to horizontality. Comparison. -The sliore ridges are primai'ily distinguished from the glacial ridges by the element of horizontality. The barrier and the embankment are level-topped, while the rampart has a level base and is so low that the inequality of its crest is inconsideraljle. It is onlv in exceptional cases and for short distances that moraines and osars exhibit horizontality. Sliore ridges are further distinguished by their regularity. Barriers and embank- ments are especially characterized Ijy their smoothness, wliile smooth osars are rare, and the only moraine with even contours is the lateral moraine associated with a narrow valley. Other means of discrimination are afforded by the component materials, and the moraine is tlius clearl}' diiferentiated. The barrier and the embank- ment consi.st usually of sand or fine gravel, from which both clay and larger bowlders have been eliminated. Except in immediate proximity to the sea- cliff whose ero.sion affords the detritus, tlie ]»t'l)bles and Ixiwldci-s are weW rounded. The material of the rampart has no sjK'cial qualities, but is of local derivation, the ridge being formed simply by the scraping together of superficial debris. The moraine contains heterogeneous material ranging from fine clay to very large, angular blocks. The materials of the osar are normally less rounded than tlK)se of normal shore ridges. 88 • LAKE BONNEVILLE. Certain osars of great length, even figure, and uniforai height are dis- tinguished from barriers by the greater dech%4ty of their flanks, and by the fact that they do not describe contours on the mai'gius of basins. THE RECOGXITIOX OF ANCIENT SHORES. The facility and certainty with which the vestiges of ancient water margins are recognized and traced depend on local conditions. The small waves engendered in ponds and in sheltered estuaries are far less efficient in the carving of cliff's and the construction of embankments than are the gi"eat waves of larger water bodies; and the faint outlines they produce are afterward more difficult to trace than those strongly di-awn. The element of time, too, is an important factor, and this in a double sense. A water surface long maintained scores its shore mark more deeply than one of brief duration, and its history is by so much the more easily read. On the otlier hand, a svstem of shore topography from which the parent lake has receded, is immediately exposed to the obliterating influence of land erosion, and gradually, though very slowly, loses its character and definition. The strength of the record is directly proportioned to the dura- tion of the lake and inversely to its antiquity. It will be recalled that in the preceding description the character of horizontality has been ascribed to every shore feature. The base of the sea-cliff and the coincident margin of the wave-cut terrace are horizontal; and so is the crest of each beach, barrier, embankment, and wave-built terrace; and they not merely agree in tlie fact of horizontality, but fall essentially into a common plane — a plane intimately related to the horizon of the maximum force of breakers during stonn.>^. The outer margin of the delta is likewise horizontal; l)ut at a slightly lower level — the level of the lake surface in repose. This difference is so small that for the purpose of identification it does not affect the practical coincidence of all the horizontal lines of the shore in a single contour. In a region where forests aff(jrd no obstruction, the observer has merely to bring his eye into the plane once oc- cupied by the water surface, and all the horizontal elements of shore topog- raphy are projected in a single line. This line is exhibited to him, not merely by the distinctions of light and shade, but by distinctions of color, VALUE OF THE DISTANT VIEW. 89 due to the fact that the changes of inclination and of soil at the line influence tlie distribution of many kinds of vegetation. In this manner it is often possible to obtain from the general view evidence of the existence of a faint shore tracing, which could be satisfactorily determined in no other way. The ensemble of a faintly scored shore mark is usually easier to recognize than any of its details. It is proper to add tliat this consistent horizontality, wliicli appeals so forcibly and eflectually to the eye, can not usually be veritied by instru- mental test. The surface of the "solid earth" is in a state of change, whereby the vertical relations of all its parts are continually modified. Wlierever the surveyor's level has been apijlied to a fossil shore, it has been found that the "horizon" of the latter departs notably from horizontality, being warped in company with the general surface on which it rests. The level, therefore, is of little ser^^ce in the correlation of shore lines seen at different places and not continuously traced; but when an ancient shore-line has been faithfully traced through a basin, the detennination by level of its variations in height discovers the nature of displacements occurring since its formation. It miglit appear that the value of horizontality as an aid to the recognition of shores is consequently "vitiated, but such is not the case. It is, indeed, true that the accumulated Avarping and faulting of a long period of time will so incline and di.sjoint a system of shore features that they can no longer be traced; but it is also true that tlie processes of land erosion will in the same time obliterate the shore features themselves. The minute elements of orographic displacement are often paroxysmal, but so far as observation informs us, the general progress of such changes is slow and gradual, so that, during the period for Avhich shore tracings can with- stand atmospheric and pluvial Avaste, their deformation is not sufficient to interfere materially with their recognition. CHAPTER III. SHORES OF LAKE BONNEVILLE. In the preceding- cliapter the features of a slnyJe desiccated shore-line are described; a shore-Hne, that is, Avith nothing above it on the sloping side of its basin except the varied topography characteristic of dry land, and noth- ing below it but the smooth monotony of a lake bottom. Proceeding now to tlie consideration of the Bonneville shores, we pass from the simple to the complex, for the Bounevir-; Basin is girt by nk;,ij shore-li' --, which form a continuous series. Only the highest of these is contiguous to land topog- raphv, and only the lowest encircles an area covered exclusively by lake sediments. The water has undergone changes of volume which have car- ried its surface and waves to every part of the basin from the bottom to an altitude of 1,000 feet. So much of the basin as lies below the highest shore- line has received lake sediments; and the geologic data comprised in these sediments are combined with the phenomena of the lower beaches in a man- ner that is at once instructive and complicated. The supei-jiositions of sIk ire- line upon lake sediment and lake sediment upon shore-line record a history of contracting and expanding lake area, the deciphering of which con.stitutes one of the chief subjects of our study. These will be discussed at lengtli in the sequel. Here it is desired merely to state the fact that for a vertical space f)f 1,000 feet on the sides of the basin, the evidences of lacustrine waves and lacustrine sedimentation have been imjiosed on the jjreexistent configuration of the countr}'. Lake Bonneville lay in the district of the Basin Ranges, and the whole configuration of the lantl above the shore-lines is of the Basin Range iy\y^- As described in the introductory chapter, that district is studded witli a great 90 EARLIER SCULPTURE SUBAERIAL. 91 number of small mountain ranges, standing in irregular or^ i-r, but with a nearly constant north-south trend. Between them are narrow valleys floored by detritus worn from their sximmits during the uncounted ages of their existence. At the foot of each range, and piled high against its sides, are great conical heaps of alluA-ium, each with its apex at a mountain gorge. At top these alluvial cones are separate, but loAver down they adjoin, and their bases coalesce into a continuous scolloped slope, the visible footstool of the mountain. The cones, like the valley floors, are composed of detritus eroded from the mountains, but their material is coarser. At the margins of the undrained valleys the cones merge by gentle curvature with the valley floors. In the higher valleys, which drain to the closed basins, cones from the two sides meet along the medial line, giving to the cross profile the form of an obtuse \y. Above the alluvial cones all is of solid rock, and the topographic fonns are hard and angular. Every water-parting is a shai-]) ridge, and every water-way is an acutely V-sha2)ed gorge. The ridge and the gorge are characteristic features of land sculpture, being carved only where rain and running water serve for erosive tools. The alluvial cone is an equally characteristic land feature, being formed only where running water throws down detritus, without itself stopping. They are all the distinctive and exclusive products of land shaping, and could never originate beneath a lake or ocean. These are the features exhibited by the Bonneville Basin above the higliest shore-line; and the same features can be traced continuously down- ward past the .shore-line and t() the bottoms of the once submerged valleys. If one stands at a distance and views the side of a valley, he will see that each of the great alluvial cones is traceable within the zone of submergence almost as distinctly and quite as surely as above it. Its curving contour formed a part of every individual shore of the series. So, too, of the mount- ain gorges and ridgvs; wherever they extend below the ancient water limit the shore-line can be seen to follow their contours in a manner demonstrat- ing that they were already in existence when the lines were drawn. The preexistent topography of the Bonneville Basin was therefore of ten-estrial type and of subaerial origin. The sea-clifl"s and embankments and sediments of the lake were carved from and built on and spread o^•er a 92 LAKE BONNEVILLE. system of reliefs which originated at a time anterior to the lake, when the drainage of the mountains descended without obstruction to tlie bottoms of the valleys. In this respect, and in other respects to be developed further on, the pre-Bonneville conditions were identical with the post-Bonneville. Illustrations of this general fact could be adduced almost without limit, for they are afforded by all the slopes of the basin, liut a few will suffice. In Plate VIII there appea?-s at the right a portion of the western front of the Frisco Range. The crowded and uneven contour lines mark the posi- tion of steep-faced rock undergoing erosion. At the foot of the range is a system of alluvial cones, represented by contours with smooth curves and regular spaces. Still lower are the contours produced by wave action, and lowest of all is the outline of a playa. A moment's attention will show that tile great alluvial cone at a, which, like a trunk glacier, is compounded at its head of a number of single cones, is i-epresented at the base of tlie slope by the convexity at r. The cone h appears, though less plainly, at f; and the cone d appears at /;. Tlie cone c is greatly disguised at g, being loaded with a group of embankments; but it is probable that it has had sometliing to do with the deflection of shore-currents whereby those em- Ijankments were originated. Conversely, the indentation at j represents the unbroken I'ock-face at i, where for a space of half a mile no debris-convey- ing gorge issues from the mountain; and the dearth of detritus in the region A- is represented by the indentation at /. The map also suggests, what a study of the ground demonstrates, that the material built into embankments was derived by the paring away of the coast to the north of each localit}- of deposit. Considered by themselves, the monuments of the waves' activity are by no means inconsiderable; each group of embankments contains some hundi-eds of millions of cubic yards of gravel; but they sink into insio-- nificance when compared with the stupendous monuments of alluvial activ- ity on which they rest. They are mere appendages, and the erosion of their material from the adjacent slopes has by no means obliterated, though if has somewhat defaced, the alluA-ial forms. Granite Rock, an isolated mountain of the Salt Lake Desert, has at its north end a gorge di\-iding the extremity into two narrow spurs. About these spurs the Bonneville waters rose to a height several hundred feet LAJ3 BONNrvlLLE FI, vm \ / MAP OF THE EAST siDi-; OK ri;i:rss vai.i.k^' A S IJ WrsI I'lasc (if l'"risc-() M (ui 11 lams . I'liih. Sluiwmy I'cIhiioii nl' S1I()!!I-: KMIiAXK'MKN'TS MJ.rVlAl. CONES. Bv i; K ('.lUiiTl I 5 :. A L ; 'III ! I/fill: ')0'l',;-t (\,iil,'in:< i<. ■ -^ - t'V'"V\ \\U' \l\ i i ^ '^v Nil .-- , '■■ "^ \ "■ \\ \\W.\^ Ax\\\\V\v\^ \ \, \ \\\\\\\<>ci .Ixli.i:. Hm-c ,\ r.,.1,1 Drcwii livC Thoui)>knLi LAND SOAPING BEFOUE SHOKE SHAriNG.. 93 above any alluvial accumulation. All about the spurs theiv; is a distinct terrace cut in the granite at the highest water level, and the same can be traced, less continuously but still unmistakably, along the sides of tlie gorge to its head. This relation could not subsist had not the gorge and the sjiurs been carved out in substantially their present form before the waves attacked them. Bradley, speaking of the canyon of Ogden River, says ; It i.s evident that, when this canyon was origiually excavated, the Great Salt Lake was not far, if at all, above its present level ; so that the rushiug torrent which wore out this old rouuded bottom met no check until it had pa.ssed entirely beyoud the moutli of the canyon. There followed a time when the lake tillcil nearly or quite to its highest ter- race ; and, meanwhile, the Ogilen River continued to bring down the sand and pebbles which it had before been accustomed to sweep out upon the lower terrace, but now, checkeil by the ri.siug lake, deposited them in the lower parts of its old channel, until they accumulated to a very high levi'l, not yet accurately located. Again, the lake retired, and the stream again cut down its channel, sometimes reaching its old level and sometimes not.' In each of these localities the subaerial work antecedent to the lake epoch has greatly exceeded in amount the lacustrine work ; and the last has in like manner exceeded the subaerial work subsequent to the lake epoch. Disregarding tlie rate at which the several processes are carried on, it is evident that the construction of the alluvial cones of Frisco Mountain is a greater work than the btiilding of the embankments that ornament their flanks ; while the preservation of the embankments shows that little alluvial accumulation has since been made. Tlie carving of the spurs and gorge at Granite Rock implies the decay and removal of cubic miles of granite, while the production of the shore terrace involved the excavation of only a few thousand yards of the same rock. THE BOXXEVILLE SHORE-ilXE. The shore-lines of the series in the Bonneville Basin are not of uniform magnitude. The water rose and fell step by step, but not with equal pace, and at a few stages it lingered much longer than at others, giving its waves time to elaborate records of exceptional prominence. One of the excep- tional records is that which holds the liighest position oa the slopes ; and to ' U. S. Geot. Siirv. of Terr., Ann. Kept, for 1872, p. 196. 94 LAKE BONNEVILLE. this one, par excellence, the name Boune^•ille has been applied. It marks the greate.st e.xpanse of the ancient lake, and forms the boundary of the area of lacustrine phenomena. Al)ove the Bonneville shore-line the whole aspect i.s that of the dry land — here, an alternation of acutely cut water parting.s and water ways; there, huge, rounded piles of alluvium; the first stream-carved, the last stream-built; and each presenting to the eye a system of inclined profiles. Below the shore-line, the same oblique lines are to be found, but with them are an al )undance of horizontal lines, wrought by the waves at lower levels — i1r' terraces, beaches, barriers, and embankments of hiwer shore-lines. Except in sheltered bays, where the waves had little force, and except on smooth, mural cliffs of rock, where a beach could not cling and where the waves were impotent for lack of erosive tools, the contrast between wave work and stream work is strong, and the line separating the two types of earth-shaping is easily traced. If the Bonneville shore-line were far less deeply engraved than it is, it would still be conspicuous by reason of its position. As it is, no geologic insight is necessary to discover it, for it is one of the pronounced features of the country. It confronts all beholders and insists on recognition. The tourist who visits Ogden and Salt Lake City by rail sees it on the Wasatch and on the islands of Great Salt Lake, and makes note of it as he rides. The fanner who tills the valley below is familiar with it and knows it was made by water; and even the cow-boy, finding an easy trail along its terrace as he "rides the range", relieves the monotony of his existence by hazarding a guess as to its origin. The altitude of the Bonneville shore-line is about 1,000 feet above Great Salt Lake and about 5,200 feet above the ocean. In defining it as the highest shore of the basin, I have assumed the coiTectness of the more prevalent view of a mooted question; but before proceeding farther the op- posing \aew should be considered. THE QUESTION OF A HIGHER SHORE-LINE. It has been announced by Peale^ that there is e^-idence of a Pleistocene lake in the BonneA"ille Basin with a water level from 300 to 600 feet above the Bonneville shore-line, or from 5,500 to 5,800 feet above the sea. "On ' Tlir .\i)cicut Outlet of Great Salt Lake. By A. C. Peale, Am. Jour. Sci., 3cl series, vol. 15, 1878, pp. 4jy-444. A DISCREPANCY OF OBSEKYATION. 95 lidtli sides tif the Portneuf Avliere it comes into Maivsli Creek Valley an upper terrace is seen, and in 1872 Prof. Y. H. Bradley also readily identi- iied an npper terrace in the Marsh Creek Valley at the level of about 1, (»()() feet above the stream. In Gentile Valley and in Cache Valley also, traces of this upper ten'ace exist." In the passage referred to,^ Bradley mentions this terrace in connection with stream terraces, but does not speak definitely of its origin. Its interpretation as a shore feature therefore rests with Peale, who regards it as identical with the one observed l)y him "on both sides of the Portneuf." It has not been seen bv me, but I am by no means sure that in seeking it I succeeded in following Bradley's route. With more con- fidence it may Ije asserted that Marsh Valley is not contoured by any well- marked shore-line. I was careful to study its slopes from stations at various levels and under favorable atmosphenc conditions, and I failed to discover even the faintest trace of wave work. The same careful search was made for high-level shore traces in Cache Valley and Gentile Valley, but none were found. There are indeed terraces in Gentile Valley, and these are elsewhere mentioned by Peale, who found their altitudes 5,526, 5,242 and 5,186 feet;^ but they are stream ten'aces, not shore terraces. It is with reluctance that I record not only my inability to rediscover phenomena which another has reported, but also my opinion that his reported discovery was based on an error of observation; but the question here in- volved is of such importance in its relation to the Bonneville history that it can not well be ignored. As set forth in the second chapter, there are various other tyjies of ter- races liable to be mistaken for shore terraces; and the ranging of shore ter- races and other wave-wrought features in the same horizontal line, or plane, is a characteristic of great importance in their discrimination. To the ob- server Avho places himself in that plane and views the distant hillside at his own level, certain elements of the various shore features appear united in a horizontal line. If he selects for his observation an hour when the distrilju- tion of lights and shadows gives strong expression to the details of the con- figuration, he is able to detect a shore record so faint that he might cross and recross it repeatedly without suspecting its existence. Having searched ' Kept. U. S. Geol. Survey Terr, ^r 1H82, pp. SC'-aOS. ^Ecpt. U. S. Geol. Survey Terr, for 1877, WashiDgtoii, le79, p. 601. 96 LAKE BONNEVILLE. with distant ^^e^v and selected light for the reported high-level shore traces in Marsh and Cache Valleys, and having failed to discover them, I am satis- fied that Peale misinterpreted tei-races formed in some other way. Tlie matter is not fully set forth by the recital of the conflicting obser- vations. The Valley of Marsh Creek falls outside not only the Bonne\'ille Basin but the Great Basin. It is di-ained to the great j)lain of the Snake River by a deep and rather broad canyon which bears the marks of antiq- uity. The sides of this canyon, though of crystalline and schistose rocks, are not steep, and at the most constricted point there is a flood-plain a thou- sand feet broad. If there was, as Peale supposes, a barrier at this point containing the ancient lake, then its cutting must have consumed a long })eriod; and it is incredible that shore teiTaces have survived the contem- poraneous general waste of the surface. If there was no barrier at this point, tiien the supj)osed lake was a great inland sea, flooding the plain of the Snake l^i^ er, and its shore tracings on the margins of that plain should have been niucli more conspicuous (by reason of the greater magnitude of its waves) than any drawn in Marsh Valley, — but they have not been discovered. ]\roreover, a body of water capable of forming the supposed shore ter- races in Marsh Valley would have extended not only to Cache and Gentile Valleys but to the Great Salt Lake Desert, and the work of its waves should l)e visible, if anywhere, on the face of the Wa.satch Range. In that region, the conditions for the generation of large waves are far more favorable than in the relatively narrow valley of Marsh Creek. Nevertheless, a higher line has not been observed on the margin of the greater basin. Not only has Peale failed to record it there, but Bradley, Howell, Emmons, Hague, and King have expressly noted the Bonne^^lle as the highest shore-line.' It may be objected that the failm-e of these numerous observers to de- tect an upper shore-line is negative e^■idence merely, and should be given little weight in comparison with a single positive observation. But the fail- ure to detect is in this case something more than a negation. Subaerial land sculpture is as positive a fact as wave-wrought shore sculpture; and the as- ' F. H. Bradley, U. S. Geol. Surv. of Terr. Ann. Kept. 1S72, p. 192 E. E. Howell, U. S. Geol. Surv. West of tbe inOth Meriilian, vol. 3, Geology, p. 250. S. F. Emmons, U. S. Geol. Explor. 40th Parallt-l, vol.2, Descriptive Geology, p. 441. Arnold Hague, Idem. pp. 421, 423. Clarence King, U. S. Geol. Explor. 40tli Parallel, vol. 1. Systematic Geology, p. 491. U S. GFOLOGTCAL SURVEY •i — THE GREAT KAR LAKE BOXXKVILI.E PLATE IV TOCKTON. UTAH. NEGATIVE EVIDENCE. 97 sertion that the Bonneville is the highest shore-line implies the assertion tliat above it the topography is of the ordinary dry land tyjie. Every recogni- tion of an ancient shore is based, consciously or uncousciousl}-, on an ac- quaintance with the ordinary characteristics of the features of the land as well as with the pecuHarities of shores; and ability to discriminate the pres- ence of wave sculpture implies in the same degree ability to note its absence and its limits. The sujiremacy of the Bonneville shore has been recognized not only by many observers but in a great number of localities, and an induc- tion resting on so broad a basis may justly demand of a conflicting obser- vation the most rigorous verification. If the reader will turn to Plate IX he will be able to realize the weight of this evidence. The view presents the Bonneville shore at the pass be- tween Tooele and Rush Valleys. The observer stands on the west side of the pass and looks eastward toward the Oquirrh ]\Iountains. At the left lies Tooele Valley, open to the main body of the old lake. At the right is Rush Valley, which held a sheltered bay. The greatest wav^s came from the north, and, beating on the southeast shore of Tooele Bay, carved out a long line of sea-cliffs. The debris was at the same time diifted southward .... ' part of it being built into a free spit 7,000 feet long and 150 feet high at the extremity, and another part being accumulated during lower stages of the lake in an inniieuse Ijay-bar, oljstructing the pass. The spit appears in the pictui-e at the right, following the base of the mountain. The bay-bar extends from the center of the view to the foreground. It will he observed that the line of sea-cliff at its most distant point impinges on a spur of the mountain ; and at its southern end, near the middle of the picture, it touches another spur, while in the interval it crosses only the alluvial slojje. There could scarcely be a greater contrast than between the sculpturing of the mountain-spurs above the line of sea-cliffs and the smooth contours of the slopes below that level. The cliffs are here of rather unusual height, and the shore embankments are of exceptional magnitude, so that the separation between subaqueous and subaerial topography is more than ordinarilv dis- tinct. This fact does not weaken the evidence that the Bonneville shore-line is the highest, but gives it greater stj'ength. For, if the water had occupied a higher level in Pleistocene time, the waves would have been able to record MON I 7 98 LAKE BOXNEVILLE. it at thi;? point by a i^hore-line of unmistakable definition. If shore traces of a greater lake are anywhere preserved they should be found at such a point as this, where the conditions for wave beating are exceptionally favorable. The same lesson may be learned fi'om Figure 21, and from the views on ^ ^"^5^^i^**^^2?r^^ ^^B- . k-JWb-a- '■-^i'^. ^5^^ ^^ rS -^^'^^^'--rf^'^' --f^n^ Fio. -1. — Bouueville and Tutermediiiif »-njbaiikin>-iit.^ near ^^^ Usvillc, L't.ib, (ilmwinj; coDIra3t bttwteu Littural aud Subaerial Topo^rraphy. Plates XXI and XXII, representing the shore topography and mountain topography at Wells\'ille and Dove Creek. MORE ANCIENT LAKES. Although Peale's supposed discovery is unverified, and though it is believed that an exhaustive investigation would prove it to be illusory, it is nevertheless true that some or all of the mountains of the Bonneville Basin were girt by shore-lines long before the BouneWlle epoch, and that if these shore-lines were extant they would, in some places at least, lie higher than the Bomieville. The mountains against which Lake Bonne^^lle washed are relatively very old, so old that they were greatly eroded before Tertiary time. Ever since their first uplifting they have been wasted by ero.sion, and during at least a portion of the time the detritus worn from them has TEKTIAEY LAKES OF THE B02sXEVILLE BASIX. 99 been received by the interjaceut valleys. The degradation of their crests and the burial of their bases would long ago have obliterated them had they not been preserved by a series of supplementary u})liftings, which, like the' original, were differential, not being shared by the intervening valleys. In the region of the Great Salt Lake Desert, where a plain has been formed by the coalescence of many valleys and the local burial of the ranofes, the depth of detritus must be several miles.' Of the constitution ol' this depos- ited mass nothing is known by direct observation. It is smoothly covered by the sediments of Lake Bonne\'ille, and no section is exposed. But indi- rectly we are shown that some i)art of the debris was spread under water, for the uprising mountain ranges have carried with them here and there, clinging to their flanks, small patches of lacustrine strata. It is believed that four separate groups of lake beds have been thus distinguished. The first of these occurs in the southeastern part of the basin, and probably touches the shore of the ancient lake only in the estuary of the Sevier River. No fossils have been found at that point, but there is little reason to doubt that the strata were once continuous v,^t\\ the Pink Cliff formation, which covers large areas farther east, and has been classed as early Eocene. The principal locality of the second is the eastern base of the Ombe Range, where an isolated -outcrop of barren strata resting against the mountain dips abruptly beneath the later sediments of the desert. These strata have been correlated on lithologic grounds with fossiliferous beds farther west, and are regarded by the geologists of the Fortieth Parallel Survey as of Middle Eocene age. The third group, though 3nelding no fossils, is believed to be Neocene. It was first noted by Emmons in Rush Valley south of the Great Salt Lake Desert, and has since beeu found at the narrows of the Jordan River, at Salt Lake City, at the north edge of the desert near Matlin, and at the extreme northwest corner of the basin in Cache Valley, whence it extends across the rim of the basin into Marsh Creek Valley. The strata of the fourth group, known chiefly from the investigations of King and Hay- den and their as.sistants, occur at a number of points along the northern margin of the plain, and are believed to appear also north of the divide in districts now di-aining to the Snake River. From Morgan Valley to Cache Valley they occupy a trough between two divisions of the Wasati-h Range. \ 100 LAKE BONNEVILLE. Oh the low northward continuation of the main Wasatch ridgC-, where it separates Cache and Malade Valleys, they are seen to be wrapped around a ■ series of low crags of Paleozoic rocks ; and it is evident that they have been raised to their present prominent position by the relifting of an ancient crest. On the east side of it they have been upturned by the displacement so as to dip at a high angle beneath the Bonneville lacustrine beds of Cache Valley. On the west they are sejiarated from their original continuation beneath Malade Valley by a fault, the tln-ow of which is probably more than 1,000 feet. Their relation to the third group has not been established, and it is possible that they constitute a part of the same series. The local- ity of the fifth group is just north of Salt Lake City, where an epaulette of Tertiary gravel and sand rests on a jutting shoulder of the Wasatch Range. This fragment is completely suiTounded by faults, its eastern continuation ha^nng been lifted high in air and obliterated by erosion, and its prolonga- tion in every other direction having been dropped so low that it is at once preserved and concealed by the deposits of the plain. This, too, is unfos- siliferous ; and it is here assigned to the upper Neocene merely on the strength of its structural relations. It is needless to enter upon these at this place ; but it should be remarked that the same relations, considered from another point of view, led King to surmise its Eocene age. Each of these lakes made its contribution to the filling of the basin, receiving, sorting, and spreading the debris from the wasting mountains; but neither can in strictness be called the predecessor of Lake Bonneville, for neither was confined to the area of the Pleistocene basin. So far as in- dicated by observed outcrops, the oldest Eocene lake lay almost entirely outside the Bonneville area; and it may have existed at a time when the greater part of that area was dry land. The second stretched westward far beyond the present di-ainage of the Salt Lake Desert, and may have over- lapped the Bonne\alle Basin but slightly. The third and fourth encroached nortlnvard on the drainage of the Colmnbia River. Too little is known of the fifth to indicate its relation to the Bonneville Basin. Their record is exceedingly fragmentary, but if it were full it would still give an imperfect history of the basin in Tertiary time, for there is no reason to believe that they represent more than a small part of that time NO TERTIARY SHORE-LINES. 101 Tliey tell us, however, that the phj'sical mutations of the period included numerous local elevations and depressions, wliereby the di'ainage of the country was repeatedly revolutionized; it was diy land at one time and and lake basin at another. It is quite possible that the lakes were excep- tional j)henomena, and that the prevailing condition was one in which the whole area drained to the ocean. It is equally possible that the BonneA-ille Basin continuously held a lake which, as the land rose and fell unequally, was expanded and contracted, now in one direction, now in another. The character of the lake beds and their relations to the mountains, show in numerous localities that the ranges were not submerged. Waves must therefore have b^fiten on their flanks, and tlie cliffs, terraces, and em- bankments peculiar to shores must have been wrought, but of these there is no known vestige. When the structure of the mountains has been elabo- rately studied, so that those elements of their configuration which depend on the distribution of strata and on faults can be definitely indicated, it may be possible to point out dissected terraces and ruined sea-cliffs as remnants of Neocene shores; but for the present such vestiges are beyond recognition. A shore is of the most perishable of geologic phenomena. It is little more than a congeries of forms; and whether worn away by atmospheric agencies or buried by sedimentation, it ceases to be available as evidence of a water margin. OUTLINE OF THE LAKE. The outline of Lake Bonneville at its highest stage was intrioate. Its shores jjresented a succession of promontories and deep bays, and it was beset with islands. Its longer diameter lay north and south, parallel to the trend of the mountain rang^es of the district and to nearlv all the lines of geologic structure. Its general outline was I'udely pear-shaped, with the stem pointing southward. A straggling series of promontories and islands crossed it near the middle, dividing it into two principal bodies, of which the northern and larger covered the Great Salt Lake Desert, and the south- ern the Sevier Desert. . The long southward bay re]iresenting the stem of the pear, occupied the Escalante Desert. The main body was joined to the Sevier body by three straits, of which the deepest and broadest lay be- 102 LAKE BONNEVILLE. tween Simpson Mountain at tlie east and McDowell Mountain at the west, in the region now known as the Old River Bed. The Escalante Ba}- was connected with the Sevier bod}- by a long strait, most constricted at Ther- mos Spring. The following details are of local rather than general interest, but are essential to a full descrij)tion of the lake. They will be more readily fol- lowed by the aid of the large map accompanpng the volume. Tlie trend of the ranges gave character to all the major details of the coast, and tlie axes of the laiger i.slands, j^eninsulas, and bays lay approxi- mately north and south. Beginning at the north to describe them, we have first Cache Valley bay, an oblong sheet of water, tangent at one .side to the main body and there joined to it by a broad strait inteiTupted by several islands. Inside the bay were tlu-ee islands, Avhose positions are now marked bv Franklin, Cache, and Battle Creek buttes. The butte near Smithfield was likewise an i.sland at first, though finally connected with ilie land by a bar. The canycms of Bear, Cub, Logan, and Blacksmith rivers Avere occupied by inlets, and the Bear River inlet may have reached at first to Gentile valley. These were all gradually diminished by the deposits from the streams, and eventufilly the Bear River inlet was approximately, and the Logan com- pletely, filled. Malade Valley held a long bay iinming northward from the main body, and having an expansion where the towns of Malade and Samaria now stand. Parallel but smaller liays occupied the Pocatello and Blue Spring valleys and the valleys containing Hanzel Spring and the town of Snows-' ville. Park Valley was filled by a bay, exceptional in its east and west trend, and separated from the main body by a grouj) of islands. The Prom- ontory range was divided by a strait at the point where it is crossed by the Central Pacific Railroad, the north part being a peninsula and the south a narrow, rocky i.sland. Little Mountain, near the ioviTi of Corinne, was a small i.sland, and the mountain from which Ilanzel Spring issues made a group of islands. There were tlu-ee small islands near the site of Kelton, and one just south of Ter- race. The Oml)e range, including Pilot Peak, was an island, sheltering beliiiid it a bav or sound from which a nan-ow arm ran iiorthward to DETAILS OF ANCIENT GEOGRAPHY. 103 Tliousand Spring Valley, the extreme limit of the w'ater in a northwest direction. Of the existing islands of Great Salt Lake, Stansbury and Antelope were islands then, and Fremont barely showed its apex above water. Of the "lost mountains" of Great Salt Lake Desert, nearly all overtopped the flood. Silver Islet, Newfoundland, Terrace Mountain, Lakeside Mountain, Gi-anite Rock, and a half-dozen nameless buttes, were circled by rocky and inhospitable coasts, but the Cedar Range west of Skull Valley made a broad and low island, which, bleak and barren as it now is, we may picture as then mantled with verdure. The eastern shore of the main body followed the steep base of the Wasatch Mountains, and had a simple outline except at three points, where it was diversified bj' the estuaries of Box Elder Creek, Ogden River, and Weber River. Tlie Box Elder estuary extended nearly or quite to the little mountain valley where the Danish settlement of Mantua lies. Ogden Canyon was occupied by a long and narrow strait, communicating with a bay several miles broad, hemmed in by mountains. Through the canyon of the Weber a similar strait connected the main body of the lake with a small bay in Morgan valley, — a bay on wliich the Welder delta gradually encroached, but which was not comj^letely obliterated before the final subsidence of the water. The western shore of the main bf>dy followed the eastern base of the Gosiute range, and was characterized by an abundance of small islands. Its only estuary ran southward a short distance into Deep Creek Valley, stop- jjing several miles north of the settlement. Southward from the main body ran four long bays, two associated with the east shore and two with the west. The first of these, counting from the east, was divided by a close stricture into an outer bay and an inner, the outer covering the valley of the Jordan River and the inner spreading over Cedar, Utah, and Goshen valleys and a part of Juab Valley. In the inner bay the Goshen Hills made two islands, and the Pelican Hills cou.stituted one large and several small islands. ' Small estuaries occuj)ied Emigration and Little Cottonwood canyons, connecting with the outer bay, and the inner bay sent an estuary into Provo Canyon. The shallow arm in Juab 104 LAKE BONNEVILLE. Valley was nearly closed by one of the Goshen islands. It connected by the canyon of Salt Creek with the division of the hnj in Goshen Valley, and by the pass followed by the Utah Sonthern Railroad with the bay in Utah Valley. The second of the southward stretching bays was similarly constricted, its outer and c>j)en poi'tion covering Tooele Valley, and its inner, Rush Val- ley. Tlie two were nearly dissevered by the formation of a wave-built bar at Stockton. • Tlie third bay occupied White Vallev, a barren plain between the Con- fusion Range and the high part of the House Range. Its entrance was ob- structed by a rocky island consisting of the northern part of the House Range, and a long, crooked arm extending southward lacked little of com- nuinicating with a southerly division of the lake and converting the main part of tliie House Range into an island. The fourth bay occupied Snake Valley and was long and shallow, turn- ing eastward at its southern extremity. The Confusion Range east of Snake Valley, and the House Range east of White Valley, were massive peninsulas, joined at their southern extrem- ities to the western shore of the lake. A corresjjonding great peninsula on the east side was constituted by the Oquirrh, Aqui, Simpson, Cherry Creek, and Tintic mountains and their dependencies, and had a greater area than the State of Delaware. These peninsulas, together with the group of islands lying between them, separated the main bod}- of tlie lake from the Se^^er body. The group of islands comprised two of large size and about twenty of small size. The largest island was constituted by the Dugway Range and its southward prolongation. Drum Mountain; the second, by the ]\IcDowell I\Iountains. With the Sevier body were connected two long bays ninning south- ward and a number of smaller ones indenting the eastern and northeast , ern coast. Of the northern bays, one received the water of Judd Creek and another that of Cherry Creek. A third, occupying Tintic valley, was more constricted at the mouth and contained islands. A land-locked bay received the water of the Se-vier River and was partially filled by delta deposits. It was connected with the open lake by a narrow passage through SIZE OF THE LAKE. 105 the Canyon Range, comparable with the passage of the Hudson through the Highlands. Of" the soutliern bays, the shorter and more open occupied Sevier Lake Valley and Preuss Valley. The longer was narrow and irregular, filling the valley of Beaver Creek from George's ranch to Minersville, and extend- ing thence soutliAvestward into the Escalante Desert, where it was shallow. Its total length was about one hundred miles. The largest island of the Sevier Ijody was constituted by the Beaver Range, or Beaver Creek Range, which was separated by a narrow and tor- tuous strait from a peninsular tract bearing the Frisco and Picacho Mountains. There were two low islands a few miles broad close to the Avestern .shore, near Antelope S})ring. The apex of Furaarole Butte was slightly emergent, and so Avas the highest point of the contiguous lava mesa. Small islands marked the sites <^>f Pavaut and Kanosh buttes, and there were four rocky islands near the mouth of Escalante Bay, one of which is now represented by the more northerly of the Twin Buttes. In Escalante Bay there were five or six islands. EXTENT OF THE LAKE. The area of the Bonneville water surface was 19,750 square miles, a magnitude ranking it with the Laurentian lakes. A fifth part of this belonged to the Sevier body with its dependencies, and the remainder to the main body. Its length, measured in a direct line from Cache Bay to the south end of Escalante Bay, was 34G miles, and its extreme width, from the mouth of Sjianish Fork Canyon to a point on the Shoshone Range near Dondon Pass, was 145 miles. If its water surface were given a circular shape, its circum- ference would be 500 miles, but the actual length of coast, exclusive of isl- ands, was 2,550 miles. Its maximum depth was about 1,050 feet. The fol- lowing table will enable the reader to compare these dimensions with the corresponding dimensions of Great Salt Lake and the Laurentian lakes.' ' The .irea of Lake Bonneville was nieasureil by L C. Russell ; tbe areas, lengths, and widths of the Laureutiau lakes, by A. C. Lane. The length of a lake was, for this purpose, defined to be the length of the longest straight line terminated by two points of the lake shore ; its width, the greatest distance between shores iu a directioa at right angle to the line of tbe leugtb. 106 LAKE BONNEVILLE. Table I. Dmensions of Lakes. Bonneville. Great Salt. Superior. Huron. Michigan. Erie. Ontario. Area in sqnare miles 19, 750 •2. 170 31.500 23, 800 22, 300 9,900 1 7,250 Length in miles 340 63 377 • 247 330 246 197 1 Width in mi le» U5 51 170 216 106 58 67 1 Extreme depth in feel 1,050 t49 1,008 702 870 210 738 t At high stage. * In 1869 : near high stage. The^gi'eater part of the desiccated bed is an irreclaimable desert, but its eastern edge is the granary of the Great Basin. The Bear, the Weber, the Jordan, the Se-s-ier, and other triliutaries, fed by the snow-banks of a score of mountain ranges and plateaus at the east, carry their life-giving moisture to the genial climate of the lowlands, and a belt of oases is the result. If the water were to ri.se -again to its old mark, mure than one hun- dred towns and villages would be submerged and 120,000 persons would be di-iven from their homes. The Monnon temple at Salt Lake City would stand in 850 feet of water, and the temple at Logan, the metropolis of Cache Valley, would stand in 500 feet of watei\ Fort Douglas would be covered to a depth of 150 feet, Ogden 850, Provo 650, Kelton 1,000. Seven hundred miles of railroad would be immersed, and trans-conti- nental passengers would be transferred by boat either from Morgan City or from Spanish Fork to some point near Toano, Nevada, — a voyage of 145 miles for the northern route or 185 miles for the southern. The town of Fillmore would be half covered, the State House barely remaining on diy land, and Mantua, Paradise, Morgan, and Minersville wouL be lake ports. Heramon, Bingham, Ophir, Vernon, and Frisco would be peninsular towns ; and the mining settlements of Drum and Buell would be stranded on islands. SHORE DETAILS. The sinuosity of the coast and its diversity of slope and material give to the shore phenomena the utmost variety. Every t}iDical feature of non- tidal shores is A\ell illustrated, and some of the combinations are perhaps unicpie. The abundance of salients and reentrants, of promontories and inlets, has occasioned a large number of spits and bay bars, while long beaches and barriers are rare. SEA-CLIFFS OF BONNEVILLE SHORE. 107 At an early stage of the investigation, the writer thought that the coasts facing in certain directions gave evidence of exceptional amounts of wave work, and imagined that he had discovered therein the record of prev- alent westerly winds or westerly storms in ancient times. This belief was dissipated by further stud}- ; and he discovered, as students of modern shores long ago discovered, that there is a close sympathy between the magnitude of the shore features and the "fetch" of the efficient waves. The greater the distance through which waves travel to reach a given coast, the greater the work accompli.shed by them. The highest cliffs, the broad- est teiTRces, and the largest embankments are those wrought by the unob- structed waves of .the main body ; and opposite coasts appear to have been equally affected. The most interesting details of the upper shore-line are found at locali- ties where similar details affect the lower shore-lines, and it will be conven- ient to describe them in discussing the order of succession of the shores ; but certain features should be mentioned here. The greatest sea-cliffs are as a rule carved from headlands and fi'om the islands of the main body, but tlip highest of all occurs in the Jordan Bay at a locality known as the Point of the Mountain. For a distance of half a mile the cliff there has an aver- age height of one thousand feet, the eroded material ha%'ing been swept to the southwest ward and built into a magnificent spit, around the extrem- ity of which the Utah Southern Railroad winds in passing from Draper to Lehi. Another notable cliff occurs on the south face of a butte east of Dove Creek, and is ^-isible from the Central Pacific Railroad betAveen Ombe and Matlin. The eroded material was in this case swept eastward and north- ward, being earned about the angle of the butte, then an island, and dis- tributed in embaidiments on its eastern face. The cut-terraces of the Bonnevnlle shore are narrow as compared Avith those of one of the lower shore-lines. They rarely exceed a few rods in width. A good example can be found on the flank of the Wasatch Range just north of Big Cottonwood Canyon and others on the north end of the Oquirrh Range near Black Rock. These are mentioned as being easy of access, but they are less striking than some tluit are carved on islands at various points near the margin of the Great Salt Lake Desert. 108 LAKE BONNEVILLE. Spits are exceedingl)' numerous, being attached to nearly all of the ancient islands and to many of the salients of the main coast. Of those hining some magnitude, the most accessible are at Stockton (PI. IX), near Grauts\'ille, Tooele Valley (PI. XV), at the Point of the Mountain between Draper and Lehi, on Kelton Butte near Ombe station, and on the extremi- ties of the Terrace Mountains. Fig. 22.— Battf near Kelton, Utah. Embankments connecting islands with each other or with the main- land are to be seen at the west end of Park Valley, at Smithfield in Cache Valley, on Antelope Island in Great Salt Lake, a few miles east of George's Ranch south of Deseret, and at the eastern base of the Gosiute Range. V-sha])ed embankments are most numerous in Snake Valley, where no less than ten occur. Four are attached to the Simpson Mountains ojijiosite to the Old River Bed and others were seen in Preuss Valley and in Beaver Creek Valley. THE CUP UF CUP BUTTE. 109 Typical deltas are rare. Certain parts of the valleys of all the princi- pal streams were occupied by iidets or estuaries, and the heads of these inlets received alluvial deposits of the nature of deltas; but the process of accumulation appears usually to have been arrested before the deposit had extended to the oj^en lake : and afterward, when the lake receded and the streams resumed their work of excavation, all but scattered patches of the allu^^um was removed. American Fork, Spanish Fork, and Rock Creek built free deltas in the Utah Bay, and Spring Creek furnished one *to the shore of Cedar Bay, biit these were exceptional and small. At lower levels great deltas were constructed by many streams, and the deltas of the Bonne- ville shore are described in connection with these in one of the later sections of this chapter Plate VI exhibits a peculiar circular bar observed in a single locality only. The sketch is in part ideal, for there was no commanding point froin which to obtain the bird's-eye view necessary for the best presentation of the subject. Near the Old River Bed there is a group of quartzite buttes which were surrounded by deep water and formed a cluster of rocky islands. To the north and northwest the deep lake stretched unbroken for more than one hundred miles, but in all other directions land was near at hand. Each island butte shows a weather side facing the open water and a lee side fac- ing land. Each Aveather side is marked by a sea-cliff, which looks down on a broad terrace carved from the solid rock. The lee sides have no cliffs, but are embellished by embankments of various forms, built of the debris from the weather sides. In the case of the butte figured, the excavation of the platform was carried so far that only a small reimiant of the original island surAaved, and a comparatively small additional amount of wave work would have sufficed to reduce it to a reef From each margin of the sur- vi\ang crest, an embankment streams to the leeward, and the two embank- ments, curving toward each other, unite so as to form a complete oval. At their point of junction they are a few feet lower than where they leave the butte. Their material is coarse, ranging up to a diameter of two feet, and is conspicuously angular, exhibiting none of the rounding characteristic of detritus that has been rolled long distances upon a beach. Within the oval rim is a cup 38 feet deep, its sides and lip consisting, on the north, of the 110 LAKE BONNEVILLE. rocky slope of the butte, aud elsewhere of the wall of loosely heaped blocks of quartzite. If the material were volcanic, instead of sedimentary, it would be easy to imagine the cavity an extinct crater. Reservoir Butte, another island of the cluster, is figured in PI. XXIV, and further represented in PI. XXV and in Fig. 3 of PI. VII. It derives its name from a series of natm'al cups analogous to the one just described. These are attached to its steep slopes at various, levels, the process of con- struction ha%'ing been repeated at as many epochs in the history of the oscil- lating lake. In this connection, only the cups associated with the highest shore-lii.. will be described. The longer diameter of the butte trends north and south. At its northern extremity and along its northwestern face it displays a bold sea-clifi", from 50 to 1 00 feet high, springing from a terrace at the Bonne\'ille level several hundi-ed feet broad. On the eastern side the cliff and teiTace give place near the north end to a massive embankment, which first swings free from the side of the butte and then curves inward toward it, meeting it somewhat south of the middle. From the middle of the western side there starts a similar embankment, which, curA-ing through an oval arc of 150°, joins the butte at its southern extremity. The interval between the tenniui of the two embankments, a space of 1,000 feet along the southeastern face of the butte, was almost unaff'ected by the waves, being neither abraded nor covered by debris. The material contained in the embankments was derived exclusively from the weather side of the butte, and though each looped embankment joined the shore at two points, the conveyance of shore-drift along its crest appears to have been in one direction only. It is difficult clearly to reahze the process of this con- veyance, but there is no question as to the fact. In one case it left the shore at a small sahent, its course being there tangent to the contour, and, cur\-ing through an arc of 90°, finally assumed a course directly toward the coast, there almost precipitous. In the other case it left the shore at an obtuse salient, and before returning swung through so great an arc as nearly to reverse its direction. The cups witliin these loops have been somewhat silted up in" modern times, but still, except for then di-yness, they deserve the name of reser- voirs. The eastern was found to be 38 feet deep. The embankments were THE CUPS OF RESEKVOIR BUTTE. HI built in deep water and upon a foundation inclining steeply from the shore. Their forms are independent of the couhguration of their foundation. They were not accumulated from the bottom upward, but were constructed by successive additions at the end, the boulders being rolled along the crest of the embankment by the breakers and then dropped in deep water at its extremity. The outer face of the eastern bar has a height above its base of four hundred feet. EMBANKMENT SERIES. It might be inferred from the preceding description that the Bonneville shoi-e-liue was the product and is the index of a single uniform and continu- ous water stage. Indeed, it has been so regarded by every observer who has published an account of it, and the impression is readily and properly derived from its ordinary phase. There are, however, a few localities where the shore mark is distinctly resolvable, and shown to be compounded of several similar elements at slightly different heights superposed on one another. One of the most striking localities, and at the same time the one which first demonstrated the compound nature of the phenomenon, is repre- resented in PI. X. A rocky cape projecting fi-om the east shore of Snake Valley sheltered on one side a small bay opening to the south. Across this bay the waves built a series of bars, as represented in the map. The outermost of the series, that is, the one farthest from the land, is connected at its eastern end with a shore cliff labeled on the map " Bonne^nlle Sea- cliff"; and this cliff runs for some miles southward along the slope of the valley. ' A study of the locality demonstrated beyond question that the excava- tion occasioning the cliff and^its terrace, furnished the material for the bar, and furthermore, that the same cliff hue had pre%'iously been connected with each bar of the series. It will be readily understood that the inner bar was the first one to be built, and that the order of position is also the order «f age. They stand so nearly at the same level that no one of them could have been foi-med in the rear of another. Then- differences of level therefore record changes in the relation of the water to the land during the period of their formation. If 112 LAKE BONNEVILLE. we call the inner bar No. 1 and its altitude 11 feet, the series will be repre- sented by the following list : Feet. No. ] 11 No. 2 12 No.3 13 No. 4 : 4^ No. 5 4J Tett. No. 6 4i No. 7 8 No. 8 0 No. 9 0 No. 10 18 No importance is to be attached to the individuality of the bars. ^ There is a rhythm of action in the process of their formation which would prevent the construction of a continuou.s and even-tojiped tex-race under the most uniform conditions. If the bay had been so shallow that the same accu- mulation of shore diift would have abridged it twice as much, there might have been twenty bars instead of ten. The first three bars signify but a single epoch, duiing which the water stood at one level, or perhaps rose slowly. The next three, which in point of fact are but obscurely indiAnd- ualized, represent a succeeding water stage eight feet lower and possibly of somewhat gi-eater dui'ation. The seventh bar shows that the next move- ment consisted of a deepening of the water and was not long sustained. The eighth and ninth record the lowest stage of all, and the tenth the highest. The tenth contains so much more material than either of the others, being founded in deeper water and carried higher, that it must be considered as representing a longer time, and may be coordinated with either of the ante- cedent gi'oups. Outside the tenth bar the plain slopes gently lakeward, being inter- rupted within the area of the map only by a low bar, mdicated in the pro- file. _ This bar lies so far below the others that, if older, it might not have interfered with the wave action necessary to tljeir formation. Its relative age therefore does not appear. The process of construction is clearly demonstrated by the local details. The sea-clifi" was excavated from the alluvial foot slope of a mountain range. The derived material -consisted primarily of boulders, large and small, sand, and a certain portion of clay. The finer part was immediately washed lakeward by the undertow. That of middle grade was carried along the shore to the bay, and the larger boulders remained in situ until sufiiciently u 8.GE0LCoir.ij_ s'j; t ,*■ iif " '■ ^ 'J":!^.' i / / / " 'r^' r I II --'^~ //f^ x^ M A P OF I5.uiui;s or thk iu)N.\i:vii.lk siioi;!-: Near \hv Salt Marsli, iii Siiakf Vallrv, Itali Hv V D .Inliiisoll yy^^vTy,^ > ' ■'■■''■'''/c^.' lO'lWt Coutoun Fib Pi'ofile. le-r/iail Srutr thief times tlir Uuiizflrilul . Jul.u. ISirii A ru.lMl. Di awu hj r. Tl...inpB. SNAKE VALLEY BAY BARS. 113 reduced by attrition to be transported. In the bay the suiCiice currents Meri' concentrated by converging shores, and a powerful undertow was pro- duced, wlierebv a further separation was effected, the shore drift being de- prived of a coarser grade of del)ris than that previously eliminated, so that tlie matter actually deposited consisted of particles ranging from a half inch to four inches in diameter, — a clean shingle without admixture of sand. The sand and fine gravel thus eliminated by the undertow were deposited in large part near the head of the bay, causing the water to shoal rapidly, and ultimatelv determining the Ijreaker line to a new position outside the tirst, and thus initiating the construction of a new bar. In this way the deptli and length of the bay were at the .same time progressively diminished. I'or ])urposes of comparison the profile of the Snake Valley bars has lieen repeated in PI. XI, ^^ here a series of similar phenomena are also drawn to llie same scale. A brief descnption vriW be given of each locality. At the head of Skull Valley, a few miles north of Government Creek, there is a low alluvial water-parting separating the valley from the open desert at the west. At the time of the Bonneville water stage this pass was reduced to an isthmus only a few rods in width, and the Avater was shallow on each side. On the Skull Valley side there were formed a series of bay bars, represented in profile in the plate. The winds under the influence of which they weiv formed, could have blown only from the northward. The third ])rofile represents in similar manner a group of bay bars ob- served a few miles east of Sevier Lake. Tlie general trend of the old shore- line is there north and south, but at this particular spot thei'e was a small cove King on the north side of a rocky promontory. The bars were formed bv northwesterly winds. The fourth locality is a few miles east of the third, being on the oppo- site side of the Beaver Creek mountain range near George's Ranch. A small rocky hill was insulated at high-water stage by a narrow and shallow strait, and across this strait embankments were eventually Ijuilt l)y the north- easterly winds. The first of the embankments, however, did not coraj^letely close the passage, and remains as a spit, while the others are completed bars. The topographic relations are shown by Fig. 23. MON I 8 114 LAKE BONNEVILLE. The locality of the fifth profile is the southwestern angle of Tooele Val- ley, the constructive winds bloAving in this case also from the northeast. N^N-^ .f L-^-r>=;(-~^ ->._ 5^ ^ "^ -vs^ \ ■ Fig. 23.— Bars near George's lianch. Utah. The Dove Creek locality is far to the north of the others, being on one of the ancient islands south of Park Valley. Trains of the Central Pacific Railway pass it midway between Ombe and Matlin; and it falls within the area represented by PI. XXII. If the reader Avill turn to that plate, he will see that the Bonneville shore is represented on the southeastern face of the island by a sea-cliff and terrace, and on the northeastern by an embankment. The material for tlic embankment was dei'ived from the sea-clitf and carried around tlie angle 1\y shore action, doubtless by the alternating agency of winds from dift'erent directions. Below the Bonneville embankment there is a fine series of other embanlcments, which will be descnbed in a later section of this chapter. The surface of the island was eroded before the lake epoch, so that its .slopes consi-st of a series of ridges radiating in all directions. On the south- east face these were jjared away at the Bonneville level, reducing the shore to a straight clifi"; but on the northeast fiice, Avhere the action of the waves was constructive instead of destructive, the ridges retained their fonn, and the embankment was built across from one to another, enclosing a series of small basins occupied by lagoons. The first and second of these basins are now about twenty feet deep, and are undrained. The enclosing ])arapet is OTHER EMBANKMENT SERIES. 115 a sim|)le bar not susceptible of subdivision, the fonnative cuirents appear- ing to have held a uniform course during its construction. The tliird basiu is shallower, and a recently-fonned di-ain reveals a section of its parapet, showing it to consist of the three bars indicated in the lowest jjrofile of PI. XI. The cun-ent at this point must have been thrown farther and farther from the land as accumulation jiroceeded. The fourth basin is similar to the third, but the fifth has no inner bar. The low-lying inner bars are obAn- ousl y elder than tlie high outer bar, and all the minor features of the locality tend to the conclusion that, during the period of their formation, the train of shore drift did not extend to the fifth basin. It is inferred by analogy that there was an antecedent time, Avithin the e])och of the Bonneville shore, A\'hen the shore drift fiiiled to reach the third basiu, so that the series of bars there exhibted i.s incomplete. Let us now consider the question wliy tlie successively formed bars in these several localities differ in height. At least three general answers are possible. The embankments were built upon the land by means of the water of the lake, thrown into motion by the wind, and their variations in height may have resulted from variations of the wind or of the water or of the land. It is conceivable that the highest bars were produced by storms of exceptional force, and the lower ])y less violent storms. It is conceivable that the water of the lake rose and fell from tiine to time, and that the bars marked successive stages. It is conceivable that the land rose and sank, so as to bring diff'erent horizons successively within reach of the waves; and finally, it is conceivable that two or more of these causes conspired to pro- duce the phenomena. A movement of the land might have been general, involving the entire basin, or there might have been diff"erential movements, changing the rela- tive height at various points. In the first case the lake would be earned up and down with its basin, and there would be no change in the relation of shore and watei*. Tlie only land movement therefore Avhich could ])ro- duce the phenomena, is one of a diff"erential nature, and this would of neces- sity give rise to dissimilar results at widely separated places. If the sev- eral bar series are harmonious in their vertical relations, it is safe to say that they do not indicate oscillations of land. 116 LAKE BONNEVILLE. A movement of the water sm-face would evidently produce changes of the same vertical amount at eveiy ])oint, so that the hypothesis of lake os- cillation would be negatived if the several systems of differentiated bars were found to be inharmonious. The remaining hypothesis of unequal storm force may take two forms. In the first place, it might be imagined that each individual embankment of exceptional height was the creature of a single storm, or of a limited series of storms ; or, in the second place, it is conceivable that the general char- acter of the weather underwent secular variations ; so that from century to century there were notable changes in the maxinmm force of storm winds. Under the first Adew, we should anticipate that localities dominated by winds from different directions Avould not accord iu the character of their bar sj-stems ; the approximate coincidence of exceptional storms from oppo- site directions, being only adventitious, could not be expected to recur with uniformity. Under the second view, on the contrary, there would be uni- formity of result, — a general change of climate aftVcting all localities alike. The eolian hypothesis would therefore be disproved neither by the har- mony nor by the lack of harmony of the observed results. It a(hnits, however, of an indei)endent test of crucial x: ue. Great waves are unques- tionably able to tran.sfer coarser shore di'ift than .small waves, so that where the supply of debris is heterogeneous, the character of that selected for the construction of eiubankments is an index of the power of the waves. If, therefore, in localities where the shore di'ift is derived from the unsorted alluvium, it be found that the higher bars contain coarser fragments than the lower, it is j)roper to infer that they owe their superior height to su])eriority of wave force ; but if it be found that all the bars of a series are uniform in composition, their inequ.alities of size cannot be referred to variations of storm force, either local or general. As a matter of fact, there is no correlation of coarse material with high bars. The Snake Valley series was scrutinized with reference to this j)oint and found to be uniform in composition. AVe may then cease to consider the -sA'ind, at least so for as the more important variations are concerned, and limit attention to the hypotheses of land movement and lake movement. The theory of land movement would be sustained by a discordance among HYPOTHESES AND TESTS. 1 1 7 the systems of bars. The theory of lake movement would be sustained by an accordance. An imperfect accordance might indicate a combination of tlie land and lake changes. The facts are assemlilcd in PL XI, to wliich the reader is again referred. Each of the protiles represents a section at right angles to the system of bars it illustrates, and. all are drawn to the same scale, the vertical element being exaggerated three-fold. They are grouped on the page in such man- ner that the outer eml)anknients of the several scries appear at the right and fall in the same vertical colinnn. The first consideration affecting the comparison is that each series pre- sumably represents the same period of time, so that, if a correlation is pv niMi-e than one individual. The map is indebted to Mr. Gil- bert Tliompson for the details of the west coast between Deep Creek and Montello, and for the bays at the north ends of Pocatello ami ]Malade Val- leys, lie delineated also the details west of Sevier Lake and in the southern extension of White Valley. The map is indebted to Mr. Thompson and Mr. Albert L. Webster for the outlines of the Escalante Bay. Mr. Willard D. Johnson delineated the shores of the White Valley Bay and the coasts on the Dugway, MacDowell, and Simpson Mountains. The outline in Tintic Valley was furnished by Mr. H. A. Wheeler. Mr. Israel C. Russell mapped the bay east of the Canyon Range, and is responsible for most of the coast between Fillmore and George's Ranch. He contiibuted also numerous de- tails in all parts of the basin. Tlie remaining portions of the shore were mapped l)y me. Some idea of the distribution of resjionsiljility for the map, as well as of the thoroughness of the exploration, may be derived frt)m an examination of PI. Ill, where the routes of travel are exhibited. THE PROVt) SnORE-LiINE. Below the Bonue%'ille .shore-line ai'e numerous other shore-lines, amonjr which out' is conspicuous. Tlie name Provo Avas given to it on accmnit of a great delta, which is at once a notable feature of the shore-line and a ])i-om- inent element of the tt»pography of Utah Valley m the vicinity of the Un\n of Provo. The shore mark so far siu-passes in strength all others of the series that this character serves for its identification; and it has been recog- nized in all parts of the ba.sin without the necessity either of tracing its meander or of measuring its altitude. It has indeed been recojniized with confidence despite conflicting determinations of altitude, for it is neither '^/■j'.z b:?::"'.": IkUus B.C.-) A Ui .iHn bv G TI<..u>|»on THE PEOVO SHOEE-LINE. 127 uniform in height nor uniform in its vertical relation to the Bomle^•ille shore- line. In a general way it is 375 feet lower than the Bonneville shore and 625 feet higher than the water of Great Salt Lake. The Provo record is more recent than the Bonneville. This appears, first, from its state of preservation; the Provo cliffs are the steeper and shai-]ier and the smaller talus lies at their base. It appears, second, from the absence of lake sediments on the sm-faces of the Provo terraces. Dur- ing the formation of the Bonneville shore, the horizon of the Provo was sufficiently submerged to receive a layer of fine sediment; and a lake de- posit commensurate in amount with the .^Imre di'ift accumulated in the Bon- neAalle embankments would not escape detection if it had rested on the ten-aces of the Provo shore. The relative age is shown also l)y the relation of the shores to the outlet of the lake, as will be explained in another chajiter. The duration of the water stage recorded by the Provo shore Avas greater than that of the Boimeville water stage. Although the Bonneville is the most conspicuous of all the shore-lines, it does not exhibit the greatest monuments of wave work, but owes its prominence largely to its position at the top of the series, w here it is contrasted with topogi*aphic features of another type. There are several other shore-lines which rival it, and, al- though it probably outranks in magnitude all except the Provo, its discrim- ination would be a difficult matter were it an intermediate member of the series. The Provo, on the contrary, is rendered conspicuous chiefly by the magnitude of its phenomena. Its embankments are the most massive, and its wave-cut terraces are the broadest. j\Ioi-eover, the Provo Lake was in every way inferior to the Bonneville as a field for the genei'ation of powerful waves. It was narrower and shallower and obstructed bv larger islands. To have constructed shores equal to those of the BoiuieNillc, it must needs have existed a longer time; and still longer to have l)iiilt its greater stnict- ures. OUTLINE AND EXTENT. The outline of the lower shore was the less tortuous. The sinuosity of the Bonneville shore is due to the fact that the watir tloodcd a large num- ber of the narrow trouglis of the Great Basin and a\ as partially divided by 128 LAKE BONNEVILLE. the mountain ridges. When tlie water retreated to the Provo levcf; it al»nn- dmu'd a considcral)le number of tlie valleys and retired on many paits of the coast from the uneven mountain faces to the smooth c.intours of the alluvial slojtes. Two of the largest bays, .the Escalante and the Snake Val- ley, were comj)letely desiccated, and so was a third ])art of the Sevier De.s- ert. The water was withdrawn from Thousand Sj)ring and Buell Valleys, from Grouse Valley and Park Valley, from Ogden Valley and Morgan Valley, from Cedar Vall'V, Rush Vwlley, and Tintic Valley, and from Imth ends of Juab Valley. Of the three straits joining the Sevier body with the main body of the lake, only the eastern remained. The closing of the cen- ti-iil and western straits joined to the western peninsula the ishnids whicli ]i;id been constituted by the MacDowell and Dugway Mountains. The isLnids formed l)y the PnjUKmtory, the Cedar, and the Beaver Creek Kanges, were converted into peninsulas, and so was Pilot Peak. The group of islands south of Park Valley and the group south of Curlew were joined to the miiin- land; and it is possible that the islands constituted by the Lakeside Mountains were united to the Cedar Mountain peninsula. Doubtless many other hills that had ])reviously been submerged now ajjpeared as islands ; but none of these were of gi'eat extent, and the total luimber of islands must lune been greatlv diiiiinished. Among the emergent islands were sonu^ of the volcjiiiic buttes west of the to^^^l of "Fillmore and a basaltic mesa southwest of the town of Deseret. The passage from Cache Valley to the iiuiin body was reduced to a naiTow strait only a few hundred feet in width, and the entrances to the Utah Lake bay and the AVliite Valley bay were greatly restricted. SHORE CHARACTERS. In several res])ects the newer shore-line has a different facies from the older. It has already been remarked that it is more freshly cut. It is char- acterized also by its broader terraces, by its deltas, by its tufas, and by a peculiar dujdication in its jjrofile. While the Provo cut-terraces are far broader than the Bonneville, the associated sea-cliffs are not so high, the difference being occasioned, in part at least, by the relations of the two water surfaces to the general slo^oe. If a • THE PlIOVO TERRACES. 129 profile l)e drawn acmss any of tlie valleys occupied ])y the lake, it will be found to l)e broadly U-sliapcd. The floor of each valley is nearly flat ; and the alluvial slopes at the sides, rising very gently at first, gradually in- crease their inclination initil they join the acclivities of the mountains. The BonneA-ille and Provo shores su-e so related to the valleys that their diff'er- ence of a few hundred feet of altitude corresponds to "a general and notable difl'erence in tlie slopes of the land at their margins. The Provo waves, attacking comparatively gentle slopes, produced terraces of great Avidth, as the companions of cliffs Avith but moderate height. Floors 200 to 400 feet broad are of frequent occurrence; and in one place a cliff 75 feet high overlooks a terrace 750 feet wide. KiG. 24 — LirucBlouu buttu near Ruddicg Spring, Great Salt Lake Desert; au island at the Provo stage. Deitas.-Tlie abundance of deltas on the Provo coast requires for its ex- planation a considerable chapter of the history of the lake. It has already been remarked that the principal streams tributary to the basin rise at the east. In flowing westward each of them encounters one or more mountain ranges, across wdiich it passes in a deep and narrow defile or can- yon. The drainage system is older than the lake; and this series of canyons was completed by the streams before the Bonneville ejioch, so as to foiTu MON 1 9 130 LAKE BONNEVILLE. • jjait of the fjystein of valleys flooded by the lake. When the water first rose to the Bonneville level, it set back a number of miles into each of the canyons; and in .some instances extended beyond the first mountain range, forming' small bays on the eastern side. During the period represented by the Bonneville shore-line, the detritus brought by the rivers was tlu-own into these bays and inlets and gradually reduced their dimensions. A few of the smaller inlets were completely filled; and in three or four instances small deltas were j)rojected in'to the lake; but the remainder of the canyons retained the character of inlets until the Avater fell. At the beginning of the Provo epoch it is pn^liable that nearly all of the larger canyons atbuitted short estuaries, but of this there is no definite record. If such existed, they were quickly filled by alluvium, — the preexisting accmnulatious at the heads of tlie canyons affording an aljundant supply ready at hand. The fomia- tion of a delta in the open lake must have begun at the mouth of each can- yon soon after the establisluncnt of the water stage; and it was continued until the close of the Provo epoch. The water suriace then fell once more, " and the lowering of the mouths of the streams caused them to begin the erosion of the deltas; Ijut the broad terraces built on the open plain were not so easily effaced as the alluA-ial deposits v^-ithin the narrow canyons, and the destmctive activitv of the streams has accomplished only the opening of teiTaced channels through them. The channeling of the deltas was accompanied by the construction of other deltas at lower levels, so that each river course is margined by a series of deltas embodj-ing a portion of the history of the progi'essive changes of the lake. In the discussion of these series in a later section, the several deltas of the Pi'ovo shore will receive separate mention and descrijition. Calcareous tufa has been found in association with many of the shore- lines and was jirobal^ly deposited in some amount at all stages of the lake. It is exceptionally abimdant at the Provo level, but it will be more con- venient to describe its occuiTeuce in a special section devoted to the subject of tufa. The underscore.-AMiere tlic Provo water mark is a work of excavation, its characteristic prc)file includes two sea-cliffs and two ten-aces. The ujiper cliff is the greater of the two, and the teirace at its foot is the broader ter- THE UNDERSCOEE. 131 race. The lower terrace is rarely more than a twentieth part as great as the upper, and in many places it could not be detected. The vertical space between the two shelves is estimated to range from five to twenty feet; at tlie sole point of measurement it is six feet. The main ten-ace is conspicu- ously distinguished by its flatness. At no other stage of the lake have the waves cai-ved out so level a platfonn. In its broader examples the lake- wai-d slope is barely perceptible to the eye; and at no point does the total descent from the foot of the upper cliff to the crest of the lower exceed five feet. Tlie lower teiTace has no idiospicrasies aside from its association with the upper, but that peculiarity has caused it to be styled in the field note- books "the underscore," and it will be convenient to retain the designation. Though not universally discernible, yet it is so persistent a featm-e as to be found ser^-iceable in the identification of the Provo shore at doubtful points. EMBANKMENT SERIES. ^Miere the water mark consists of works of construction its characters are less constant. As a rule, the bays of the Provo coast ai-e spanned by single bars ; and its spits, like those of the Bonne^-ille shore, are apparently simple in structure; but m a few instances the accumulations in bays are observed to consist of two bars with the outer lower than the inner. The difference of height was never subjected to measurement ; but Avas estimated to be about fifteen feet. At Dove Creek (see PI. XXII) the shore exhibits two wave-built ten-aces, of which the outer and later formed is 14 feet lower than the inner. On Terrace Mountain, a few miles south of Ombe station, the Provo em- bankments hi a small bay are separated after the manner of the Bonne-\-ille embankments in Snake Valley, and include six distinct bars with a faint suggestion of fom- others. A profile of these is given in Fig. 3 of PI. XIV. Fig. 1 of tbe same plate exliibits the cut ten-ace with the underscore; Fig. 2, the double bay bar. In Tooele Valley tlie Provo presents the most remarkable expansion of a shore record that has anywhere been {)reserved. During that epoch the valley con tamed an ojieii bay receiAnng storm waves from tlie broadest por- tion of the lake. The principal excavation was from the alluvial slopes of 132 LAKE BONNEVILLE. the western base of the Oquiirh mountains, and the material was swept southward to the shaUow head of the bay, where it was built into a series of bars stretching from shore to shore with SAveeping curves. In this series 65 individual l)ars have been counted and their aggregate width is more than a mile. Their order of position is necessarily tlie order of their formation; and their profile (PI. XIV, Fig. 4) exhil>its in consecutive order the local variations of the relation of water to land during the Provo epoch. The double terraces, the double bay bars, the bar series of Terrace Mountain, and the bar series of Tooele Valley, constitute the wliole of our information with regard to the oscillations of the lake during the Provo epoch; and all effort to correlate them and deduce a consistent history has failed. In the discussion of the Bonneville profiles, it was found that the more extended series was represented in the less extended only by its highest members, the miniyia of the profiles disappearing as they were condensed. If the same relation subsi.sts between the Provo profiles, then each member of the Terrace Mountain series should be found to correspond to some max- immn of the Tooele Valley series. The comparison is necessarily begun by equating the highest member of one locality Avith the highest member of the otlier: — that is, by saying that the Terrace Mountain c and d are equivalent to the Tooele Valley C and D. Then a and h of the Terrace profile should be represented by maxima to the left of C in the Tooele profile; but the only maximum of this kind is at A, and is too low by nearly 30 feet. The ter- race from E to F may be compared without gi'eat incongruity with the bar e; but the maximum at H is 20 feet too high to be represented by the bar / Similar difficulties prevent the correlation of the Terrace profile with the double bar, Fig. 2; but they do not arise when the latter is compared with the Tooele profile. The higher biU' of the pair may fairly be taken as the equivalent of the Tooele group from A to F, and the lower bar may represent the embankments from G to I. The wave-cut terrace and underscore (Fig. 1) have no sjTnpathy with any bar groiip except the simjjle pair. It is probable that the greater and higher bar K was in Avhole or })art the contemporary of the terrace M ; and it is possible that the minor l)ar L was the contemporary of the underscore. Though the wave-cut ten-aces and the Tooele Valley bar series sever- PROBLEMS OF COKRELATION. 133 ally accord with the double bars, they do not harmonize ■with each other. Upon the assumption that each records the oscillations of the water-surface, the deduced liistories are different. The exceptional flatness and extreme breadth of the upper teirace seem to show that the waves were for a long time at a uniform horizon, or else that the latest work of excavation was at so low a level that all terraces of anterior production were undercut and obliterated ; the underscore appears to represent a brief lingeiing after the main terrace had been finally di-ied. The Tooele Valley profile, on the other hand, indicates a gradual rise of 40 feet from the base of the bar A to the upper ten'ace B, followed, first, by a tolerably uniform high stage BF, and, second, by a stage GI ten or fifteen feet lower. If the breadth of the bars be taken as a time scale, the liigher stage had twice the duration of the lower, but occupied somewhat less time than the gradual rise preceding it. If the production of an individual bar be taken as the unit for tune-scale, the higher stage had two and one-half times the duration of the succeeding low stage and tlu-ee times the duration of the antecedent rise. If, now, we correlate the central group of Tooele bars with the main wave-cut terrace, and correlate the outer group of bars with the imderscore, we find two diffi- culties. In the first place, the underscore represents but a small fraction of the period of wave action under consideration, while the outer series of Tooele bars, upon any plausible basis of estimate, represents a relatively large fraction. In the second place, the progressive rise implied by the Tooele profile has no expression hi the wave-cut terraces, where its eff"ect would be to impair the definition of the outer edge of the main terrace and contra- vene its characteristic flatness. There appears then no way in wliich to reconcile the vaiious analytic manifestations of the Provo shore on the hy- pothesis that the recorded oscillations are purely those of the water surface. The presumption is therefore in favor of the alternative h}'pothesis that there were difierential movements of the earth's crust within the basin dur- ing this epoch. Unfortunately, the data are too meager for the discussion of tliis hypothesis. 134 LAKE BONNEVILLE. THE MAP. During the prosecution of the field work, no attempt was made to ob- tain the data necessary for mapping the Provo shore-hne ; but the note- books contain so many incidental references to its position that it has been found possible to construct a map not gi'ossly en-oneous. Tlie reader is warned that the outline delineated in PI. XIII is approximate only. A similar qualification applies to estimates of area. The water surface at the Provo stage had an approximate extent of 13,000 square miles, 11,500 be- longing to the main body and 1,500 to the Sevier body. THE STANSBURY SHORE-IilNE. From the Provo water line to the margin of Great Salt Lake, the de- scent is more than 600 feet. From the same line to the Bonneville shore the ascent is less than 400 feet. In the upper sjiace all the conspicuous lacustrine features are referable to shore action, but there are subordinate evidences of sedimentation. In the lower space lake sediments predominate, gi-^nng their peculiar smoothness to the surface, and the shore tracings are relatively unimportant. Upon any profile a considerable number of shores can be recognized below the Provo; and it is probable that a. system of levelings would enable these to be con-elated in a consistent system. This has not been done, and only a single one has been widely recognized. Tliat one is distinguished merely by the gi-eater magnitude of its cliff's and em- bankments, but is not sufficiently accented to be everywhere identified. It is called the Stansbury shore-line. Its strongest delineation is upon Stans- bury Island, where owing to local conditions it rivals the Provo shore in definition and surpasses the Bonneville. In abundance of tufaceous deposit it probably ranks next to the Provo, Its height was measured at two points only. On the west side of the Terrace Range it lies 310 feet below the Provo shore; and at the north end of the Aqui Range 346 feet. At the latter locality it was found to be 330 feet above the level of Great Salt Lake. It is thus seen to di^ade about equally the interspace betwen the Provo shore and the shore of Great Salt Lake. At the tune of its formation the maximum depth of the lake was only about half as great as at the Provo date; and the water surface was corre- 5riCI-C0iCAL SUF.'vTY UiTSE B'.'S^EViLl.Z, PI J3! 013° 112 in' US* Ilr3i^> liy 0 Thtimjii-i MAP OF SIIOHK hMlJAXKMK.XTS. N'cai- (.ranlsxillc . I'la l!\ II A \Vh.-,.|i. SCALE c iflLl I //' /'rff f't'Tittinr^ \ \ . o5^ \'cv vx~ c-^ :.-$^-C-5i^" Kia I'l'ililc. A to It Vniical Sfilr litni iln Hfnu'rilal .lulhis Hicn & G>.lill) IlrsMli Kv li Ttu.n-jis STANSBtJRY SHORE-LINE. 135 spondingly diminished. The constructive waves were therefore less power- ful and the time necessary for the perfonnance of an equal work was longer. There is good e^•idence, however, that the period of time represented by this shore is shorter than that rejiresented by the Provo. The body of water covering the SeA-ier Desert during the Provo epoch was smaller than the body occupying the Great Salt Lake Desert at the Stansbury epoch ; and yet the shore phenomena by which it is outHned are upon a far larger scale than any exhibited by the Stansbury. The Avater whs at this time withdrawn from the Se^-ier Desert, but cov- ered the main portion of the Great Salt Lake Desert. It washed the foot of the "Wasatch and extended within a few miles of the western line of the Bonne^-ille shore, but was excluded from most of the bays at the north and south. Its total area was in the neighborhood of 7,000 square miles. THE INTERMEDIATE SHORE-TWINES. In every locality where the Bonne%-ille and Provo shores are marked by considerable acciunulations of shore di-ift, the whole of the intermediate slope is similarly characterized. In every locality where the Bonneville and Provo shores give eA-idence of excavation, the intervening space is com- pletely occupied by similar evidence, but the phenomena are in this case less conspicuous. DESCRIPTION OF EMBANKMENTS. Grantsviiie.-If thc rcadcr will turn to PI. XV, which represents a tract of country a few miles south of the town of Grantsville, he will see that an angle of the valley, containing a bay of the ancient lake, occasioned the local accumulation of large embaidi;ments. By studpng the contours of the map, or by referring to the accompanpng profile, he will see that these embankments have their crests at various levels, the order of heiffht beins also the order of horizontal position. The Provo embankment was carried entirely across the bay, so as to complete a bar; and the same is true of the one next to it in the series. The development of the other embankments was arrested while they were yet sjjits. Box Elder Creek, which was ti-ibu- 136 LAKE BONNEVILLE. tary to the bay, has its modem course deflected by the spits, and has opened a passage through the bay bars. Each of these embaidcmouts is the product of essentially the same combination of local conditions. At each of the represented stages the shore drift derived from a long alluvial slope at the north, beyond the field of the map, was earned southward toward the edge of the bay and there accumulated in a long embankment, built in the deep water of the bay on a line tangent to the shore at the north. Between tlie Bonneville and tlie Provo there are four principal embankments; and it was a natural assumption, made at an early stage of the investigation, that each of these embankments recorded the woi-k accomplished by the waves at a stage represented by the heiglit of its crest. This assumption was for a time unquestioned, but later developments led to doubt of its validity; and, in order to test it, a systematic collection of shore data was undertaken. Localities were sought where the configuration of the lake bottom favored the cousti-uction of shore embankments at all levels from the Bonneville to the Provo, and at such localities contour maps were made and profiles were measured with the spirit-level. By means of these maps and jirofiles, taken in connection with the details of structure observed at the same locality, the general history of the Intennediate shore-lines was developed, but the orig- inal assum])tion was overthrown. In order to present this history to the reader, with the evidence upon which it rests, it will be necessary to make him acquainted with a selected series of the maps, which series has been reproduced in the accompanying plates. Preuss vaiiey.-Pl. VIII rejiresents eight miles of the eastern side of Preuss Valley. At the right stand the rocky spurs of the Frisco Mountains, and against their base the stream di-ift from the canyons is piled in great alluvial cones. While the lake occupied the valley, the form of its shore was given by the contours of the alluvium, each great co7ie occasioning a rounded cape, and each interval between the cones, a bay, From three of the capes the cuiTcnts were deflected in such way as to accumulate the shore drift in a system of embankments, — and this at all levels from the Bonne^^lle to the Provo. Pis. XVI, XVII and XVIII show the details of the three localities of accumulation. •J S.C7E0L0GirAL SUPVET LAl-3 BCKNEMLLZ PLX\". MAP OF THE .NOKTll V,\{{)VV OF SHORE EMllAXKMEXTS IN J'ltKl'SS VALLEY, UTAH. Rv G K (Mlbert FEET JO' titt O'uloujs .-;//////. miii/'mr' ''In / / C ' ..-^'^-- Zn'Z^^^'^' VIEW AS SEEM FROM THE SOUTH Julius Bl«A Jt Co.lllh Drawn bv G Tlimri'" ■J .:\ 5L0LGorc.^ JUPVi-; -^ijyx E;.KNr.iLir PLr-rrr i -^-- va5>l .V ' ..' ' ■ ".-—2? N'^"'^' i "'""■^-" ! V \ ' ' i ^ S. , ] 1 " • " ■■ 1 MAP OF THE 1 1 MIDDLK ClJOrP 1 '"■■ i siiDPj-: i;MnA.\i\.\ii:.\ rs. 1 IN i'in:rss vai.i.kv. i'tak. 1 ' ..... .::o .... i ]0'/'rit (,>tltt'Utw IS.>nne\i7h' *- 1 ,- y *^^^^^ ^^^^^jlt^f^^Bm^ms^mf^^^ ' ^^" ■■' yiv y Pii'filr us .Mill /I, 'III //it Xi'ti/// ]'<'/tntil .s'iiih doiti'lr ih. Ilon/.i^ntdl IilUu- liifu .V Vu.h.h LAKE BOKKEVILLE FL^.TT 1 — rr ;/ » / ////;/// ' / .' ' / '■■ ,' ' ; / ■/ ' / \llilliii!ll''^/// \ I /|/ iiiiiim-'ii^^'''^^ / '/'\ //-'// MAP OF THE sonii (;];()r? OK SlIOKE EMBAXKMKNTS IN PREl'SS VALLKV, ITAll. l!v C; K (iillierl JCOC SCALE t--. - I- JO'fcft Cvntxuirt, Hon Ti e \ I i i tf •: Sif>f »MM^'^''* WMm PioiJie (IS seen iiwrn ihe South Ju]iua llicit ft Cu.Iitli llijwii Wl. Ti»..j,p^..i. EMBANKMENTS OF TOE INTERMEDIATE SHORE-LINES. 137 The snowpiow._A sliuilar compound embauknieut, but on a 'grander scale, was formed at tlie soutliem opening of the strait joining- the two principal bodies of the lake. Its general relations appear on PI. XXXI and its de- tails on PI. XIX. Tlie shore diift in tliis case came from the east, being derived from a great alluAnal slope fonned by the coalescence of many cones from the Sunpsou Mountains. The embankments into wliich it was built are characterized by the V-form, and are so piled one upon another as to have suggested the name Snowpluw, by which the group was distin- guished in the field notes. Stockton and weiisviue.-Tlie embaukments at Stockton (PL XX) are of a dif- ferent type, haA^ing been tlu'0\\Ti across a strait and not merely projected from a shore. That of the Boiine\'ille stage is, however, exceptional, run- ning athwart the others in the fonn of a broad spit ; and those of the Prove stage, wliich faU without the field of the map on the south side, are typical bay bars. A perspective view of the field of this maji is given in PI. IX, and a profile of the contiguous Provo bay bars in PI. XIV. The embank- ments at Wells^■ille in Cache Valley (PI. XXI) are of the same ijY>e as those near Grants^■ille, but are less perfectly preserved. A mountain stream flow- ing across them has 0]ieued a wide channel ; and the extremities of two em- bankments have been triuicated by land slides. Dove creek.-A gTOup of cmbaidiments near Dove Creek, represented in PI. XXII, is somewhat similar to the Snowplow, but the matei'ial was in large part torn hv tlie waves from solid rock, and not merely dug fi-om allu\-ium. It first traveled northward along the coast from which it was cut ; and then turning abruptly to the northwest, was built into ten-aces upon another face of the same island. COMPARISON OF EMBANKMENTS. For the pm-}iose of comparison, the vertical elements of all these local- ities have been assembled on a single page in PI. XXIII. The data are so diverse in character that they are not easily compared by means of profiles on a natural scale, and an attempt has therefore been made to eliminate all accessory features and represent merely altitudes and quantities of wave work. In each of the profiles of the plate, a straight line inclined at 45° is 138 LAKE BONNEVILLE. made to stand for the original surface upon wliich the embankments were built. The horizontal distance of each point of each profile from tliis base represents the total quantity of material added to the sliore at that locality and level. In the case of the Stockton diagram, Fig. 6, it was impossible to represent comparative quantities of material, and only altitudes are ex- pressed. At the north end of Preuss Valley the lower members were not mapped, because they lay at an inconvenient distance from the upper ; and the profile. Fig. 3, is therefore incomplete. The profile is additionally ex- ceptional in that it is doul)k'd, to represent two series of enibaiJcmcnts dif- fering in date of fonnation. The earlier series is drawn at the left, and the later, which in part overlies it, at the right. Fig. 5 represents a profile measured at Cup Butte, five miles northwest of the Snowplow. In this case the vertical element only is valuable for comparison, because the upper and ln\\er portions of the slope were not similarly disposed with reference to the waves. The lower received no deposit, but exhibits the i-ock of the liutte carved in terraces and cliff's. Fig. 10 represents the great embankment at the Point of the Mountain south of Salt Lake City. The vertical measurements for the profile in Fig. 7 were made by means of two mercurial barometers, one of which was read at short intervals at a station near by, while the other was carried from point to point. At Cup Butte, Fig. .5, the measurement was by means of a hand-level attached to a Jacob's staff", the unit of the instrument ha^^ng been determined experiment- ally by comparison with the sur\eyor's level. The remaining profiles were measured with a spirit-level. ' • The profiles are arranged upon the page in the order of geogi-aphic position. The tlu-ee groups in Preuss Valley fall within a radius of three miles. The Snowplow and Cup Butte groups are 100 miles farther north but are separated from each other by five miles only. The Grantsville and Stockton groups are' 10 miles apart and are 45 miles north of the Sno^^'l)low. The Wellsville and Dove Creek groups are isolated. They are 80 miles apart and each is 90 miles distant from Grantsville, the nearest of the other localities. The Point of the Mountain is separated from the Stockton group by an interval of more than 20 miles, including a mountain range. :.l MAP or Tin-; sxcm'i^i.ow, A CIJOITOK SlIOlli: TKiniACKS lira 1- llu- OLD HIVKH l!i:i), ITAH. i^^ tCAuE lli-teft Cuiili^in-^ ~%L^ MS. li»..:, A i'.,.i,.l. |lr.n«i. hy (i Thoinp^oi U S. GEOLOGICAL SUF.VET LAKE B01;KE\1LLE PL--3. V><_>-^ -p — .-» , ^■". — -. •■„!'- r-"'-:^., — ""?■ ;; \^~.:- <^v^^"f:._i..^:^~>-^:/p-;.y.':' .K-t_f'y -^ v>i-- ^■■•*^v "1 MAP OF THt PASS IMSllAM) TOOKI.l". VAIJ.I'YS, I'TAll slio-\vin^ tilt' M'AVK liriLT IJAHKIKII. Hv II A Whru-ler 5C*^L t 'jt> /«■/ /i.«^' J' :::^ Smt ot- jlncioit Channrl / itf'j'nixJ h'nsh i.'t^r VertitMl Sprtiim Ti-oni or U> iiu-^li Lnk<' Vrrln.it St II It tiuithlr- f/le //or I ^viU.tl Julu.M lli(-:i & Cu lilli Draf\>T. bi- C Tlnjinpiit *^f.^? S h «i I" ■• It n e MAP OF SlIOHK BARS ANDTlTvl^ACHS WKl.LSVIl.lj;. ITAll, r.v A 1. \\'.-l>slel- ~, ~^:3*>^ 1- J- i^~^ UI- I- i' t'net fontvttti, I --^Cn.:^,- - - Juliu.-< llu-» .\ i't. 1' VlEW FROM THE EAST '■■1'- '" II US. GEOLOGICAL SUPA1 LAKE B&NKEMLLE PL3XII \sr (';-■■'" l^J^^ 1 1 \i -BoTtnr\itlr >S/ityr,lin>- J'ru.u SI, or, I y MAP or SIIOHK TKlv'RArKS Nc;n- llovc ( rcrl<, rtrih Uv ((illirrl ■|'liuni|isnn >>.^'X\— -_ /(■' trrt Contours _^ ,^,. ^.., .-...w.w.v_-__„^__ , '\4-7-r^ Y r-N. J'ffM^ — ^— -'■ ,^.^ ,, . , t'.liu^ I;. en A r«.1.0, Drawn bvC. Tii..uip-... ATTEMPTS AT CORRELATION. 139 Having thus assembled the data, let us now endeavor to obtain a clear conception of the questions to be answered by their comparison. At the Grantsville locality the shore drift is built into a small mmiber of large, definite, individual embankments, diff"ering in height. The analogy of the Bonneville and Provo shores suggests the h}i3othesis that each of these em- bankments was produced by, and therefore represents, a prolonged mainte- nance of the water surface at a corresponding height. Under this hypothesis there should have been accumulated at each of the other localities during this time a corresponding embankment; and if all the embankments remain undisturbed in their original position, a complete correlation should readily be made out. For each of the principal embankments at Grantsville there should be found a representative at the same height in each of the other localities. If such coiTespondence is not found, it is necessary either to abandon the hj-pothesis, or else to supplement it by the assumption that the relations of the embankments were deranged by differential movements of the earth's crust occurring during the general period of their formation. Examining now another locality, as, for example, the "WellsAnlle, Fig. 8, we find that, although it exhibits a small number of large individual em- bankments, the altitudes of these do not correspond each to each with the altitudes of the Grantsville embankments. However the comparison is made this disparity appears. In the plate the Bonneville horizon is assumed as the common zero for the vertical elements of the profiles. This assumption is purely arbitrary, and was not adliered to in milking the comparisons. In order to test the matter fully, each group of embankments was represented on a sheet of transparent paper by a system of parallel lines whose intervals were drawn to a scale, so as to agree with the vertical intervals of the em- bankments.. These transparent sheets were then superposed in pairs and other combinations, and were tentatively adjusted in numerous ways, in the hope of discovering occult correspondences. Only one element of order was discovered. A horizon from 15 to 25 feet below the Bonne'ville (marked a on the plate) is discernible in eight of the ten localities. With this single exception, there are no correspondences which can not be referred to fortuitous coincidence. Not only is the series of altitudes different at each locality, but the number of embankments varies 140 LAKE BONKEYILLE. from place to place. It is evident, therefore, tliat the hj'-jiothesis of persistent water stages is tenable only with the addition of a hypothesis of contempo- raneous displacement; and the question arises whether we have any means of subjecting this phase of it to test. HYPOTHESIS OF DIFFERENTIAL DISPLACEMENT. The sup])lementary hypothesis is not a priori a violent one. As will be set forth in a following cliapter, our investigation has fully demonstrated that the Bonncvilh' sliore-line is no longer of equal altitude at all points, but varies within the region comprising these localities through a range of more than 100 feet. The same has been shown with reference to the Provo shore-line; and it has also been shown that a part of the Bonneville derangement oc- curred before the Provo epoch. In the series of localities represented by the profiles, the interval between the Bonne^^lle and Provo shore-lines ranges from 345 feet to 400 feet, exhibiting a difference of 55 feet. It is therefore easy to believe that the localities may have undergone relative displacement after tlie constniction of certain of the Interaaediate embankments and prior to the construction of others, or even that local changes of water level may have been thus occasioned at one locality while the process of shore forma- tion was continuous at another. The possibility of confusion thus intro- duced seems at first unlimited, and a rigorous test of the hypothesis would be difficult were it not for a fortunate circumstance. The surve}'ed locali- ties include several pairs, the members of which are so closely associated geographically that there is a strong presumjjtion against their having been affected discordantly by contemporaneous earth movements. The middle and southern localities of Preuss Valley, Figs. 1 and 2, are but two miles apnrt, and bear the same relation to the adjacent mountain range. The localities of the Old River Bed, Figs. 4 and 5, are five miles apart, and those of Tooele Valley, Figs. G and 7, about ten miles apart. The principal recent dis])lacements of the basin have been of the nature of broad, gentle undulations, not affecting the horizontality of the shore-lines, so far as that is distinguishable by the eye. The region including each grouj) of localities may properly be assumed to have risen or fallen in con- sequence of such earth movements without imj)ortant internal change; ATTEMPTS TO EXPLAIN DISCORDANCE. 141 and tliis circumstance leads us to anticipate tliat the members of each of these gi-ou])s of embankment locahties will be found to corresi:)ond with each other better than -with the members of other groups or with isolated locali- ties. This expectation is realized in the relation of the Bonne^'ille and Provo shores. In each of the two Preuss Valley localities the Bonneville-Provo interval is 345 feet. At the two localities of the Old River Bed it is 400 feet and 398 feet. At the two localities of Tooele Valley it is 375 feet and 378 feet. At the Point of the mountain, 20 miles east of Tooele Valley, it is 375 feet. When, however, the Intemiediate shores are considered, no cor- rplation is found. The harmonious relations exhibited by the Bonneville and Provo shore- lines at contiguous localities confirm the postulate that a general correlation should be possible in these localities, despite the influence of contempora- neous displacement, and ct)mpels us to reject dis2)lacement as a sufficient explanation of the discordance of the Intermediate shore-lines. By these considerations, and by others which it is unnecessary to de- tail, the writer was led to abandon the hypothesis of persistent water stages, even though a better was not immediately suggested. Eventually another was found, and this is believed to give a satisfactory explanation of tlie phe- nomena. It may be called the hypothesis of an oscillating Avater surface. HYPOTHESIS OF OSCILLATING WATER SURFACE. In order to set forth tliis hypothesis, it will be necessary to recur to the general theory of the construction of shore emljankments, page' 46, and imagine how the process would be modified by the contemporane- ous oscillation of the water surface. Let us select some point of the coast where the local conditions detennine the deposition of shore drift, and assume that a spit has been formed, its crest being slightly higher than the surface of the water when still. Suppose now that the height of the water surface is gradually increased, A portion or the whole of the shore di-ift contributed by the next stonn is deposited upon the top of the embankment, tending to restore the profile to its normal relation with the still- water level. During this restoration the growth of the end of the spit is retarded, or per- 142 LAKE BONNEVILLE. haps altogether checked. If the general rise of the water is very slow, the construction of the embankment keeps pace with it, and the crest maintains its nonnal height, but if the rise of water is more rapid, the spit is sooner or later submerged, so that the storm waves sweep over it. With a slight sub- mergence, the course of the shore current is unchanged, and the waves still break as they reach the line of the spit, so that the conditions of littoral transportation are not there abrogated. A portion of the force of the waves is expended on the land inside the spit, but the shore di-ift is not diverted or divided so long as the position of the shore cun-ent remains unchanged. The growth of the spit therefore continues in its submerged condition, and if the water level ceases to rise, the crest of the spit eventually emerges and acquires its normal height. As.sume now that the rise of the lake surface, being more rapid than the growth of the spit, does not cease, but continues indefinitely. A time must sooner or later be reached when the depth of water on the submerged spit pei-mits the waves to pass over it almost xmimpeded, and at the same time pei-mits the shore cun-ent to be deflected inward. The fonnation of a new spit then begins in a position higher on the sloping side of the basin. Now let the tendency of the water level be reversed, so that it gradu- ally falls. Additions will continue to be made to the new spit by the ac- cumulation of shore diift on its weather face and at its end ; but sooner or later the water will reach a stage at wliich the shore cuirent will be de- flected by the lower-lpng spit, and at which the waves in sweeping over that spit will be broken and diminished in force. Additions to the upper spit will then cease, and the growth of the lower spit will be renewed. If this theory is well founded, there should be produced at the margin of an oscillating lake a series of embankments separated by vertical inter- vals bearing some relation to the magnitude of the waves, and each of these should grow in height every time the oscillating water surface passes its horizon, either in ascending or in descending. The rate of growth would naturally be different at different points on the margin of the lake ; and the interval between embankments, being a function of wave magnitude, should vary in different regions, being gi-eatest where circmnstances are most favor- able for the development of waves. THEORY OF OSCILLATING WATER SURFACE. 143 This relation between the embankment interval and the local conditions affecting wave magnitude is' so cs^dent a .consequence of the theory that it may be used to test its applicability to the problem in question, and this may be further tested by considering the phenomena of littoral excavation in connection with those of littoral constmction. The conditions which theoretically produce a rhjiilmi in the process of littoral deposition have no similar effect upon the concomitant erosion. In the regions of littoral erosion, the shore currents are not deflected by circumstances associated with the rise and fall of the water level, and the zone subjected to the beatinjj of the waves bears alwavs the same relation to the still water level. An equable rise of the water should therefore pare away the coast in an equable manner; and upon the theory of rhythmic deposition, the Inter- mediate embankments should not be associated with sea-cliffs and cut- terraces of comparable magnitude. Proceeding now to the application of the Inqiothesis to the problem in question, we may premise that the water level has twice risen above the Provo horizon and afterward descended, one rise extending to the Bonne- ville shore-line and the other being nearly as gi-eat. The space occupied by the Intermediate embankments has thus been subjected to wave action at least four times. These oscillations have been demonstrated by independ- ent evidence; and it is probable that there were also niunerous minor oscil- lations. The conditions were therefore favorable for the production of the rhythmic result. The vertical interspaces between the Intermediate embankments yield e\'idence confirmatory of the hypothesis. Six of the localities represented in the profiles and maps are suitable for comparison. Among these the local conditions indicate the greatest waves at Grants\-ille and Dove Creek, and at these points the average interspaces between the principal embankments are 72 feet and 75 feet. The conditions are less favorable at Wellsville and the Snowplow, but it is doubtful wliich of these two localities should rank next At Wells^•ille the average interspace is 60 feet. At the Snowplow it is either 71 feet or 61 feet, according as an embankment of doubtful rank is included or excluded. In Preuss Valley, where there was comparatively small scope for the formation of waves, the average interspace is 53 feet. 144 LAKE BONNEVILLE. Equally harmnninus is the evldeuce from the phenomena of littoral excavation. Take, fur exajuple, the Snowplow. The material there aggre- gated was derived from a broad alluvial slo})e, partly represented in the northern portion of the map (PI. XIX). In this region there is a nearly continuous slope from the Provo terrace to the Bomieville terrace; and aboVe the Bonnevdlle cliff there is a continuous slope of undisturbed allu- vium. Tliis latter originally extended over the entire slope, including and beyond the ProA-o horizon, and it can be restored in imagination so as to realize the magnitude of the excavation. Fn)m ten to thirty fi'Ct appear to have been removed from the general surface, and this so evenly that there are only one or two points where the presence of sea-cliffs can be indicated ; and even these can not readily be traced to corresponding embankments. The same is tri;e in a genei'al way of all localities. Not only are the In- termediate embankments nowhere connected with a system of differentiated clifls and terraces, but it has been f lund impossible, (A\'herever the attemjjt has been made,) to trace their horizons fairly into the region of excavation. At the Snowplow locality, the excavated alluA'ium is of such nature as to be easily modified by the rain and it does not preserve the minor details of the configuration impressed on it by the waves; but elsewhere, on alluvial slopes of coarser material, the interspace between the Bonneville and Provo cut-ten-aces has been observed to be occupied by a continuous sy.stem of naiTow terraces and clifl's, constituting a sort of horizontal striation of the sui-fiice. At one point, near Pilot Peak, thirty-tln-ee separate terraces were counted, the average interspace being less than ten feet. The hypothesis receives additional support from the structure of the individual embankments. The spit built by the waves of a lake with a con- stant level should nonnally have a certain simplicity of structure, the prin- cipal additions to its mass being made at the distal end, and the deposits near the crest liaA-ing no irregularity, except that referable to the disparity, in force and direction, of the constructive storms. A sjiit constructed by the waves of an oscillating water surface should theoretically be begun at a relatively low level and receive additions in the form of superposed spits of various altitudes and lengths, some extending to the end of the mole and others stopping short. The compound structure is characteristic of the ACCESSORY EVIDENCE. 145 Intermediate embankments. Sectional exposures are indeed rarely to be seen; but from many of the embankments there project, either at the distal extremity or on the shoreward side, shelves or sjiurs indicating the horizons of the lower Avave work and testif}*ing' to the composite structure of the mass. Fig. 25 gives an illustration of this, observed near Willow Spring, west (if the Great Salt Lake Desert. A broad spit is diaracterlzed J^y a hook at its extremity. A study of its details shows that the shore diift, under the m Fig. 25. — Coiopouod Hook of an lutermediate Shore-line near Willow Spring. Great Salt Lake Desert. influence of the dominant waves, here from the north and northeast, traveled from a to h. By less powerful Avaves from the east and south it was then carried about the end of the embanlcment to the recur-ved point c, a point with a peculiar and notal)le outline. On the lee side of the spit, at a point where the waves could have no force after its construction, there are tlu-ee projecting tongues d, c, f, built of beach-rolled gravel and closely resembling the extremity of the point c. The highest is twenty feet below the spit; the others thirty and forty feet. They are eA-idently more ancient hooks, the MON I 10 146 LAKE BONNEVILLE. ai:)pendages of similar but shorter and \owev spits, which may fitly be re- garded as progressive stages of the huge table ultimately constructed. Finall}-, the siugle element of order detected in the accumulated pro- files is by this hypothesis shown to be consistent with the general want of order. The teiTace («, I'l. XXIII) lying from 15 to 25 feet below the high- est Bonnevilie embankment, was preserved because it was the penultimate deposit of the ascending series, and because the ultimate deposit was too meager to mask it. The differentiated series of Bonneville bars described in a ])receding section shows that the penultimate water stage was about 20 feet below the ultimate. Wherever the penultimate contriljution to an em- bankment was made u})on its lakeward face, it escajjcd concealment by the final contribution, which was small in amount and was ])erched upon the to]) of the same embankment. The second hypothesis is thus sustained at all points. The Intermedi- ate embankments record the wave action of an oscillating water surface. "Within this zone the water level did not long linger at any one horizon, or if it did, the record of that lingering Avas effaced by later action. It follows as a corollary from this discussion that cut-terraces with their associated sea-cliffs afford a more trustworthy record of persistent water .stages than do embankments. It is an additional mark of persistent stages that the}- afford coordinated terraces and embankments. It is important to note, however, that neither the sea-cliff nor the cut terrace, if observed alone, affords satisfactory evidence of persistent wave action at one horizon. They must be found together. A slowly rising tide continually abandons the freshly cut terrace and attacks with its waves the freshly cut cliff above it. In this way a cliff is carried before the ad- vancinc water of an t)scillatin"' lake ; and when the maxinuun is reached and reces.sion follows, the cliff is stranded, so to speak, at the upper limit, e%en though the water margin Avas retained there a short time only. Sim- ilarly, it is conceivable that a falling lake surface may carry before it a cut terrace without leaving at any horizon a sea-cliff of comparable magnitude. The first of these conclusions has an application in the case of the Bonne- ville shore-line, which, as already remarked, .is characterized by the great lieifht of its sea-cliffs, but is inferior to the Provo shore-line in the width CIlAIiACTEKS GIVEN BY STABLE WATEK LEVEL. 147 of its cut teiTaces. The considerations here adduced serve to complement the partial explanation of this contrast advanced on page 129. As already intimated, the coniijilation of the Intermediate embankments was the result of a series of oscillations of the ancient lake, Avhereby a zone of wave action was carried alternately upward and downward over the slope. The basis for this statement does not lie in the embankments them- selves so nuich as in tlie associated lacustrine and alluvial deposits. It is unquestionalily true tliat the entire history of oscillatiim is embodied in the internal sti'uctures of tlie einl)ankments, Ixit these are not exposed for exam- ination, and the external forms aft'ord information for the most part only of tlie latest additions. It is a curious fact that those forms of embankments appear to have l)een moulded by a gradually rising rather than by a falling tide. The last general movement of the Avater A\'as of com'se a recession, for the slopes are noAv dry, but that recession has left so little trace above the Provo horizon that we are led to believe it was far more rapid than the j)receding advance. This conclusion is as interesting as it was unexpected ; and it is proper that the e%adence on which it rests be presented somewhat fully, especially as it has been assumed by several investigators, including myself, that the several shore marks of the series represent lingerings of the ancient lake dimng a gradual recession. SUPERPOSITION OF EMBANKIIENTS. The snowpiow.- In the first place, there are many superficial indications of the overlapping of low embankments by high ones. If the reader will turn to the map of the Snowplow (PI. XIX), he will see that the table lettered a is not entirely sup})orted by the taljle h, but jn-ojects a little on the south side so as to rest partly upon the general slope which is the connnou founda- tion of both. (It is necessary to restore in imagination tlie contours inter- rupted by the di-ainage line southeast of the letter a and dividing the embankment it indicates.) As has already been explained, the material of the Snowplow was derived from the region fff, and was di-ifted along the shore from southeast to northwest. That wliich composes the upper surface of each embankment must have been can-ied along the southera edge of the 148 LAKE BO:N^;EVlLLE. Snowjilow by beach action, so that each embankment was, at the time of its completion, connected by a continuous beach with the source of supply. Tlie embankment h is not so comaected, for the eA-ident reason that its southern edge has been overlapped by the latest addition to embankment a. If the waves during the recession of the water had made a contribution to the lower embankment, they must either have excavated the side of the upper embank- ment or else have built a platform around it, and in either case the slope from the crest of the upper to the foundation plain would not have the observed uniformity and steepness. A similar relation of parts shows that the em- bankment h was com])]et(d nftcr the embankment c, so that at least three of the members of the series received their final moulding- in ascending order. Reservoir Butte.-At Reseiwolr Butte substantially the same story is told, but in different language. The face of the butte turned toward the open lake was rugged in the extreme, and the configuration of the neighboring bot- tom was irregular, so that, as the depth of the Avater changed, the conditions determining the transfer of .shore diift and the cqnstruction of embankments were continually modified. The resulting embankments were not built into a svnunetric system but Avere thrown together in an irregular and unique group. By referring to Pis. XXIV and XXV, where they are represented l)v vertical and horizontal sketches,^ it will be seen that, of those above the Provo, the highest is the last formed, overlapping all the othor.s. Number 2 (thev are numbered in the order of height) has no visible connection by beach with the north or weather fiice of the butte, whence its material was deriAeil; and its form and relations show that it could not have been con- structed after the completion of Number 1. The third and ])art of the fourtli are in a similar manner overplaced by the second, and were evidently earlier formed. The fourth is however .separable into two parts, A\liicli may have been formed at different times; and the outer, marked 4« in the diagram, is not so related to No. 2 as to demonstrate the order of sequence. It is however ovei^ilaced bv No. 1. The relative age of the third and fourth is not a])par- ent; but the fifth, which lie^ in a bay completely sheltered by the fourth, is evidently of gi-eater age. The sixth and eighth have no detemiined relation • Tbo plat of these erabanliments given in PI. XXV cannot claim the accuracy of other maps of embankinenta. It was sketched in the field without the aid of instruments, and may be very inaccu- rate in matters nnessential to the discussion above. -J .1 ■ m.^: \ \ I \ V \s^^ \ jAWWilii w rf \^ mi'"% ^|!P■»'^ ■ f^:v^v^ - > ?^ — 5 ^ ^ r ^' b ^ '-/^ - ^ -r- fz -■ /\l ^^:. \ \ 'S(?fh^ \C \ ] SUPERPOSITION OF EMBANKMENTS. 149 to any other except the first, which the}' iiiiderhe; an J the seventli, -vvliich projects from beneath the fourth, shows no direct relation with any other. The ninth is the Provo, and this proclaims its recency by its relation to tlie first. Its table extends to the north face of the butte, and not merely passes the face of the first or Bonneville embankment but is in part carved from it. The Provo waves encroached also upon the eighth embankment. These relations may be tabulated in the following form, in which the word "ante^^ sliould be construed to mean comjileted at an earlier date than. ^ S.inte2 & ante 4 > ante 4a Ji' ■ ante 1 ante 9 stockton.-Another unique aggregate of embankments is equally instruct- ive. PreA-ious to the rise of the lake, the di-ainage of Rush Valley was tribu- tary to that of Tooele Valley, the connecting parts haA-ing a continuous descent from south to north, and an ample channel, of which a portion is yet clearly to be seen. At the point of greatest constriction between the two valleys, where the Bonne\-ille strait had a width of only 8,000 feet, the bot- tom of the channel ran about 350 feet below the level afterward marked by the BonneA-ille shore. At all high stages of the lake the strait received a large quantity of shore diift from the northeast, and a series of curved bars were thromi across it. These bars have a total width of 5,000 feet, and partially overlap each other, so as to constitute a single earthwork of colossal propor- tions. Whenever the Avater surface fell below the highest completed Ijar, the Rush Valley bay was completely severed from the main body, and became a lake by itself This lake Avas so small that its waves were comparatively powerless; and, although traces of their work can be discovered, they did not materially influence the configuration of the earthwork. The locality is exhibited in the foreground of the view in PI. IX and in the map and pro- file of PI. XX. If the reader Avill refer to the latter plate and give attention to the profile in connection with the map, he Avill see that the bars rise in consecutiA-e order from a to g, and that each has a curved axis Avith concaA-ity toward the north. This curvature, Avhich is characteristic of bay bars in gen- 150 LAKE BONNEVILLE. eral, shows that the waves concerned iu their production came from the north. It is evident that after the bar b was constructed, the bar a was protected from all further wave action, a was therefore completed before h was built; and in general the order of construction could not have been other than the order of the letters, — the lowest bar a being the first, and the highest bar g, the last. The order of construction was therefore from low to high. It is to be noted that this order is demonstrated only for the visible or superficial portiiins of tin- earthwork. There may be beneath the bar//, for example, a dee})ly buried series of bars lower than a, and either younger or older; and so of any other of the higher bars. We have no reason to believe that the whole history is embodied in the ^•isible phenomena. The bar ff diff"ers from the others in that it is not uniform in height throughout its length. The lowest point of its crest is approximately in the position occupied b}- the letter; and from this there is an ascent of about 30 feet toward either shore. At the Bonneville stage the strait was not closed by a liar, but the shore drift was l)uilt into spits. That at the west is short and has the form of a hook. It is crested from end to end by a slender ridge, built at the culminating water stage. The eastern is straight and broad and 6,000 feet in length. Its proximal end bears two small spits, referable to the culminating stage of the water; and its distal end e-vidently overlaps the lower members of the compound earthwork. So fiir as outward appearance goes, this is purely the product of shore action at the Bonneville stage; but it is possible that similar spits were formed at lower stages, so as to consti- tute a foundation for the Bonneville spit. One of the most striking features of the series of bars is the paucity of wave marks upon the northern face. There is a diminuti\'e bar, character- ized by an abundance of tufa, imposed on the face of the gi-eat bar g four feet below its crest ; and twelve feet lower a wave-cut teirace is barely per- ceptible. These may record an oscillation of the water after the comple- tion of the great bar and before it rose to the Bonneville shore ; or they may have been produced by the receding water after the highest level had been touched. In any event, the final recession must have brought every foot of the northern slope of the earthwork within reach of the waves, and SEQUENCE OF BARS AT STOCKTOX. 151 the sun'i^■ing continuity of the slope testifies to tlie rapidity of the reces- sion. The conditions for wave work were unchanged. The alluvial .slopes which had furnished the gravel for the several embankments, still ofi'ered an inexhaustible supply, and the same cuiTcnt* and waves must have been set in motion by the storm winds ; l)ut the lake seems not to have tamed long enough at any one level to add a terrace to the structure. Another e\"idence of the rapidity of the final descent of tlie waters is found in the failure of the waves at any of the Intermediate horizons to un- dercut the embankments constructed at the higher stages. If the water tarries long at one level, the changes it effects in the form of the shore finally modif\" the currents so as to shift slowly the districts of erosion and of construction. Spots that were at first excavated are afterward made to receive dei)osits, antl portions of the original deposit are afterward rem(i\ed. Instances are known in which llie Provo waves have pushed tlieir excava- tion to the heart of the Intermediate embankments, so as to undercut even the highest members ; and there are few localities of great wave action ^\ hich do not exhibit more or less encroadunent ; but there is no evidence that the waves of any Intermediate stage have seriously impaired any higher embankment. There is a narrow wave-cut teiTace on the north face of the Stockton earthwork; two lines ixve engraved on the points of Intennediate terraces in the Snowplow; and there is possibly a similar occurrence in Preuss Valley ; Init no locality gives evidence of long-continued action. Blacksmith Fork—Thc undcrcuttiug of the Provo shore has in two jilaces exposed instructive sections of the Intermediate embankments. At the south end of Cache Valley, close to the point where l^lacksmith Fork issues from the niountain, there is a section, nearly 300 feet in height, show- ing a face of clean gravel, which has slidden down so as to coAer the entire surface — if, indeed, it does not constitute the entire mass. At four horizons this is barred across by level lines of cemented gravel marking successive positions of the upper sui-fiice of the mass as it was piled. Dove Creek.- A siuiiLir escai-jimeut of gravel is exposed on the south face of the Dove Creek group of embankments (see profile diagi-am on PI. XXIL), and a similar series of parallel lines can be traced across it. They are best seen from a distance, and on close examination jirove to consist 152 LAKE BONNEVILLE. merely of a scattering growth of bushes. There is no visible v