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tudes 64 10' and 64 15'. The width of the ice was there found to
be 275 miles. Where the line of march began the ice descended to the
sea and formed a tide-water glacier, but on the west it did not reach within
about 14 miles of the head of Ameralik fiord, or 70 miles from the outer
coastline. The highest position of the vast convex covering of ice under
which the land is buried was 8920 feet. This elevation was reached at a
distance of 112 miles from the east coast. The gain in elevation for the
1 "The First Crossing of Greenland" (Longmans & Co., London, 1890), vol. 2, p. 468.



GLACIERS IN THE GREENLAND REGION. 141

tirst 15 miles was 220 feet per mile, and thence to the summit 38 feet per
mile. As the explorers proceeded westward from the summit the descent
was still more gentle, and for fully 100 miles averaged about 25 feet per
mile, a slope which no eye could distinguish from a perfect plain. A
cross profile of the inland ice was thus obtained, which shows a moderate
descent towards the ocean on either hand, with a broad, gently convex cen-
tral portion, and illustrates the form assumed by an ice sheet as the result
of accumulation at the surface and an outflow towards the margin.

The highly instructive journeys made by Peary in 1892, and repeated
in part in 1894 and still again in 1895, northeastward from Inglefield gulf
on the west coast, in about lat. 77 30', confirmed the conclusions reached
during the previous explorations referred to in respect to the character of
the Greenland ice sheet, and seemed to define its northern boundary, at
least in a general way. In the far north the coast exhibits the same
rugged character as at the south. The border of the inland ice is broken
by nunataks, but the central part forms a vast plain of snow over which
one may travel with dog-sleds and snow-shoes for hundreds of miles in a
continuous line without meeting serious obstructions. So far as the topog-
raphy is concerned it is only near the outer margin, where the ice flows
between rugged highlands and mountains tops project above its surface,
that serious difficulties to travel are met with. The highest point
reached on the broad, gently convex surface of the ice at the north was
about 8000 feet.

The principal lesson of geological interest learned from the study of the
continental glaciers covering Greenland is that such glaciers may originate
on land that is not mountainous and not elevated above the sea, and in
regions where the snowfall is not excessive.

Many of the hypotheses advanced to account for the previous exist-
ence of glaciers over northeastern North America and over north-
western Europe might be tested in the Greenland region at the present
day, and many of them, if so tested, it is safe to say, would be found
wanting. It is evident that the more familiar we become with existing
glaciers and with the climatic and topographic conditions on which they
depend, including a study of the currents and temperatures of the adjacent
sea, the better able we will be to interpret the records left by ancient
glaciers and to restore in fancy the condition of large portions of the earth
now thickly inhabited when covered by former ice sheets.

Our knowiedge of the glaciers of Greenland has been greatly extended
by observations made by Prof. T. C. Chamberlin in the summer of 1894,



142 GLACIERS OF NORTH AMERICA.

while connected with the second Peary relief expedition. The records of
the studies then made were not available when the book now before you
was written, although in revising it several references to them have been
introduced.

A condensed account was given by Chamberlin of his observations in
Greenland in the form of a presidential address before the Geological
Society of America, at Baltimore, in December, 1894, and subsequently
printed in the bulletin of the Society. l A much more extended record
has since been published in the Journal of Geology. 2 These reports con-
tain a critical and detailed account of glacial phenomena. Not only are
the actual conditions as they now exist in the portion of Greenland visited
minutely recorded, but general principles are discussed that have a bear-
ing on glacial phenomena in other regions and on the interpretation of the
records of formerly glaciated countries.

Among the more interesting results of these recent studies is the con-
firmation of the reports of previous travelers in reference to the character
of the precipitous and even overhanging precipices in which the glaciers
of the far north frequently end. The " Chinese Wall " described by Lock-
wood and Brainard, which, to persons familiar with glaciers in temperate
latitudes only, appeared to be such an abnormal feature, is shown by Cham-
berlin to be characteristic of the manner in which Arctic glaciers terminate.
Many of the photographic illustrations issued in connection with the
accounts of recent studies referred to bring out this feature with almost
startling reality. Two of these pictures, through the kindness of Pro-
fessor Chamberlin, are reproduced on Plate 22.

Another fact of great interest is the very definite stratification of many
of the glaciers in the far north. In this respect the sections displayed at
the extremities of the tongues of ice extending out from the central Green-
land sheet, resemble the sections exposed in the sides of crevasses in the
neve regions of more southern mountains. In fact, several of the phases
of the northern glaciers suggest that they correspond more nearly with the
neves of Alaska and of Alpine regions generally than they do with
"glaciers proper." In a certain sense they may be said to be examples of
"arrested development." The glaciers of the far north, it appears, are
frequently as definitely bedded and as beautifully laminated as the best
examples of sedimentary rocks. This resemblance to rock exposures is
still farther increased by the fact that in some instances the stratified ice

1 " Recent Glacial Studies in Greenland," Bull. Geol. Soc. Am., vol. 6, pp. 199-220.
2 Vols. 2, 3, and 4.



GLACTEKS OF NORTH .AMFIITCA.



PLATE 22.







FIG. A. FRONT OF BRYANT GLACIER, GREENLAND.
Showing vertical wall and stratification of the ice. (After T. C. Chamberlin )




FIG. B. PORTION OF SOUTHEAST FACE OF TUKTOO GLACIER, GREENLAND.

Showing projection of the upper layers and the fluting of their under surfaces. (After T. C. Chamberlin.)



GLACIERS IN THE GREENLAND REGION. 143

is folded and contorted in the manner frequently to be observed in gneiss
and schist, and is also faulted and overthrust. These structural features
may be seen in the Malaspina ice sheet and in other glaciers of temperate
regions, but nowhere, so far as known, on such a grand scale or such
clearness of details as in Greenland.

Accompanying and frequently intimately associated with the marked
stratification of the Greenland glaciers is the occurrence of debris in well-
defined layers. The scarps at the extremities of the glaciers, as stated by
Chamberlin, "usually present two great divisions, an upper tract of thick,
obscurely laminated layers of nearly white ice and a lower laminated tract
discolored by debris. At the base there is usually a talus slope, but only
sometimes a typical moraine. In the upper portion bluish solid layers
separate the more porous ice into minor divisions, and these are grouped
by consolidation into more massive layers. Sometimes the whole upper
division consists of a single stratum, but more commonly it is divided into
several great beds separated by quite distinct planes.

" The lower discolored divisions also sometimes consist of one great
stratum, but oftener it is divided into many thick layers, as in the case of
the white ice above. Very numerous partings further divide these .beds
into minor layers of varying thickness, grading down into delicate
laminations, a dozen or a score to an inch."

The two strongly marked divisions exhibited by this and numerous
associated glaciers seem to indicate that they were formed separately.
To one studying the photographs of these glaciers the marked contrast
between the upper and lower portions suggests that the upper layers
of clear ice have advanced upon the lower dirt-stained layers after the
debris they contain had been concentrated by melting. The two divi-
sions would thus represent two separate stages of ice advance. As
this explanation is not touched upon by Chamberlin, however, it is
probable that there are insuperable objections to it, and that the true
reason of the contrast referred to is less obvious and not fully under-
stood.

After discussing the various ways in which glaciers may become strati-
fied, Chamberlin summarized his conclusions as follows : " It would appear
that the stratification originated in the inequalities of deposition, empha-
sized by intercurrent winds, rain, and surface melting ; that the incipient
stratification may have been intensified by the ordinary processes of con-
solidation ; that shearing of the strata upon each other still further
emphasized the stratification and developed new horizons under favorable



144 GLACIERS OF NORTH AMERICA.

conditions ; that basal inequalities introduced new planes of stratification,
accompanied by earthy debris, and that this process extended itself so
far as even to form very minute laminae."

Another phenomenon displayed in a wonderful way at the extremities
of the Greenland glacier, and not previously noted in other regions, is the
manner in which certain layers jut out from the faces of the ice cliffs so as
to form projecting cornices. Their appearance is shown in Fig. B, Plate
22. These projections were seen on almost every one of the vertical gla-
cial faces examined, and were found to vary in width from a few inches to
one or two feet, and in rare cases to reach eight, ten, or fifteen feet. The
under surfaces of the cornices are frequently fluted, as may be seen in the
accompanying illustration. These cornices at first sight appear to be due
to a thrusting forward of the edge of an individual layer beyond the next
layer below. Movement along shearing planes seems, then, to be indicated.
As shown by Chamberlin, however, if this process is really in action, the
results produced by it in the unequal extension of various layers at the
extremities of the glaciers, are modified and masked to some extent by
unequal melting. Each layer of clear ice which projects so as to form a
cornice usually has a dark dirt-stained layer below it. The dark layer
absorbs heat more rapidly than the clear ice and is consequently melted
back more rapidly. The fluting on the under side of the cornices, which
it was supposed might be produced by the ice being pushed forward over
stones or inequalities in the layer beneath, was found on further study, to
be due, to a considerable extent at least, to water which trickled down, the
face of the overlying layer. In some instances, however, the junction
plane between a projecting layer and the stratum beneath was itself found
to be fluted. This and other evidence favors the idea that planes of shear
are the initial cause of the unequal projection of various layers in the
terminal escarpments. The development of such planes of shear seems at
first opposed to the commonly accepted explanation of the character of
glacial motion, but as the cornices are formed by the advance of layers
of clear ice over other dark layers, the shearing planes may be due to
unequal rigidity caused by the debris in the lower layer, and thus still be
in harmony with the hypothesis that ice flows as a plastic solid.

Measurements made by Lieutenant Peary, of the flow of Bowdoin
glacier, in about latitude 77 45', showed that the rate during the month of
July was four-tenths of a foot at the southwest point, near the east border,
and 2.78 feet at the farthest point, near the center, with an average of
1.89 feet for the whole.



GLACIERS IN THE GREENLAND REGION. 145

One of the most interesting of Chamberlin's discoveries, as previously
mentioned, is the presence of a small driftless area, on the shore of Bowdoin
bay, in which the rocks are deeply decayed. Evidence is thus furnished
that no great extension of ice in the region referred to has occurred within
recent geological times. It is to be remembered, however, that Ingefield
gulf is to the west and on the side of the great Greenland ice sheet, the
flow of which is supposed to be mainly southward. The tongues of ice
that come down to the sea, or approximately to that level, may be the
lateral drainage of the partially stagnant border of the main snow field,
and consequently would be less affected by an increase in accumulation
than the secondary glaciers farther south. 1

Since Chamberlin's visit to Greenland in connection with the second
Peary relief expedition, a third expedition of the same character visited
that region in the summer of 1895. Prof. R. D. Salisbury was a member
of this last company, and, it is to be expected, will make many additions
to the glacial observations previously obtained. Salisbury's reports will
probably be published in the Bulletin of the Geological Society of America
and in the Journal of Geology.

1 1 have been led to make this suggestion from certain occurrences observed in Alaska.
Marvin glacier, to the east of Mount St. Elias, flows past the head of a deep, high-grade lateral
valley without sending a tongue of ice into it. In ascending the lateral valley one sees in
front of him a wall of ice 150 or 200 feet high, formed by the border of Marvin glacier. The
ice in this wall is practically stagnant and protrudes but slightly into the lateral valley, although
the central current of the glacier flows past its entrance and joins the Malaspina ice sheet sev-
eral miles to the south. The conditions there seem to be similar, although on a much smaller
scale, to those found in the Ingefield region. It thus appears possible that a decided increase
in the main Greenland ice sheet might occur, the direction of flow being southward, without
greatly changing the conditions in the lateral ice tongues that branch off from the side of the
main current. These conditions may also account for the extreme sluggishness of the small
glaciers about Ingefield gulf.



CHAPTER VIII.

CLIMATIC CHANGES INDICATED BY THE GLACIERS OP
NORTH AMERICA. 1

IT has been shown by Dufor 2 and others that in general the glaciers
of Europe and Asia are retrograding ; that is, their extremities are with-
drawing farther and farther up the valley through which they flow. Sim-
ilar changes are known to be in progress in the glaciers of the southern
hemisphere, but whether a general recession is there in progress has not
been satisfactorily determined. The changes observed in the glaciers of
Europe and Asia make it important to ascertain if evidence of similar
climatic oscillations can be obtained from a study of the ice bodies of
North America. Whether the observed variations in the lengths of exist-
ing glaciers are wholly due to changes in their climatic environment, or
are influenced to some extent by other conditions, will be briefly con-
sidered in the closing paragraphs of this chapter.

In the preceding portion of this book several references have been
made to recent changes in the glacier described. The bearing of these
observations, however, on the study of the conditions governing the origin,
growth, and decadence of glaciers, and on still wider generalizations in
reference to the origin and decline of glacial epochs, is such as to warrant
some repetition.

The evidence thus far gathered concerning recent changes in the
glaciers of North America is remarkably consistent, and shows that with
the exception of a single glacier in Alaska and perhaps also of some of
the Greenland glaciers, they 'are all experiencing a general retreat. It
must be remembered, however, that no precise and accurate studies in this
connection have been made. Almost all of the information in hand is of
a qualitative character, obtained for the most part incidentally in connec-
tion with other studies. While the conclusion that the glaciers are
retreating is apparently well founded, more detailed observations will

1 This chapter is a reprint, with slight modifications, of a paper by the writer in the
American Geologist, vol. 9, 1892, pp. 322-336.

2 Bull. Soc. Vaud. Sc. Nat., vol. 17, 1881, pp. 422-425.






CLIMATIC CHANGES. 147

probably show that this is accomplished by many minor oscillations
which may include periods of local advance.

Character of the Evidence. Evidence of the advance or retreat of
the ends of alpine glaciers, or of the borders of piedmont and continental
glaciers, may be obtained in various ways. Glaciers which are advancing
sometimes plow into the debris in front of them and force it up in concen-
tric ridges, usually with the formation of cracks in the soil. The surfaces
of the ridges formed in this way are frequently covered with vegetation,
which in addition to their forms and the character of the material of which
they are composed, serves to distinguish them from terminal moraines.
When a glacier advances into a forest, the trees are broken off and piled
in confused heaps about the margin of the ice. The upper surface of a
glacier is known to flow faster than the ice below, and an advance is prob-
ably accomplished by the upper surface flowing over and burying the ice
hich rests on the ground. For this reason advancing glaciers usually
present bold scarps at their extremities, and in general, are not covered
with a broad sheet of debris.

In retreating glaciers the layers of new snow deposited on the neve
fields and changing to ice as they flow downward are melted before reach-
ing the end of the ice streams, and the slow-moving ice at the bottom is
thus left exposed and melts away. The retreat is accomplished not by a
contraction of the ice body, but by the melting of its distal extremity.
The ice which is not covered by the advance of fresh layers, melts at the
surface, and the englacial debris is concentrated at the surface. When
a sheet of debris of this character is extensive and covers the lower
portion of a glacier from side to side, it indicates that the ice beneath is
practically stationary and consequently is melting and retreating. The
ends of retreating glaciers frequently have a gentle surface slope, and in
many instances are so completely concealed by debris that the actual ter-
minus of the ice cannot be distinguished. When the moraines are heavy,
however, and especially when they are clothed with vegetation, the melt-
ing of the ice beneath is greatly retarded, and in some observed instances
the glaciers thus protected terminate in bold scarps.

When the end of a glacier recedes more 4 rapidly than soil can form on
the abandoned area, so as to admit of the growth of plants, a desolate
tract is left about its end, on which concentric lines of stones and boulders
may indicate halts in the retreat. Barren areas of this nature, when the
lack of vegetation is not due to the action of water from the ice, are good



148 GLACIERS OF NORTH AMERICA.

evidence of recent glacial recession. When glaciers which flow through a
valley having steep sides, become stagnant, a general lowering of the sur-
face, decreasing up stream, takes place, which leaves the bordering slopes
bare of vegetation. The action of rain and rills on such surfaces may
indicate to some extent the length of time they have been exposed. The
presence of fine glacial debris on slopes from which it would be easily
washed by rain may also furnish evidence in the same connection. Retreat-
ing glaciers sometimes leave detached masses of ice which are melted in
the course of a few years, and hence when present indicate rapid changes.
The amount of sub-aerial erosion on glaciated areas may also serve to
indicate the length of time they have been exposed.

These various classes of evidence usually enable one to determine defi-
nitely whether a glacier has recently advanced or retreated, and may some-
times afford a clue to the rate of these changes. When an opportunity is
afforded for detailed study, various surveying and photographic methods
may be employed. If observations can be continued season after season^ ]
the limits of a glacier at various times may be recorded by monuments, by
marking the position of its margin with asphaltum, etc. Instructions in this
connection have been published by Prof. H. F. Reid. 1 In the study of the
glaciers of America we have, with the exception of Muir glacier, no defi-
nite quantitative measurements, and must rely on such phenomena as have
been indicated.

California. Some of the small glaciers in the High Sierra, as already
described, have barren areas about their extremities, showing that they
are slowly receding. No measure of the rate of this recession has been
attempted.

Observations by J. S. Diller, of the United States Geological Survey,
on Mt. Shasta indicate that the glaciers in northern California, like those
farther south, are retreating. Evidence of this is furnished by barren
areas about the ends of several of the glaciers and by a conspicuous lateral
moraine on the side of the Whitney glacier, which in 1887, was about
twenty-five feet above the level of the adjacent ice.

Oregon and Washington. The glaciers on the Cascade mountains
have been visited by a number of persons, but I have been unable to

!"The Variations of Glaciers," Journal of Geology, vol. 3, 1895, pp. 278-288. This
paper contains references to other publications in which methods of observing changes in
glaciers are described.



CLIMATIC CHANGES. 149

obtain satisfactory evidence of advance or recession. An inspection of
photographs of the glaciers on Mount Rainier indicates that they end in
areas bare of vegetation, which presumably were recently occupied by
ice.

British Columbia. The glaciers of British Columbia, although
numerous and important, are but imperfectly known, and only a few
observations on recent changes have been made. Many of these glaciers,
however, have been seen by Dr. G. M. Dawson, who informs me that in
no instance are there evidences that they have recently advanced, and that
he considers it safe to assume that they are either stationary or slowly
receding.

R. G. McConnel, of the Canadian Geological Survey, has kindly
informed me that the glaciers, both on the Stikine river and in the
Rocky mountains, have shrunken back from fresh-looking moraines, and
that the intervals between the ice and the moraines, in all instances
examined by him, were destitute of trees and contained but little vege-
tation of any kind. In his opinion a marked retreat has occurred within
the last century or two, but whether it has been in progress during
the past one or two decades cannot be decided from the evidence in
hand. Observations made by Macoun and Ingersoll confirm this con-
clusion. 1

The Illecellewaet glacier at Glacier station, on the Canadian Pacific
Railroad, in the spring of 1891, was bordered by a barren area, between
the ice and the encircling forest, several hundred yards in breadth, which
had evidently been but recently abandoned by the glacier. A small
moraine on the western side of the glacier also suggested a recent shrink-
ing of the ice. The evidence of a recent retreat of this glacier has also
been noted by W. S. Green. 2

An absence of vegetation about the extremity of one of the glaciers on
Stikine river was noted by Blake, 3 and may probably be taken as an indi-
cation of a recent retreat of the ice. A legend current among the Stikine
Indians indicates that two glaciers on opposite sides of the stream were
formerly united and that the river then flowed through a tunnel beneath
the ice.

1 " Mountaineering in British Columbia," by Ernest Ingersoll, Bull. Am. Geog. Soc. r
vol. 18, 1880, p. 18.

2 "Among the Selkirk Glaciers," London, 1890, p. 69.

8 American Journal of Science, vol. 44, 1867, pp. 96-101.



150 GLACIERS OF NORTH AMERICA.

Alaska. The evidence that a general retreat of the glaciers of Alaska
is still in progress is abundant, and in a few instances is of quantitative
value.

L.ynn Canal. About this magnificent inlet, as previously described,
there are many ice streams of the alpine type, which descend nearly to sea
level, but none of them are now actually tide- water glaciers. About the
ends of many of them there are dense forests of spruce trees which must
have been growing for at least one hundred and fifty years, but between
the forests and the present terminus of the ice there is, in several instances,


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Online LibraryIsrael C. (Israel Cook) RussellGlaciers of North America; a reading lesson for students of geography and geology → online text (page 16 of 24)