Israel C. (Israel Cook) Russell.

Glaciers of North America; a reading lesson for students of geography and geology online

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by the glacier in its retreat, and alluvial material brought out from it by
swift, heavily laden streams, have been deposited about the margin of the
ice foot so as to form an encircling girdle now covered on its outer margin
with a dense spruce forest. On passing from the beach through the forest
for a distance of about a mile ; one comes to a barren, desolate tract of
boulders and gravel of fresh appearance, and evidently but recently
abandoned by the glacier. The barren area is perhaps half a mile broad,
and separates the extremity of the foot of the glacier throughout the entire
periphery of its expanded terminus from the encircling forest. From
archways in the ice there issue swift, roaring streams of muddy water,
much too strong and too deep for one to wade. These streams are heavily
loaded, and at once begin to deposit their burdens and to build up their
channels, so that their courses are unstable and new distributaries are formed
from time to time. Standing by the side of one of the streams as it issues
from its icy cavern, one may hear the clash of the boulders that are swept
along at the bottom of the turbid waters. The localities at which the
streams emerge from the ice are changed from time to time, so that the
entire area bordering the ice foot is torrent-swept and covered with
stream-borne deposits.

The ice at the lower extremity of Davidson glacier has a crystalline
appearance, much like coarsely crystallized dolomite. The banded struc-
ture generally so characteristic of glacial ice is not apparent in the ex-
posed surfaces. On climbing the rough crags of ice forming the immediate
foot of the glacier one finds stones and dirt scattered over its surface, but
a definite arrangement of the superficial debris in medial and lateral mo-
raines is not apparent in a near view. From a distance, however, as from
the decks of passing vessels, well-characterized medial bands looking like
roadways can be easily recognized, as well as broad, dirt-covered areas,
answering to lateral moraines, at the bases of the enclosing cliffs.

During my canoe trip down Lynn canal in 1889, I was storm-bound
for three days at Davidson glacier, and sought refuge in the sombre, moss-
covered forest about its foot. One cannot fully appreciate the varied
beauties of the dense forests of Alaska until he has actually lived in their
depths and witnessed the many changes that the primeval wilderness pre-
sents during storms and sunshine. The trees are large and rugged, and


frequently clothed, even to the ends of their topmost branches, with dense
coats of shaggy moss. Aged trunks long since dead and stripped of their
foliage, but still standing, assume strange, weird shapes, due to the thick
masses of mosses, lichens, and fungi that make their homes upon them.
Mosses and lichens cover the ground as with a dense mat a foot or more
thick, into which one sinks knee-deep at every step as if walking over a
bed of wet sponges. The trunks of fallen sachems of the forests are
buried from sight by a living mound of green and brown, most artistically
decorated with flowers and ferns. Every rod that one advances into the
moist and frequently mist-filled forests reveals new beauties, and fascinates
the fancy with harmonies of form and color not exceeded by those of the
moss-draped cypress and live-oak forests of Florida.

Along the shores of Lynn canal eastward from Davidson glacier, there
are other ice streams that drain the shining snow fields on the mountains
and add variety and beauty to the splendid scenery of that justly famed
arm of the sea ; but none of them reach tide water. The extremities of
the larger glaciers are hidden behind fringes of forests growing on the
deposits laid down during their slow retreat. To an observer on passing
vessels, the steep, broken surfaces of the ice streams, as they descend pre-
cipitous slopes, may be seen above the green of the forests into which they
seem to plunge. When the summits of the mountains are enshrouded in
mist the precipices of ice appear like frozen cataracts descending from the
clouds. The glaciers of Lynn canal that rank next to Davidson glacier in
size and beauty are the Auk, Eagle, Lemon creek, and Juneau. These
are all on the northeastern shore, and are better known than those on
the opposite coast because of their proximity to the beach. There are,
besides, hundreds of nameless glaciers that would well repay individual
study, of which glimpses may be had by those who pass in a day.


In traversing the deep valleys leading from the head of Lynn canal to
Chilkoot and Chilkat passes, one sees small glaciers on the adjacent
mountains. After passing the divide between the waters flowing directly
to the Pacific and those tributary to the rivers of the interior, other
similar glaciers occur which descend the northern slope of the mountains.
The timber line in the interior is far below the limit reached by the
glaciers, and the intervening area is barren and rugged, and strewn with
debris left by former ice streams. In the clefts between the more lofty


summits rising above the barren area, there are tongues of ice that descend
from snow fields, filling elevated valleys and amphitheatres about the
crests of the mountains. These glaciers all of the alpine type, are
usually of comparatively small size, and are the sources of many swift
streams of turbid water. Their extremities are seldom lower than 3000
or 4000 feet above sea level.

The general features of the region draining northward in the vicinity
of Lynn canal are believed to be characteristic of an extended belt of im-
perfectly explored country along the inland slope of the mountains
bordering the coast. Bold explorations made to the westward of Chilkat
pass, by E. J. Glave in 1890, and again in 1891, show that in the region
drained by Alsek river a wild, impetuous stream flowing through the
mountains bordering the coast and by numerous tributaries of the
Yukon, there are many alpine glaciers of the same general character as
those already referred to at the head of Chilkat pass.

Our knowledge of the glaciers draining to the interior was much ex-
tended in the summer of 1891 by important explorations made by Dr. C.
Willard Hayes * in company with Lieut. Frederick Schwatka. This ex-
pedition ascended Taku inlet, and after crossing a low divide reached the
head waters of the Yukon, and descended that stream in boats to Selkirk
house. Thence an overland journey was made westward to Copper river,
and an extended region explored on the northern flanks of the mountains
culminating in Mount Logan and Mount St. Elias. On gaining Copper
river the expedition descended that stream to the coast, and confirmed the
report of Lieut. H. T. Allen 2 in reference to the presence of glaciers near
the sea. The principal glaciers examined by Hayes lie at a distance of
50 to 80 miles to the north and northwest of Mount St. Elias, and are
described by him as follows in the paper just cited :

"Three large glaciers flow into the White River basin west of the
Alaskan boundary; and numerous streams, crossed while following the
southern bank of the upper White river, rise in small glaciers which do
not descend to the level of the valley.

" The largest glacier known to discharge wholly in the Yukon basin is
one which lies approximately on the 141st meridan, called the Klutlan,
from the native name of the river to which it gives rise. Its source is in

1 " An Expedition to the Yukon District," in National Geographic Magazine, vol. 4, 1892,
pp. 117-162.

2 "Report of an Expedition to the Copper, Tanana, and Koyukuk Rivers, Alaska,"
Washington, 1887, pp. 37-43.


the great snow fields between Mount St. Elias and the high peaks on the
northern border of the range called Nat-azh-at by the natives. It extends
several miles beyond the foot of the range, though it is rapidly receding
at the present time, and is between four and five miles broad where it
enters the valley. The stagnant ice in front of the retreating glacier is
buried under a great accumulation of morainal material continuous with
the terminal moraine, so that it is impossible to determine the exact limits
of the ice. The heavy mantle of vegetation which covers the terminal
moraine continues a mile or more beyond the outer edge of the ice, be-
coming gradually less abundant as the active portion of the glacier is

" The moraine in front of the Klutlan is the largest accumulated by
any of the interior glaciers. It is composed very largely of the white
volcanic tufa already described, but with this are mingled many apgular
fragments of amygdaloid lava and a few of granite and gneiss. Much of
the moraine has been removed by streams flowing from the glacier, but
remnants 200 feet or more in thickness extend nearly across to the high-
land north of the valley.

" The second of the White River glaciers is about midway between the
Klutlan and Scolai pass. It is much smaller than the Klutlan and does
not push out into the valley, but its front forms a wall of ice something
over a mile in length from side to side of the narrow valley in which it lies.

" The third and largest of the interior glaciers flows from the high moun-
tains northwest of Mount St. Elias down into Scolai pass, and from the
divide sends a lobe of ice toward White river and a smaller one toward
Copper River basin. This was named in honor of Mr. I. C. Russell. The
northern or White River lobe of Russell glacier is buried under a heavy
accumulation of moraine bearing some vegetation, while the southern lobe
is almost wholly free from morainal material, and the exposed ice has
melted down to the smooth convex surface and feather edge characteristic
of stagnant ice at the front of, a retreating glacier."

Taken altogether, the ice flowing northward from the St. Elias moun-
tains is insignificant in amount when compared with the vast frozen flood
that pours down through every valley, cation, and ravine on the southern
slope of the same uplift. The Seward glacier alone probably contains a
greater volume of ice than all the glaciers flowing into the White River
basin combined.

Space will not permit me to quote more fully from Dr. Hayes' instructive
description of the glacier seen by him, or to follow his discussion of the


climatic condition on which the distribution of the glaciers of Alaska
depends. His explorations denned the northern limit of the present ice
drainage and furnished additional information concerning the extent
inland of the glaciers of the same region in former times.


In the interior of Alaska and of the adjacent portion of Canada, there
are many mountains that reach elevations of at least four or five thousand
feet above the sea, but are bare of snow during the summer, and no glaciers
are known to exist upon them. This fact is the more striking for the
reason that several of the peaks referred to are near, and some of them
even north of the Arctic circle, and might be supposed to afford favorable
conditions for ice accumulation. A good illustration is thus furnished of
the conclusion long since reached, that the existence of perennial ice does
not necessarily depend upon latitude. The snow line when traced from
the most southerly peak in California that is snow-capped in summer,
northward along the Cordilleras, becomes lower and lower, until at the
base of Mount St. Elias it is only 2500 feet above the sea. North of the
St. Elias mountain belt, however, it rises abruptly, and so far as known is
not reached by any elevations in the interior.

The reason for the apparent anomaly in the distribution of the glaciers
of Alaska is to be found mainly in the direction of the currents of the
Pacific and in the topography of the land. A warm ocean current,
known as the Japan current, corresponding in many ways with the Gulf
stream, impinges on the southern shore of Alaska and greatly modifies
the condition of the atmosphere. The warm, humid winds from the south,
in passing over the mountains near the coast, part with a large share of
their moisture and descend to the lower regions to the north as com-
paratively dry winds. The snowfall on the mountains adjacent to the
coast is excessive, while in the interior it is light. At elevations ex-
ceeding 8000 or 10,000 feet on the mountains near the sea every storm
throughout the year is accompanied with snow, and above 13,000 feet
it is safe to say that rain never falls. In the interior, however, not only
is a snowstorm in summer unknown, but rain seldom falls during that
season. In winter the prevailing air currents of the interior are from
the frozen sea to the northward, and are in general dry winds, for the
reason that they travel from cold to warmer regions and tend to absorb
rather than to precipitate moisture. The mean annual temperature, and


still more markedly the mean winter temperature of the interior, is far
below what it is at corresponding elevations on the coast, but, for reasons
already stated, this is not necessarily favorable to the accumulation of
perennial snow.

The glaciers of Alaska illustrate the well-known fact that the most
favorable conditions for ice accumulation are found where a region of
condensation is adjacent to a region of active evaporation.

The influence of climatic and topographic conditions on the existence
of glaciers, just referred to, is again strikingly shown in the far northwest
by the records of former periods of maximum ice extension. During the
glacial period the ice fields adjacent to the Pacific were more extensive
than at present, but were confined to the same general region. The
glaciers that flowed northward in the vicinity of Mount St. Elias reached
only about 100 miles inland. All of the central and northern portions
of Alaska were unglaciated.


Glaciers of the alpine type similar to those on the shores of Lynn
canal are known to exist in the mountain-enclosed valleys on the border of
Cook's inlet, and, in diminishing numbers and decreasing size, from there
westward on the Alaskan peninsula and on some of the more rugged of
the Aleutian islands. The positions of a few small glaciers on the
borders of Cook's inlet are shown on the charts published by the U. S.
Coast and Geodetic Survey, but no description of them has ever been
published. The verbal reports of traders and hunters who have visited
that region indicate that the snow fields crowning the mountains are ex-
tensive and that the glaciers flowing from them are well worthy of con-
sideration. The snow line appears to have an elevation of some three or
four thousand feet, and the glaciers are mostly individual tongues of ice
descending to within a few hundred feet of the sea. None of them now
reach tide water.

The most extensive of the isolated snow fields on the Aleutian islands
yet reported cluster about the summit of Mount Makushin, the highest
peak on Iluliuk island. A view of that imposing peak rising white and
shining above a most rugged setting of lesser mountains, obtained by the
writer from a commanding summit on the eastern portion of the same
island, showed that the glaciers on its sides are small and similar in many
ways to those of the High Sierra. Their lower limit appears to be about


4500 feet above the sea, but the distance rendered it impossible to deter-
mine special characteristics. Some of the volcanic piles on the Aleutian
islands to the west of Iluliuk are higher than Mount Makushin, and are
known to be snow-covered in summer ; but no definite information in
reference to the presence of glaciers on them is available. It is to be ex-
pected that the great Cordilleran glacier belt, when traced westward from
peak to peak on the Aleutian islands, will rise higher and higher, and that
the glacier will at the same time diminish in size, until at last the topo-
graphic and climatic conditions will preclude their existence. Where the
extreme western tip of the crescent formed by the Cordilleran glacier belt
actually terminates remains to be determined.


Some account has already been given of the alpine glaciers on the
southern slope of the mountains that culminate in Mount Logan and
Mount St. Elias. Many of these ice streams descend onto a low plain
intervening between the mountains and the sea, and there expand and
unite one with another, so as to form vast lake-like bodies of ice to which
the term piedmont glaciers has been applied. Two broad ice sheets of
this nature, named in honor of the distinguished navigators Malaspina
and Bering respectively, are now known, but only the former has been
visited. Bering glacier has been seen from vessels passing along the coast
to the westward of Mount St. Elias, but no explorer has as yet set foot
upon it.


(A sketch map of Malaspina glacier forms Plate 17.)

Area. The Malaspina glacier, as indicated on Plate 17, extends with
unbroken continuity from Yakutat bay 70 miles westward, and has an
average breadth of between 20 and 25 miles. Its area is approximately
1500 square miles, or intermediate in extent between the area of the
state of Rhode Island and the area of the state of Delaware.

It is a vast, nearly horizontal plateau of ice. The general elevation of
its surface at a distance of five or six miles from its outer border is about
1500 feet. The central portion is free from moraines or dirt of any kind,
but is rough and broken by thousands and tens of thousands of crevasses.
Its surface, when not concealed by moraines, is broadly undulating, and
recalls the appearance of the rolling prairie lands west of the Mississippi.


From the higher swells on its surface one may see for many miles in all
directions without observing a single object to break the monotony of the
frozen plain. So vast is the glacier that, on looking down on it from
elevations of two or three thousand feet above its surface, its limits are
beyond the reach of vision.

Lobes. The glacier consists of three principal lobes, each of which is
practically the expansion of a large tributary ice stream. The largest has
an eastward flow, toward Yakutat bay, and is supplied mainly by the
Seward glacier. The next lobe to the west is the expanded terminus of
the Agassiz glacier ; its current is toward the southwest. The third great
lobe lies between the Chaix and Robinson hills, and its main supply of ice
is from the Tyndall and Guyot glaciers. Its central current is southward.
The direction of flow in the several lobes explains the distribution of the
moraines about their borders.

The Seward lobe melts away before reaching Yakutat bay and ends
with a low frontal slope, but its southern margin has been eaten into by
the ocean, so as to form the Sitkagi bluffs. The Agassiz lobe is complete,
and is fringed all about its outer border by broad moraines. The Guyot
lobe pushes boldly out into the ocean, and, breaking off, forms magnificent
ice cliffs.

Characteristics of the Noii-moraine-covered Surface. On the

northern border of the glacier, but below the line of perpetual snow, where
the great plateau of ice has a gentle slope, the surface melting gives
origin to hundreds of rills and rivulets which course along in channels of
clear ice until they meet a crevasse or moulin and plunge down into the
body of the glacier to join the drainage beneath. On warm summer days,
when the sun is well above the horizon, the murmur of streams may be
heard wherever the ice surface is inclined and not greatly broken ; but as
soon as the shadows of evening cross the ice fields, melting ceases and the
silence is unbroken. These streams are always of clear, sparkling water,
and it is seldom that their channels contain debris. Where the surface of
the glacier is nearly level, and especially when broken by crevasses, sur-
face streams are absent, although the clefts in the ice are frequently filled
with water. The moulins in which the larger of the surface streams
usually disappear are well-like holes of great depth. They are seldom
straight, however, as the water in plunging into them usually strikes the
opposite side and causes it to melt away more rapidly than the adjacent


surfaces. The water in descending is dashed from side to side and in-
creases their irregularities. A deep roar coming from the hidden chambers
to which the moulins lead frequently tells that large bodies of water are
rushing along the ice caves beneath. In the southern portion of the
glacier, where the ice has been deeply melted, and especially where large
crevasses occur, the abandoned tunnels made by englacial streams are
sometimes revealed. These tunnels are frequently 10 or 15 feet high,
and occasionally one may pass through them from one depression in the
glacier to another. In some instances they are floored with debris, some
of which is partially rounded. As melting progresses this material is con-
centrated at the surface as a moraine.

The ice in the various portions of the glacier was observed to be
formed of alternate blue and white bands, as is the rule in glacial ice
generally. The blue bands are of compact ice, while the white bands are
composed of ice filled with air cavities. The banded structure is usually
nearly vertical, but the dip, when noticeable, is northward. Nearly
parallel with the blue and white layers, but crossing them at low angles,
there are frequently bands of hard, blue ice several hundred feet long and
two or three inches in thickness which have a secondary origin, and are
due to the freezing of waters in fissures.

The rapid melting of the surface produces many curious phenomena,
which, as explained in a previous chapter, are common to many ice bodies
below the line of perpetual snow. The long belts of stone and dirt form-
ing the moraines protect the ice beneath from the action of the sun and
air, while adjacent surfaces waste away. The result of this differential
melting is that the moraines become elevated on ridges of ice. The forms
of the ridges vary according to the amount and character of the debris
resting upon them. In places they are steep and narrow, and perhaps
150 or 200 feet high. From a little distance they look like solid masses
of debris, and resemble great railroad embankments, but on closer exami-
nation they are seen to be ridges of ice, covered with a thin sheet of earth
and stones. The sides of such ridges are exceedingly difficult to climb,
owing to the looseness of the stones, which slide from beneath one's feet
and roll down the slopes. The larger boulders are the first to be dis-
lodged by the melting of the ice, and rolling down the sides of the
ridges, form a belt of coarse debris along their margins. In this way a
marked assortment of the debris in reference to size and shape frequently
takes place. In time the narrow belts of large boulders become elevated in
their turn and form the crests of secondary ridges. Rocks rolling down


the steep slopes are broken into finer and finer fragments and are reduced
in part to the condition of sand and clay. When the debris is sufficiently
comminuted it is sometimes carried away by surface streams and washed
into crevasses and moulins. Not all of the turbidity of the subglacial
streams can be charged to the grinding of the glacier over the rocks on
which it rests, as a limited portion of it certainly comes from the crushing
of the surface moraines during their frequent changes of position.

Isolated blocks of stone lying on the glacier, when of sufficient size
not to be warmed through by the sun's heat in a single day, also protect
the ice beneath and retain their position as the adjacent surface melts, so
as to rest on pedestals frequently several feet high. These elevated
blocks are usually flat, angular masses, sometimes 20 feet or more in
diameter. Owing to the greater effect of the sun on the southern side of
the columns which support them, the tables are frequently inclined .south-
ward, and ultimately slide off their pedestals in that direction. No sooner
has a block fallen from its support, however, than the process is again
initiated, and it is again left in relief as the adjacent surface melts. The
many falls which the larger blocks receive in this manner cause them to
become broken, thus illustrating another phase of the process of comminu-

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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 12 of 24)