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Department of the Interior

Hubert Work, Secretary

U. S. GEOLOGICAL SURVEY
George Otis Smith, Director

Bulletin 760-D

PEDESTAL ROCKS IN STREAM CHANNELS

BY

KIRK BRYAN

Contributions to the geography of the United States, 1923-1924

(Pages 123-128)

Published AprU, 1925

WASHINGTON

GOVERNMENT rillNTING OFFICE
1925

\

CONTENTS.

Page.

Introduction 123

Devils Top and similar rocks near Spokane, Wash 124

Rock in Owens River, Calif 126

Rock in Yellowstone National Park 127

Conclusions 127

ILLUSTKATIONS.

Page.
PiATE XXXI. A, Devils Top, Deep Creek canyon, 8 miles northwest of
• Spokane, Wash. ; B, Incipient pedestal rock, Colum-
bia River below China Bar, 9 miles downstream from

junction of Spokane River, Wash 12G

XXXII. A, Pedestal rock in Owens River, Inyo County, Calif. ;
B, Pedestal rock in Gibbon River at Chocolate Cas-
cade, Yellowstone Park, Wyo 127

n

PEDESTAL ROCKS IN STREAM CHANNELS.

By Kirk Brtan.

INTRODUCTION.

Isolated masses of rock, especially those of unusual shapes, excite
much interest and are commonly regarded with some little awe — a
relic, perhaps, of those feelings and impulses which caused the erec-
tion of the great stones of the Druid monuments. The fanciful or
mythical names that are almost spontaneously applied to such rocks
testify to this popular interest, but the origin of these masses has
received only scant notice by scientific men. This attitude is no
doubt justifiable on the ground that there are more important mat-
ters for study. However, the type of isolated rock consisting of a
larger mass above supported on a more slender pedestal has been
used as a criterion in the study of larger problems. Such pedestal
rocks have been cited as a measure of weathering since glaciation^
and also as proof that an area was not covered by continental ice.-
That pedestal rocks may be formed by the sand-blast action of winds
seems probable, but that such rocks in arid regions are necessarily
proof of wind scour has been denied in a previous publication,^ in
which a fairly complete list of papers on the affirmative of this
question may be found.

The object of this paper is to call attention to some examples of
pedestal rocks of well-developed form that stand in stream channels
and are produced by a process which bears no causal relation to wind
erosion, yet that, if found in some other environment, might easily be
confused with pedestal rocks resulting from wind scour.

Two of the examples cited have not been seen by me. One is de-
scribed from a photograph and notes by Willard D. Johnson, whose
untimely death cut short the career of a keen observer much inter-
ested in the minutiae of erosive processes. The other was called to
my attention by my friend and colleague, H. T. Stearns, who has al-
lowed me to use his photograph and notes. William Donahue, of
Spokane, furnished the photograph of the Devils Top.

1 Huglies, T. M., On some perched blocks and associated phenomena : Geol. See. London
Quart. Jour., vol. 43, pp. 522-539, 1886.

^ AJden, W. C, The Quaternary geology of soutlieastei'n Wisconsin : U. S. Geol. Survey
Prof. Paper 106, p. 41, pi. 16, A, 1918.

3 Bryan, Kirk, Pedestal rocks in the arid Southwest : U. S. Geol. Survey Bull. 760, pp.
1-11, 1923 (Bull. 760-A).

14242°— 25 123

124 CONTRIBUTIONS TO GEOGRAPHY OF UNITED STATES, 1923-1924.

DEVILS TOP AND SIMILAR ROCKS NEAR SPOKANE,

WASH.

Spokane, Wash., lies at the eastern margin of the Columbia
Plateau, which terminates here in black cliffs and crags of basalt that
front on the broad valleys of Spokane and Little Spokane rivers.
In these valleys stand outlying portions of the plateau bounded by
similar cliffs. Spokane River within the citj'^ plunges over ledges
of basalt in Spokane Falls and about 7 miles below the city enters
the long canyon that forms the northeastern boundary of the Co-
lumbia Plateau. The basalt flows that form the top of the plateau,
known as the " rim rock " flows, have an altitude of about 2,400 feet.
The flows that crop out in the bed of Spokane River and in the im-
mediately adjacent cliffs are a younger series that attain an altitude
only slightly above 2,100 feet. They lie within ancient valleys
eroded in the plateau. These valley flows, though younger than
the flows of the plateau, are thought to belong to the same general
period of volcanism, in Tertiary time.* The lavas of this series, at
least in the immediate vicinity of Spokane, do not have the columnar
jointing normal to basalts but are divided into great blocks by widely
spaced joints. In consequence they yield on erosion large masses,
many of which have peculiarly striking forms. Some of the most
interesting of these masses are to be found in the canyon traversed
by the lower course of Deep Creek, a stream that rises on the plateau
and flows northeastward about 15 miles to Spokane River, which it
enters 8 miles below Spokane. The stream plunges over the "rim
rock" basalt and has cut a deep and narrow gorge in the younger
basalt flows, which form a shelf along Spokane River. The lower
part of the canyon is at one place only about 50 feet wide, and here
is the Devils Top, one of a number of blocks that have fallen from
the cliffs above. As shown in Plate XXXI, A, this block tapers
from a rounded top to a narrow base. The rock would fall but for
the fact that it rests against the side wall. It is nearly circular in
plan and about 30 feet in greatest diameter. It is about 28 feet high
and the tapering base is about 3 feet in diameter where it rests on the
bedrock of the stream channel.

The rounded form of the upper part of the Devils Top is a char-
acteristic weathering form of the basalt of this locality, and similar
rounded domes cap the cliffs from which this block has undoubtedly
fallen. The minutely and irregularly fractured surface is also
characteristic and may be ascribed with some assurance to frost
action. Only in shape does the rock differ from adjacent blocks.

* Pardee, J. T., and Bryan, Kirk, Geology of the Latah formation in relation to the
lavas of the Columbia Plateau near Spokane, Wash. : U. S. Geol. Survey Prof. Paper
140-A (in press).

PEDESTAL ROCKS IN" STREAM CHANNELS. 125

The undercut sides seem, however, to be due to the erosive work of
the stream. Deep Creek has strong freshets each spring, and during
these freshets the velocity of the water around the rock must be high,
because of the reduction in the width of the channel. The driftwood
on the top of the rock, plainly visible in Plate XXXI, A, shows that
the rock is at times overtopped by the stream, but the actios of the
stream is more prolonged and effective on the lower part of the
rock. Here the force of the moving water, with its contained debris,
removes the small blocks already loosened by frost, and perhaps
the freezing of the water m winter facilitates such loosening. That
direct scour does not seem to take much of a part in this process is
shown by the lack of polished surfaces.

Undercutting by streams is hardly a common phenomenon in
this region, and there are cliffs and individual rocks along Spokane
Kiver and elsewhere in the region that are not notched. On the left
bank of Columbia River below China Bar, however, there are a group
of rocks of which some are loose blocks and others are portions of
a lava flow isolated by weathering along widely spaced joints. The
lava is part of the great series underlying the Columbia Plateau
but resembles in its lack of columnar joints and method of weather-
ing the flows on Deep Creek, which are doubtless somewhat younger.
Some of these blocks have vertical walls, and others are notched
near low-water level. The rock shown in Plate XXXI, B, ap-
proaches the form of a pedestal rock. The minutely and irregularly
fractured surfaces of the block indicates weathering by mechanical
forces, but examination of the interior of these fractured pieces
shows that there has also been some chemical action. Apparently the
effect of the river water is to speed up mechanical erosion and re-
move partly weathered fragments. Doubtless the undercutting
would be more marked if the river held a nearly constant level, so
that its action affected only a small zone. But Columbia River is
subject to a prolonged annual rise of 30 to 40 feet. The maximmn
estimated discharge of the river at Wenatchee and Vernita, the
nearest stations downstream, was 710,000 second-feet, on June 7,
1894, and the minimum discharge 23,900 second- feet, on January 31,
1917.^ During such floods the water doubtless has the same effect on
all parts of the rock. In the rise and fall also the surface of the
water occupies every position on the rock. Xot only do these condi-
tions tend to diminish the relative intensity of the notching action,
but it is obvious that on a river subject to such floods pedestal rocks
with slender pedestals would be snapped off, and there is thus a
limit to the development of such forms.

s Paxker, G. L., and Lee, Lasley, Summary of hydrometric data iu Washington, 1878-
1919': U. S. Geol. Survey Water-Supply Paper 492, p. 118, 1923.

126 CONTEIBUTIONS TO GEOGRAPHY OP UNITED STATES, 1923-1924. ^

ROCK IN OWENS RIVER, CALIF.

The photograph reproduced in Plate XXXII, A, was taken by
Willard D. Johnson in the canyon of Owens River, Inyo County,
Calif. According to his notes the locality is "just above the junc-
tion of Burcham Canyon and ' The Bridge ' " ; the rock is rhyolite
of the*" exfoliating type " found thereabouts and contrasting with
a neighboring type which yields to weathering largely by solution.
Johnson records also that the boftlder is said to have developed the
neck or pedestal in the 20 years that it had been under observation
by ranchmen in the neighborhood.

At this point Owens River runs in a deep canyon and, as indi-
catSd in Plate XXXII, A, is swift and turbulent. However, as
shown by the records of the United States Geological Survey gaging
station near Round Valley, just above the junction of Rock Creek,
at the lower end of the canyon, the flow of the stream is relatively
steady. The yearly mean discharge has ranged from 181 to 380
second-feet. The maximum recorded discharge of 1,190 second-feet
occurred in June, 1907, and the minimum of 100 second-feet in Feb-
ruary, 1919. Evidently the ordinary flow, fluctuating over a nar-
row range, has eroded the neck of the rock, and the flood flows are
not severe enough to break it off, *

The region has an arid climate and might even be called a desert.
The river in the canyon descends from an altitude of 6,700 feet to
4,400 feet, and the climatic conditions are similar to those at the
nearest towns, Bishop and Laws, which have an altitude of about
4,100 feet. The 16-year rainfall record at Bishop, as compiled by
Lee,^ shows an annual mean of 5.61 inches, and the 14-year record
at Laws, 4.40 inches. Even if allowance is made for an increased
rainfall in the locality of the pedestal rock on account of its greater
altitude, it may still be considered in an arid region.

Though the statement of the local ranchers recorded by Johnson
that the shape of the rock was developed in 20 years can hardly be
true, it is evident from the photograph that stream, abrasion operat-
ing against the surface of a rock already divided into small flakes
by exfoliation has produced the notch that forms the neck. The
neck is excentric, and the greater overhang on the upstream side
may be due to greater wear on that side. The rock appears also to
have been slightly polished by the water and its contained sus-
pended matter.

* Lee, C. H., An intensive study of the water resources of a part of Owens Valley,
Calif. : U. S. Geol. Survey Water-Supply Paper 294, p. 91, 1912.

/

U. S. GEOLOGICAL SURVEY

BULLETIN 760 PLATE XXXI

A. DEVILS TOP, DEEP CREEK CANYON, 8 MILES NORTHWEST OF
SPOKANE, WASH.

B. INCIPIENT PEDESTAL ROCK, COLUMBIA RIVER BELOW CHINA BAR,
9 MILES DOWNSTREAM FROM JUNCTION OF SPOKANE RIVER, WASH.

U. S. GEOLOGICAL SURVEY

BULLETIN 760 PLATE XXXII

A. PEDESTAL ROCK IN OWENS niVER, INYO COUNTY, CALIF.

B. PEDESTAL ROCK IN GIBBON RIVER AT CHOCOLATE CASCADE, YELLOW-
STONE PARK, WYO.

PEDESTAL EOCKS IlsT STEEAM CHANISrELS. 127

ROCK IN YELLOWSTONE NATIONAL PARK.

The pedestal rock illustrated, in Plate XXXII, B^ is one of the
features of Chocolate Cascade, a small rapid in Gibbon Eiver 3
miles southwest of the well-known Norris Basin, in Yellowstone Na-
tional Park. According to H. T. Stearns, who visited the locality
in 1923, the rock is composed of rhyolite. As is evident from the
photograph, it is a remnant of a ledge, and the notched rock, or
incipient pedestal rock, on the right, once belonged to the same
ledge. Doubtless at one time there was at this place a considerable
fall. The stream has eroded the ledge in such a way as to leave
remnants which, though obstructing the flow, were strong enough
to resist being carried entirely away.

Gibbon Eiver at the United States Geological Survey gaging sta-
tion 4 miles above its mouth has a drainage basin of only 117 square
miles and a minimum recorded discharge of 62 second-feet. No
gagings have been made at high water, but the maximum discharge
is probably not much over four times this amount. The incomplete
record indicates that the stream has a relatively steady flow, such as
might be expected of a stream rising in well-wooded mountains and
having a number of meadows and swamps along its course.

On account of prevailing low temperatures the climate of the area
is relatively humid, although the mean annual precipitation shown by
a 32-year record at the Weather Bureau station at Yellowstone is
only 18.70 inches. Much of this precipitation falls as snow, and
the result is that the vegetation and most of the erosional features
of the area are those of a humid country.

CONCLUSIONS.

The rocks described in the foregoing paragraphs are, so far as
form alone is concerned, typical " mushroom " or pedestal rocks.
They are composed of material of almost equal hardness from base
to top and have attained their form as the result of differential
scour rather than differential weathering. Thus they differ in com-
position and origin from the pedestal rocks described in a previous
publication.'^

Save for the fact that these rocks occur in stream beds, they might
be mistaken for rocks formed by wind scour. It is also entirely
possible that rocks in arid regions formed by stream scour may have
been mistaken for rocks formed by wind scour. Such confusion is
the more likely in that the areas in which the examples cited in this
paper occur have no great similarity in climate. Eastern Washing-
ton, in which the Devils Top and the rock in Columbia River were
formed, has a subhumid or semiarid climate, typified by that of

'' Bryan, Kirk, op. cit.

128 COlNTTMBUTIOlSrS TO GEOGRAPHY OF UNITED STATES, 1923-1924.

Spokane, which has a mean annual precipitation of 18.85 inches and
a cold winter. The Owens River canyon lies in a warm arid region
with an annual rainfall of only a little more than 5 inches. Yellow-
stone Park, on the other hand, has a cold humid climate. The char-
acter of the stream flow and the original form, position, and physical
characteristics of the rocks are probably more influential than
climate in producing these remarkable forms.

Note. — The rock in Gibbon River, Yellowstone Park, has also been described
by E. A. Martel, who visited the locality with the International Congress of
Geographers in 1912. His note, illustrated with three excellent photographs,
was published in the Comptes Rendus des Seances de I'Academie des Sciences
de Paris, vol. 159, pp. 87-89, 1914. Martel has also described a large number
of pedestal rocks in other localities, which he attributes to the action of both
surface and undergi-ound streams.

INDEX

A Page

Alden, William C, The physical features of

central Massachusetts 13-105

Analyses of waters from Pecos Valley, N.

Mex_- 120

Arizona, southern, pedestal rocks in 7-10

"Auburn River," Mass., course of, in Ter-
tiary time ... 22-23,27

B

Barre Falls, Mass., plate showing 105

Blackstone VaUey, Mass., Tertiary streams

in 22,27

Blocks with vertical bedding planes, erosion

of 5

Bottomset beds of sand plain near Clinton,

Mass., plate showing 70

Boulders, glacial, in central Massachusetts.. 58-59
glacial, in central Massachusetts, plates

showing 58

of erosion, plate showing 4

perched, plate showing 58

Brimfield, Mass., glacial lake near 77-78

Brookfield, Mass., glacial lake at 78-79

Bryan, Kirk, Pedestal rocks in stream chan-
nels 123-128

Pedestal rocks in the arid Southwest 1-11

C

Calhoun, F. H., cited 36-37

Carlsbad Cavern, N. Mex., characteristic

scene in, plate showing 112

description of 109-113

entrance to, plate showing 112

Hattin's Dome and the Temple of the

Sun in, plate showing 112

partition of onyx in, plate showing 112

piUars of onyx in, plate showing. 112

spring deposits in, plate showing 112

stalactites in, plate showing 112

stalagmites and column in, plate showing. 112

Twin Domes in, plate showing 112

Yeitso's Pillar in, plate showing 112

Cavernous condition in rocks, possible depth

of 113

Caverns in rocks, drainage through 116-117

Clay, laminated and crumpled, plates show-
ing.... 38, 71

Clinton, Mass., glacial deposits near 65-72

Columbia River, Wash., incipient pedestal

rock on, plate showing 126

weathered rocks on... 125

Connecticut Valley, glacial lakes in, history

of... 89-92

glacial lobe in, history of. 87-89

Crosby, W. O., cited 24,66,68-69

D Page

Dana diorite, plate showing 17

Debris, falling of, into caverns 117-119

Devils Top, in Deep Creek, Wash., descrip-
tion of. 124-125

plate showing 126

Drift, glacial, nature of 29-31

Drip furrow below pedestal rock, plate show-
ing 4

Drumlins in central Massachusetts 40-43

plate showing 38

Emerson, B. K., cited 27-28,29,89-90,91-92

Esker, plate showing 38

Eskers in central Massachusetts 50-54

origin of 54

Flood plain, plate showing 58

"Flowstone, " definition of ._ 110

Foreset beds of sand plain near Clinton,

Mass., plate showing... 70

G
Glaciation, effects of, on rock at Clinton,

Mass., plate showing 31

effects of, on rock in Greenland, plate

showing 30

stages of 32-33

Gregory, H. E., cited 1

Gypsum, sink holes dissolved in 114-116

Ice, glacial, thickness of... 36-37

Kame terraces in central Massachusetts 49-50

origin of 47-49

Eettleholes, origin of 68-69

plate showing 70

Lacustrine clay, deposit of, in central Massa-
chusetts... 37-38

Lake Assabet, glacial, Mass., history of 74-75

Lake Nashua, glacial, Mass., Ayer stage of.. 72-73

glacial, Mass., Boylston stage of 61-65

Clinton stage of 65-72

map illustrating relations of ice front

to 70

Quinapoxet stage of 60-61

Lake Quaboag, glacial, Mass., history of 79-81

Lakes, glacial, origin of 59-60

Lancaster, Mass., glacial deposits near 73

Lee, Willis T., Erosion by solution and fill. 107-121

129

130

INDEX

Page

Lees Ferry, Ariz., erosion of roelj cliSs at 2-3

pedestal rocks at, erosion of the pedestal. 5-6
run-off and drip of rain water from.. 3-4
Limestone breccia, orgin and volume of... 113-114
Livingston ranch, N. Mex., wells in soluble

rocks on 115

Lower Blase Dale Glacier, Greenland, plate

showing end of.... 30

M

Massachusetts, central, dissected plateau of

plate showing 16

central, early Tertiary streams and

valleys in 18-23

extent of the area... 13-14

ground and terminal moraines in 39-47

later Tertiary stream adjustments in 23-27

pre- Wisconsin deposits in 37-39

recent epoch in 104-105

relations of the topography to the

rock formations in 27-29

summary of glacial history of 92-104

map of, showing distribution of drumlins 38
Moentopi formation, hillock of, covered with
gravel from Shinarump con-
glomerate, plate showing 4

Monadnocks, examples of 15

Monson, Mass., glacial lake at 79-81

Moraine, ground, in central Massachusetts.. 39-43
Moraines, terminal,jn central Massachusetts 43-47

N

Nashua Valley, Mass., adjustments of drain-
age in 23-27

Tertiary streams in 19-21

New Mexico, central, pedestal rocks in 10-11

O

Owens River, Cahf., pedestal rock in 126

pedestal rock in, plate showing . . . ^ 127

P

Palmer, Mass., glacial lake at 79-81

Pecos River at Red Bluff dam site, N. Mex.,

plate showing 112

Pecos Valley, N. Mex., analyses of waters

from 120

location of 107-108

rocks of 108

soluble material in 109

Pedestal rock, incipient, showing exfoliation,

plate showing 4

Pedestal rocks, in arid regions, forms and

origin of 1-11

in streams, descriptions of 123-128

plates showing 4

Pelham , Mass . , glacial lake near 84-85

Peneplain, Cretaceous, of central Massachu-
setts, development and dissection

of 15-18

Playa, plate showing 112

Page
Potholes in bed of Blackstone Elver, Mass.,

plate showing 104

Prospect Hill, near North Charlton, Mass.,

plate showing 38

Q

Quaternary deposits, three classes of 29

Quinsigamond quadrangle, Mass., diagram

showing retreat of glacier in. In pocket
map showing Quaternary geology of. In pocket
Quinsigamond Valley, Mass., Tertiary

streams in 21,27

R

Reservoirs on soluble rocks, leaks in 118-119

Russell, G. H., cited 11&-117

S

Salt, cavities dissolved in 114-116

Sand, cross-bedded, overlying laminated

clay, plate showing 71

Shinarump conglomerate, block of, with
vertical bedding planes, plate

showing 4

Sink holes, east of Carlsbad, N. Mex., plate

showing.. 112

produced by solution of salt and gypsum. 114-116

Southbridge, Mass., glacial lake near 78

Spokane, Wash . , basal t flows near 124

Stains on under side o f boul der, plate showing 4
Stream channels, glacial, in central Massa-
chusetts 55-56

Stream terraces, glacial, locations of 56-57

glacial, origin of 57-58

plate showing 58

Striae, glacial, directions of 34-36

Swift River, Mass., glacial history of 82-84

T

Till, glacial, plate showing hill of. 17

Travertine, deposition of, in Pecos VaUey 114

in Last Chance Canyon, N. Mex., plate

showing - 112

V

VermUion Cliffs, Ariz., plate showing 4

W
Wachusett Mountain, Mass., plate showing- 16
Ware quadrangle, Mass. , diagram showing re-
treat of glacier in In pocket

glacial lakes and streams of 75-92

map showing Quaternary geology of

In pocket

Ware River, Mass., glacial history of 81-82

Warren, Mass., glacial lake near 78

Water, kinds of, in the Pecos Valley, N.

Mex 119-121

Wind-blown sand, erosion by 6-7

Woolen mill, Gilbertville, Mass., plate show-
ing 105

Y

Yellowstone National Park, pedestal rock

in 127

pedestal rock in, plate showing 127

Department of the Interior

Hubert Work, Secretary

U. S. GEOLOGICAL SURVEY
George Otis Smith, Director

Bulletin 760

CONTRIBUTIONS TO THE GEOGRAPHY
OF THE UNITED STATES

1923-1924

MARIUS R. CAMPBELL

GEOLOGIST IN CHARGE

WASHINGTON

GOVERNMENT PRINTING OFFICE

1925

CONTENTS •

[The letters in parentheses preceding the titles are those used to designate the chapters for advance publi-
cation]

Page

(A) Pedestal rocks in the arid Southwest, by Kirk Bryan (published Dec. 15,

1923) 1

(B) The physical features of central Massachusetts, by W. C. Alden

(published Dec. 16, 1924) 13

(C) Erosion by solution and fill, by W. T. Lee (published April, 1925) 107

(D) Pedestal rocks in stream channels, by Kirk Bryan (published April,

1925) 123

Index 129

ILLUSTRATIONS

Page
Plate I. A, Vermihon and Shinarump cliffs from Lees Ferry, Ariz. ; B, Ped-
estal rock 4

II. A, Pedestal rock; , B, Block of conglomerate with vertical bed-
ding planes 4

III. A, Conical hillock of Moenkopi formation near Lees Ferry,

Ariz.; B, Incipient pedestal rock showing exfoliation 4

IV. A, Drip furrow below pedestal rock; B, Stains on under side of

boulder 4

V. A, Pedestal rock of granite; B, Pedestal rocks and boulders of

erosion ■ 4

VI. Map showing Quaternary geology of the Ware and Quinsiga-

mond quadrangles. Mass In pocket.

VII. Diagram showing stage of retreat of the glacial margin in the

Ware and Quinsigamond quadrangles, Mass In pocket.

VIII. A, Dissected plateau of central Massachusetts; B, Wachusett
Mountain, a monadnock rising above the plateau of central

Massachusetts 16

IX. A, Glacial till, a hill of unsorted glacial drift north of Clinton,
Mass.; B, Dana diorite ("ribbon gneiss") 1 mile southeast

of Gibbs Crossing, Ware, Mass 17

X. A, End of Lower Blase Dale Glacier, Disco Island, Greenland;
B, Glaciated rock surface near Lower Blase Dale Glacier,

Disco Island, Greenland 30

XL Glaciated rock ledge at CUnton, Mass 31

XII. A, Crumpled laminated clay, possibly interglacial; B, Esker

south of Clinton, Mass 38

XIII. Map of Massachusetts showing distribution of drumlins 38

XIV. A, Prospect Hill, a drumlin near North Charlton, Mass.; B,

Drumlin northeast of Gleasondale, Mass 38

XV. Flood plain and stream terrace 58

XVI. A, Walls of glacial boulders inclosing farm lands near Dana,

Mass.; 5, Glacial boulders near Princeton Center, Mass. _ 58
XVII. A, Glacial boulder north of Gilbertville, Mass.; B, Perched

boulders 3 miles northwest of Barre, Mass 58

XVIII. Map illustrating the relations of the ice front to glacial Lake

Nashua at the Clinton stage 70

XIX. A, Kettle holes in sand and gravel south of Clinton, Mass.; B,
Foreset and bottomset beds of sand plain 3 miles south-
west of Clinton, Mass 70

III

IV

CONTENTS

Page
Plate XX. A, Cross-bedded sand overlying laminated clay, Still River

Station, Mass.; B, Laminated and crumpled lacustrine

clay. Still River Station, Mass 71

XXI. A, B, Potholes in bed of Blackstone River, Mass 104

XXII. A, Barre Falls, Mass.; B, Woolen mill, Gilbertville, Mass 105

XXIII. A, Yeitso's Pillar, Carlsbad Cavern, N. Mex.; B, A partition

of onyx 112

XXIV. A, Stalactites; B, Hattin's Dome and the Temple of the

Sun, Carlsbad Cavern, N. Mex 112

XXV. A, Stalagmites and column; B, Spring deposits 112

XXVI. A, Pillars of onyx; B, Twin Domes, Carlsbad Cavern, N.

Mex 112

XXVII. A, Coralline stalagmites; B, A characteristic scene in Carls-
bad Cavern, N. Mex 112

XXVIII. Sink holes east of Carlsbad, N. Mex 112

XXIX. A, Pecos River at Red Bluff dam site, N. Mex.; B, A playa. 112
XXX. A, Entrance to Carlsbad Cavern, N. Max.; B, Travertine in

Last Chance Canyon, N. Mex 112

XXXI. A, Devils Top, Deep Creek canyon, 8 miles northwest of
Spokane, Wash.; B, Incipient pedestal rock, Columbia
River below China Bar, 9 miles downstream from junc-
tion of Spokane River, Wash 126

XXXII. A, Pedestal rock in Owens River, Inyo County, Calif.; B,
Pedestal rock in Gibbon River at Chocolate Cascade,

Yellowstone Park, Wyo 127

FiGxiRE 1. Map showing location of the Ware and Quinsigamond quad-
rangles, Mass 13

2. Map of central Massachusetts showing altitudes above sea level. 17

3. Diagram illlstrating stream changes in central Massachusetts. _ 20

4. Map of parts of New England, New York, and New Jersey,

showing extent, directions of movement, and terminal
moraines of the last great ice sheet 31

5. Map showing area covered by the great ice sheets in North

America at their maximum extension and the centers of ice
accumulation 32

6. Diagram showing probable origin of many kettle holes 45

7. Diagram illustrating formation of kame terraces 48

8. Diagram illustrating the relations of a branching sinuous gravel

ridge, or esker, near Westboro, Mass., to drumlins, a stream
valley, and a glacial terminal moraine 51

9. Diagram illustrating relations of the receding front of a

melting glacial globe and a later terminal moraine and out-
wash terrace to an earlier moraine and earlier terrace 57

10. Diagrams illustrating relations of the receding front of a

glacial lobe in Nashua River valley to glacial Lake Nashua

and the pitted terraces, or delta sand plains 63

11. Diagram illustrating relations of the ice front to glacial Lake

Nashua near the end of the Boylston stage 64

12. Map of Eddy County, N. Mex 107

13. Sketch section through Carlsbad, N. Mex 109

14. Map and profiles of Carlsbad Cavern National Monument,

N. Mex 111

15. Sketch section of cavernous rocks 118

16. Sketch section illustrating the filling of caverns 119

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BOSTON PUBLIC LIBRARY

3 9999 06625 092 7

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