EXISTING GLACIERS.
_In Europe._--Our specific account of existing glaciers naturally begins
with those of the Alps, where Hugi, Charpentier, Agassiz, Forbes, and
Guyot, before the middle of this century, first brought clearly to light
the reality and nature of glacial motion.
According to Professor Heim, of Zürich, the total area covered by the
glaciers and ice-fields of the Alps is upwards of three thousand square
kilometres (about eleven hundred square miles). The Swiss Alps alone
contain nearly two-thirds of this area. Professor Heim enumerates 1,155
distinct glaciers in the region. Of these, 144 are in France, 78 in
Italy, 471 in Switzerland, and 462 in Austria.
Desor describes fourteen principal glacial districts in the Alps, the
westernmost of which is that of Mont Pelvoux, in Dauphiny, and the
easternmost that in the vicinity of the Gross Glockner, in Carinthia. The
most important of the Alpine systems are those which are grouped around
Mont Blanc, Monte Rosa, and the Finsteraarhorn, the two former peaks
being upwards of fifteen thousand feet in height, and the latter upwards
of fourteen thousand. The area covered by glaciers and snow-fields
in the Bernese Oberland, of which Finsteraarhorn is the culminating
point, is about three hundred and fifty square kilometres (a hundred
square miles), and contains the Aletsch Glacier, which is the longest
in Europe, extending twenty-one kilometres (about fourteen miles) from
the _névé_-field to its foot. The Mer de Glace, which descends from Mont
Blanc to the valley of Chamounix, has a length of about eight miles
below the _névé_-field. In all, there are estimated to be twenty-four
glaciers in the Alps which are upwards of four miles long, and six which
are upwards of eight miles in length. The principal of these are the Mer
de Glace, of Chamounix, on Mont Blanc; the Gorner Glacier, near Zermatt,
on Monte Rosa; the lower glacier of the Aar, in the Bernese Oberland;
and the Aletsch Glacier and Glacier of the Rhône, in Vallais; and the
Pasterzen, in Carinthia.
[Illustration: Fig. 7.--Mount Blanc Glacier Region: _m_, Mer de Glace;
_g_, Du Géant; _l_, Leschaux; _t_, Taléfre; _B_, Bionassay; _b_, Bosson.]
These glaciers adjust themselves to the width of the valleys down which
they flow, in some places being a mile or more in width, and at others
contracting into much narrower compass. The greatest depth which Agassiz
was able directly to measure in the Aar Glacier was two hundred and
sixty metres (five hundred and twenty-eight feet), but at another point
the depth was estimated by him to be four hundred and sixty metres (or
fifteen hundred and eighty-four feet).
The glaciers of the Alps are mostly confined to the northern side and
to the higher portions of the mountain-chain, none of them descending
below the level of four thousand feet, and all of them varying slightly
in extent, from year to year, according as there are changes in the
temperature and in the amount of snow-fall.
The Pyrenees, also, still maintain a glacial system, but it is of
insignificant importance. This is partly because the altitude is much
less than that of the Alps, the culminating point being scarcely more
than eleven thousand feet in height. Doubtless, also, it is partly due to
the narrowness of the range, which does not provide gathering-places for
the snow sufficiently extensive to produce large glaciers. The snow-fall
also is less upon the Pyrenees than upon the Alps. As a consequence of
all these conditions, the glaciers of the Pyrenees are scarcely more
than stationary _névé_-fields lingering upon the north side of the range.
The largest of these is near Bagnères de Luchon, and sends down a short,
river-like glacier.
In Scandinavia the height of the mountains is also much less than that of
the Alps, but the moister climate and the more northern latitude favours
the growth of glaciers at a much lower level North of the sixty-second
degree of latitude, the plateaus over five thousand feet above the sea
pretty generally are gathering-places for glaciers. From the Justedal a
snow-field, covering five hundred and eighty square miles, in latitude
62°, twenty-four glaciers push outwards towards the German Sea, the
largest of which is five miles long and three-quarters of a mile wide.
The Fondalen snow-field, between latitudes 66° and 67°, covers an
area about equal to that of the Justedal; but, on account of its more
northern position, its glaciers descend through the valleys quite to the
ocean-level. The Folgofon snow-field is still farther south, but, though
occupying an area of only one hundred square miles, it sends down as many
as three glaciers to the sea-level. The total area of the Scandinavian
snow-fields is about five thousand square miles.
In Sweden Dr. Svenonius estimates that there are, between latitudes 67°
and 68-1/2°, twenty distinct groups of glaciers, covering an area of four
hundred square kilometres (one hundred and forty-four square miles), and
he numbers upwards of one hundred distinct glaciers of small size.
As is to be expected, the large islands in the Polar Sea north of Europe
and Asia are, to a great extent, covered with _névé_-fields, and numerous
glaciers push out from them to the sea in all directions, discharging
their surplus ice as bergs, which float away and cumber the waters with
their presence in many distant places.
[Illustration: Fig. 8.--The Svartisen Glacier on the west coast of
Norway, just within the Arctic circle, at the head of a fiord ten miles
from the ocean. The foot of the Glacier is one mile wide, and a quarter
of a mile back from the water. Terminal moraine in front. (Photographed
by Dr. L. C. Warner.)]
The island of Spitzbergen, in latitude 76° to 81°, is favourably situated
for the production of glaciers, by reason both of its high northern
latitude, and of its relation to the Gulf Stream, which conveys around
to it an excessive amount of moisture, thus ensuring an exceptionally
large snow-fall over the island. The mountainous character of the island
also favours the concentration of the ice-movement into glaciers of vast
size and power. Still, even here, much of the land is free from snow and
ice in summer. But upon the northern portion of the island there is an
extensive table-land, upwards of two thousand feet above the sea, over
which the ice-field is continuous. Four great glaciers here descend to
tide-water in Magdalena Bay. The largest of these presents at the front a
wall of ice seven thousand feet across and three hundred feet high; but,
as the depth of the water is not great, few icebergs of large size break
off and float away from it.
Nova Zembla, though not in quite so high latitude, has a lower mean
temperature upon the coasts than Spitzbergen. Owing to the absence of
high lands and mountains, however, it is not covered with perpetual snow,
much less with glacial ice, but its level portions are "carpeted with
grasses and flowers," and sustain extensive forests of stunted trees.
Franz-Josef Land, to the north of Nova Zembla, both contains high
mountains and supports glaciers of great size. Mr. Payer conducted a
sledge party into this land in 1874, and reported that a precipitous wall
of glacial ice, "of more than a hundred feet in height, formed the usual
edge of the coast." But the motion of the ice is very slow, and the ice
coarse-grained in structure, and it bears a small amount only of morainic
material. So low is here the line of perpetual snow, that the smaller
islands "are covered with caps of ice, so that a cross-section would
exhibit a regular flat segment of ice." It is interesting to note, also,
that "many ice-streams, descending from the high _névé_ plateau, spread
themselves out over the mountain-slopes," and are not, as in the Alps,
confined to definite valleys.
Iceland seems to have been properly named, since a single one of the
snow-fields--that of Vatnajoküll, with an extreme elevation of only six
thousand feet--is estimated by Helland to cover one hundred and fifty
Norwegian square miles (about seven thousand English square miles), while
five other ice-fields (the Langjoküll, the Hofsjoküll, the Myrdalsjoküll,
the Drangajoküll, and the Glamujoküll) have a combined area of ninety-two
Norwegian or about four thousand five hundred English square miles. The
glaciers are supposed by Whitney to have been rapidly advancing for some
time past.
_In Asia._--Notwithstanding its lofty mountains and its great extent
of territory lying in high latitudes, glaciers are for two reasons
relatively infrequent: 1. The land in the more northern latitudes is low.
2. The dryness of the atmosphere in the interior of the continent is such
that it unduly limits the snow-fall. Long before they reach the central
plateau of Asia, the currents of air which sweep over the continent from
the Indian Ocean have parted with their burdens of moisture, having left
them in a snowy mantle upon the southern flanks of the Himalayas. As a
result, we have the extensive deserts of the interior, where, on account
of the clear atmosphere, there is not snow enough to resist continuously
the intense activity of the unobstructed rays of the sun.
In spite of their high latitude and considerable elevation above the
sea-level, glaciers are absent from the Ural Mountains, for the range is
too narrow to afford _névé_-fields of sufficient size to produce glaciers
of large extent.
The Caucasus Mountains present more favourable conditions, and for a
distance of one hundred and twenty miles near their central portion
have an average height of 12,000 feet, with individual peaks rising to
a height of 16,000 feet or more; but, owing to their low latitude, the
line of perpetual snow scarcely reaches down to the 11,000-foot level. So
great are the snow-fields, however, above this height that many glaciers
push their way down through the narrow mountain-gorges as far as the
6,000-foot level.
The Himalaya Mountains present many favourable conditions for the
development of glaciers of large size. The range is of great extent and
height, thus affording ample gathering-places for the snows, while the
relation of the mountains to the moisture-laden winds from the Indian
Ocean is such that they enjoy the first harvest of the clouds where
the interior of Asia gets only the gleanings. As is to be expected,
therefore, all the great rivers which course through the plains of
Hindustan have their rise in large glaciers far up towards the summits of
the northern mountains. The Indus and the Ganges are both glacial streams
in their origin, as are their larger tributary branches--the Basha, the
Shigar, and the Sutlej. Many of the glaciers in the higher levels of
the Himalaya Mountains where these streams rise have a length of from
twenty-five to forty miles, and some of them are as much as a mile and
a half in width and extend for a long distance, with an inclination as
small as one degree and a half or one hundred and thirty-eight feet to a
mile.
In the Mustagh range of the western Himalayas there are two adjoining
glaciers whose united length is sixty-five miles, and another not far
away which is twenty-one miles long and from one to two miles wide in its
upper portion. Its lower portion terminates at an altitude of 16,000 feet
above tide, where it is three miles wide and two hundred and fifty feet
thick.
_Oceanica._---Passing eastward to the islands of the Pacific Ocean, New
Zealand is the only one capable of supporting glaciers. Their existence
on this island seems the more remarkable because of its low latitude
(42° to 45°); but a grand range of mountains rises abruptly from the
water on the western coast of the southern island, culminating in Mount
Cook, 13,000 feet above the sea, and extending for a distance of about
one hundred miles. The extent and height of this chain, coupled with
the moisture of the winds, which sweep without obstruction over so
many leagues of the tropical Pacific, are specially favourable to the
production of ice-fields of great extent. Consequently we find glaciers
in abundance, some of which are not inferior in extent to the larger ones
of the Alps. The Tasman Glacier, described by Haas, is ten miles long
and nearly two miles broad at its termination, "the lower portion for a
distance of three miles being covered with morainic _detritus_." The
Mueller Glacier is about seven miles long and one mile broad in its lower
portion.
_South America._--In America, existing glaciers are chiefly confined to
three principal centres, namely, to the Andes, south of the equator; to
the Cordilleras, north of central California; and to Greenland.
In South America, however, the high mountains of Ecuador sustain a few
glaciers above the twelve-thousand-foot level. The largest of these are
upon the eastern slope of the mountains, giving rise to some of the
branches of the Amazon--indeed, on the flanks of Cotopaxi, Chimborazo,
and Illinissa there are some glaciers in close proximity to the equator
which are fairly comparable in size to those of the Alps.
In Chili, at about latitude 35°, glaciers begin to appear at lower
levels, descending beyond the six-thousand-foot line, while south of this
both the increasing moisture of the winds and the decreasing average
temperature favour the increase of ice-fields and glaciers. Consequently,
as Darwin long ago observed, the line of perpetual snow here descends to
an increasingly lower level, and glaciers extend down farther and farther
towards the sea, until, in Tierra del Fuego, at about latitude 45°, they
begin to discharge their frozen contents directly into the tidal inlets.
Darwin's party surveyed a glacier entering the Gulf of Penas in latitude
46° 50', which was fifteen miles long, and, in one part, seven broad. At
Eyre's Sound, also, in about latitude 48°, they found immense glaciers
coming clown to the sea and discharging icebergs of great size, one of
which, as they encountered it floating outwards, was estimated to be "_at
least_ one hundred and sixty-eight feet in total height."
In Tierra del Fuego, where the mountains are only from three thousand
to four thousand feet in height and in latitude less than 55°, Darwin
reports that "every valley is filled with streams of ice descending to
the sea-coast," and that the inlets penetrated by his party presented
miniature likenesses of the polar sea.
[Illustration: Fig. 9.--Floating berg, showing the proportions above and
under the water. About seven feet under water to one above.]
_Antarctic Continent._--Of the so-called Antarctic Continent little is
known; but icebergs of great size are frequently encountered up to 58°
south latitude, in the direction of Cape Horn, and as far as latitude
33° in the direction of Cape of Good Hope. Nearly all that is known
about this continent was discovered by Sir J. C. Ross during the period
extending from 1839 to 1843, when, between the parallels of 70° and 78°
south latitude, he encountered in his explorations a precipitous mountain
coast, rising from seven thousand to ten thousand feet above tide.
Through the valleys intervening between the mountain-ranges huge glaciers
descended, and "projected in many places several miles into the sea and
terminated in lofty, perpendicular cliffs. In a few places the rocks
broke through their icy covering, by which alone we could be assured that
land formed the nucleus of this, to appearance, enormous iceberg."[AG]
[Footnote AG: Quoted by Whitney in Climatic Changes, p. 314.]
Again, speaking of the region in the vicinity of the lofty volcanoes
Terror and Erebus, between ten thousand and twelve thousand feet high,
the same navigator says:
"We perceived a low, white line extending from its extreme eastern
point, as far as the eye could discern, to the eastward. It presented
an extraordinary appearance, gradually increasing in height as we got
nearer to it, and proving at length to be a perpendicular cliff of ice,
between one hundred and fifty and two hundred feet above the level of
the sea, perfectly flat and level at the top, and without any fissures
or promontories on its even, seaward face. What was beyond it we could
not imagine; for, being much higher than our mast-head, we could not
see anything except the summit of a lofty range of mountains extending
to the southward as far as the seventy-ninth degree of latitude. These
mountains, being the southernmost land hitherto discovered, I felt
great satisfaction in naming after Sir Edward Parry.... Whether Parry
Mountains again take an easterly trending and form the base to which this
extraordinary mass of ice is attached, must be left for future navigators
to determine. If there be land to the southward it must be very remote,
or of much less elevation than any other part of the coast we have seen,
or it would have appeared above the barrier."
This ice-cliff or barrier was followed by Captain Ross as far as 198°
west longitude, and found to preserve very much the same character during
the whole of that distance. On the lithographic view of this great
ice-sheet given in Ross's work it is described as "part of the South
Polar Barrier, one hundred and eighty feet above the sea-level, one
thousand feet thick, and four hundred and fifty miles in length."
A similar vertical wall of ice was seen by D'Urville, off the coast of
Adelie Land. He thus describes it: "Its appearance was astonishing. We
perceived a cliff having a uniform elevation of from one hundred to one
hundred and fifty feet, forming a long line extending off to the west....
Thus for more than twelve hours we had followed this wall of ice, and
found its sides everywhere perfectly vertical and its summit horizontal.
Not the smallest irregularity, not the most inconsiderable elevation,
broke its uniformity for the twenty leagues of distance which we followed
it during the day, although we passed it occasionally at a distance of
only two or three miles, so that we could make out with ease its smallest
irregularities. Some large pieces of ice were lying along the side of
this frozen coast; but, on the whole, there was open sea in the offing."
[AH]
[Footnote AH: Whitney's Climatic Changes, pp. 315, 316.]
[Illustration: Fig. 10.--Iceberg in the Antarctic Ocean.]
_North America._--In North America living glaciers begin to appear in
the Sierra Nevada Mountains, in the vicinity of the Yosemite Park, in
central California. Here the conditions necessary for the production
of glaciers are favourable, namely, a high altitude, snow-fields of
considerable extent, and unobstructed exposure to the moisture-laden
currents of air from the Pacific Ocean. Sixteen glaciers of small size
have been noted among the summits to the east of the Yosemite; but none
of them descend much below the eleven-thousand-foot line, and none of
them are over a mile in length. Indeed, they are so small, and their
motion is so slight, that it is a question whether or not they are to be
classed with true glaciers.
Owing to the comparatively low elevation of the Sierra Nevada north of
Tuolumne County, California, no other living glaciers are found until
reaching Mount Shasta, in the extreme northern part of the State. This
is a volcanic peak, rising fourteen thousand five hundred feet above the
sea, and having no peaks within forty miles of it as high as ten thousand
feet; yet so abundant is the snow-fall that as many as five glaciers are
found upon its northern side, some of them being as much as three miles
long and extending as low down as the eight-thousand-foot level. Upon the
southern side glaciers are so completely absent that Professor Whitney
ascended the mountain and remained in perfect ignorance of its glacial
system. In 1870 Mr. Clarence King first discovered and described them on
the northern side.
North of California glaciers characterise the Cascade Range in increasing
numbers all the way to the Alaskan Peninsula. They are to be found upon
Diamond Peak, the Three Sisters, Mount Jefferson, and Mount Hood, in
Oregon, and appear in still larger proportions upon the flanks of Mount
Rainier (or Tacoma) and Mount Baker, in the State of Washington. The
glacier at the head of the White River Valley is upon the north side of
Rainier, and is the largest one upon that mountain, reaching down to
within five thousand feet of the sea-level, and being ten miles or more
in length. All the streams which descend the valleys upon this mountain
are charged with the milky-coloured water which betrays their glacial
origin.
[Illustration: Fig. 11.--Map of Southeastern Alaska. The arrow-points
mark glaciers.]
In British Columbia, Glacier Station, upon the Canadian Pacific Railroad,
in the Selkirk Mountains, is within half a mile of the handsome
Illicilliwaet Glacier, while others of larger size are found at no great
distance. The interior farther north is unexplored to so great an extent
that little can be definitely said concerning its glacial phenomena. The
coast of British Columbia is penetrated by numerous fiords, each of which
receives the drainage of a decaying glacier; but none are in sight of the
tourist-steamers which thread their way through the intricate network of
channels characterising this coast, until the Alaskan boundary is crossed
and the mouth of the Stickeen River is passed.
A few miles up from the mouth of the Stickeen, however, glaciers of
large size come down to the vicinity of the river, both from the north
and from the south, and the attention of tourists is always attracted
by the abundant glacial sediment borne into the tide-water by the river
itself and discolouring the surface for a long distance beyond the
outlet. Northward from this point the tourist is rarely out of sight of
ice-fields. The Auk and Patterson Glaciers are the first to come into
view, but they do not descend to the water-level. On nearing Holcomb
Bay, however, small icebergs begin to appear, heralding the first of the
glaciers which descend beyond the water's edge. Taku Inlet, a little
farther north, presents glaciers of great size coming down to the
sea-level, while the whole length of Lynn Canal, from Juneau to Chilkat,
a distance of eighty miles, is dotted on both sides by conspicuous
glaciers and ice-fields.
The Davidson Glacier, near the head of the canal, is one of the most
interesting for purposes of study. It comes down from an unknown
distance in the western interior, bearing two marked medial moraines upon
its surface. On nearing tide-level, the valley through which it flows is
about three-quarters of a mile in width; but, after emerging from the
confinement of the valley, the ice spreads out over a fan-shaped area
until the width of its front is nearly three miles. The supply of ice
not being sufficient to push the front of the glacier into deep water,
equilibrium between the forces of heat and cold is established near the
water's edge. Here, as from year to year the ice melts and deposits its
burdens of earthy _débris_, it has piled up a terminal moraine which
rises from two hundred to three hundred feet in height, and is now
covered with evergreen trees of considerable size. From Chilkat, at the
head of Lynn Canal, to the sources of the Yukon River, the distance is
only thirty-five miles, but the intervening mountain-chain is several
thousand feet in height and bears numerous glaciers upon its seaward side.
About forty miles west of Lynn Canal, and separated from it by a range
of mountains of moderate height, is Glacier Bay, at the head of one of
whose inlets is the Muir Glacier, which forms the chief attraction for
the great number of tourists that now visit the coast of southeastern
Alaska during the summer season. This glacier meets tide-water in
latitude 58° 50', and longitude 136° 40' west of Greenwich. It received
its name from Mr. John Muir, who, in company with Rev. Mr. Young, made
a tour of the bay and discovered the glacier in 1879. It was soon found
that the bay could be safely navigated by vessels of large size, and from
that time on tourists in increasing number have been attracted to the
region. Commodious steamers now regularly run close up to the ice-front,
and lie-to for several hours, so that the passengers may witness the
"calving" of icebergs, and may climb upon the sides of the icy stream
and look into its deep crevasses and out upon its corrugated and broken
surface.
[Illustration: Fig. 12.--Map of Glacier Bay. Alaska, and its
surroundings. Arrow-points indicate glaciated area.]
The first persons who found it in their way to pay more than a tourist's
visit to this interesting object were Rev. J. L. Patton, Mr. Prentiss
Baldwin, and myself, who spent the entire month of August, 1886, encamped
at the foot of the glacier, conducting such observations upon it as
weather and equipment permitted. From that time till the summer of 1890
no one else stopped off from the tourist steamers to bestow any special
study upon it. But during this latter season Mr. Muir returned to the
scene of his discovered wonder, and spent some weeks in exploring the
interior of the great ice-field. During the same season, also, Professors
H. F. Reid and H. Cushing, with a well-equipped party of young men,
spent two months or more in the same field, conducting observations and
experiments, of various kinds, relating to the extent, the motion, and
the general behaviour of the vast mass of moving ice.
[Illustration: Fig. 13.--Shows central part of the front of Muir Glacier
one half mile distant. Near the lower left hand corner the ice is seen
one mile distant resting for about one half mile on gravel which it had
overrun. The ice is now retreating in the channel. (From photograph.)]
The main body of the Muir Glacier occupies a vast amphitheatre, with
diameters ranging from thirty to forty miles, and covers an area of about
one thousand square miles. From one of the low mountains near its mouth I
could count twenty-six tributary glaciers which came together and became
confluent in the main stream of ice. Nine medial moraines marked the
continued course of as many main branches, which becoming united formed
the grand trunk of the glacier. Numerous rocky eminences also projected
above the surface of the ice, like islands in the sea, corresponding to
what are called "_nunataks_" in Greenland. The force of the ice against
the upper side of these rocky prominences is such as to push it in great
masses above the surrounding level, after the analogy of waves which
dash themselves into foam against similar obstructions. In front of the
_nunataks_ there is uniformly a depression, like the eddies which appear
in the current below obstacles in running water.
Over some portions of the surface of the glacier there is a miniature
river system, consisting of a main stream, with numerous tributaries,
but all flowing in channels of deep blue ice. Before reaching the front
of the glacier, however, each one of these plunges down into a crevasse,
or _moulin_, to swell the larger current, which may be heard rushing
along in an impetuous course hundreds of feet beneath, and far out of
sight. The portion of the glacier in which there is the most rapid
motion is characterised by innumerable crags and domes and pinnacles of
ice, projecting above the general level, whose bases are separated by
fissures, extending in many cases more than a hundred feet below the
general level. These irregularities result from the combined effect
of the differential motion (as illustrated in the diagram on page 4),
and the influence of sunshine and warm air in irregularly melting the
unprotected masses. The description given in our introductory chapter of
medial moraines and ice-pillars is amply illustrated everywhere upon the
surface of the Muir Glacier. I measured one block of stone which was
twenty feet square and about the same height, standing on a pedestal of
ice three or four feet high.
The mountains forming the periphery of this amphitheatre rise to a height
of several thousand feet; Mount Fairweather, upon the northwest, from
whose flanks probably a portion of the ice comes, being, in fact, more
than fifteen thousand feet high. The mouth of the amphitheatre is three
miles wide, in a line extending from shoulder to shoulder of the low
mountains which guard it. The actual water-front where the ice meets
tide-water is one mile and a half.[AI] Here the depth of the inlet is so
great that the front of the ice breaks off in icebergs of large size,
which float away to be dissolved at their leisure. At the water's edge
the ice presents a perpendicular front of from two hundred and fifty to
four hundred feet in height, and the depth of the water in the middle of
the inlet immediately in front of the ice is upwards of seven hundred
feet; thus giving a total height to the precipitous front of a thousand
feet.
[Footnote AI: These are the measurements of Professor Reid. In my former
volume I have given the dimensions as somewhat smaller.]
The formation of icebergs can here be studied to admirable advantage.
During the month in which we encamped in the vicinity the process
was going on continuously. There was scarcely an interval of fifteen
minutes during the whole time in which the air was not rent with the
significant boom connected with the "calving" of a berg. Sometimes this
was occasioned by the separation of a comparatively small mass of ice
from near the top of the precipitous wall, which would fall into the
water below with a loud splash. At other times I have seen a column of
ice from top to bottom of the precipice split off and fall over into the
water, giving rise to great waves, which would lash the shore with foam
two miles below.
This manner of the production of icebergs differs from that which has
been ordinarily represented in the text-books, but it conforms to the law
of glacial motion, which we will describe a little later, namely, that
the upper strata of ice move faster than the lower. Hence the tendency
is constantly to push the upper strata forwards, so as to produce
a perpendicular or even projecting front, after the analogy of the
formation of breakers on the shelving shore of a large body of water.
Evidently, however, these masses of ice which break off from above the
water do not reach the whole distance to the bottom of the glacier below
the water; so that a projecting foot of ice remains extending to an
indefinite distance underneath the surface. But at occasional intervals,
as the superincumbent masses of ice above the surface fall off and
relieve the strata below of their weight, these submerged masses suddenly
rise, often shooting up considerably higher than they ultimately remain
when coming to rest. The bergs formed by this latter process often bear
much earthy material upon them, which is carried away with the floating
ice, to be deposited finally wherever the melting chances to take place.
Numerous opportunities are furnished about the front and foot of
this vast glacier to observe the manner of the formation of _kames_,
kettle-holes, and various other irregular forms into which glacial
_débris_ is accustomed to accumulate. Over portions of the decaying
foot of the glacier, which was deeply covered with morainic _débris_,
the supporting ice is being gradually removed through the influence of
subglacial streams or of abandoned tunnels, which permit the air to exert
its melting power underneath. In some places where old _moulins_ had
existed, the supporting ice is melting away, so that the superincumbent
mass of sand, gravel, and boulders is slowly sliding into a common
centre, like grain in a hopper. This must produce a conical hill, to
remain, after the ice has all melted away, a mute witness of the
impressive and complicated forces which have been so long in operation
for its production.
In other places I have witnessed the formation of a long ridge of gravel
by the gradual falling in of the roof of a tunnel which had been occupied
by a subglacial stream, and over which there was deposited a great amount
of morainic material. As the roof gave way, this was constantly falling
to the bottom, where, being exempt from further erosive agencies, it must
remain as a gravel ridge or kame.
In other places, still, there were vast masses of ice covering many
acres, and buried beneath a great depth of morainic material which had
been swept down upon it while joined to the main glacier. In the retreat
of the ice, however, these masses had become isolated, and the sand,
gravel, and boulders were sliding down the wasting sides and forming long
ridges of _débris_ along the bottom, which, upon the final melting of
the ice, will be left as a complicated network of ridges and knolls of
gravel, enclosing an equally complicated nest of kettle-holes.
Beyond Cross Sound the Pacific coast is bounded for several hundred
miles by the magnificent semicircle of mountains known as the St. Elias
Alps, with Mount Crillon at the south, having an elevation of nearly
sixteen thousand feet, and St. Elias in the centre, rising to a greater
height. Everywhere along this coast, as far as the Alaskan Peninsula,
vast glaciers come down from the mountain-sides, and in many cases their
precipitous fronts form the shore-line for many miles at a time. Icy
Bay, just to the south of Mount St, Elias, is fitly named, on account of
the extent of the glaciers emptying into it and the number of icebergs
cumbering its waters.
In the summer of 1890 a party, under the lead of Mr. I. C. Russell, of
the United States Geological Survey, made an unsuccessful attempt to
scale the heights of Mount St. Elias; but the information brought back
by them concerning the glaciers of the region amply repaid them for their
toil and expense, and consoled them for the failure of their immediate
object.
[Illustration: Fig. 14.--By the courtesy of the National Geographical
Society.]
Leaving Yakutat Bay, and following the route indicated upon the
accompanying map, they travelled on glacial ice almost the entire
distance to the foot of Mount St. Elias. The numerous glaciers coming
down from the summit of the mountain-ridge become confluent nearer the
shore, and spread out over an area of about a thousand square miles. This
is fitly named the Malaspina Glacier, after the Spanish explorer who
discovered it in 1792.
It is not necessary to add further particulars concerning the results
of this expedition, since they are so similar to those already detailed
in connection with the Muir Glacier. A feature, however, of special
interest, pertains to the glacial lakes which are held in place by the
glacial ice at an elevation of thousands of feet above the sea. One of
considerable size is indicated upon the map just south of what was called
Blossom Island, which, however, is not an island, but simply a _nunatak_,
the ice here surrounding a considerable area of fertile land, which is
covered with dense forests and beautified by a brilliant assemblage of
flowering plants. In other places considerable vegetation was found upon
the surface of moraines, which were probably still in motion with the
underlying ice.
_Greenland._--The continental proportions of Greenland, and the extent
to which its area is covered by glacial ice, make it by far the most
important accessible field for glacial observations. The total area of
Greenland can not be less than five hundred thousand square miles--equal
in extent to the portion of the United States east of the Mississippi
and north of the Ohio. It is now pretty evident that the whole of this
area, except a narrow border about the southern end, is covered by one
continuous sheet of moving ice, pressing outward on every side towards
the open water of the surrounding seas.
For a long time it was the belief of many that a large region in the
interior of Greenland was free from ice, and was perhaps inhabited.
It was in part to solve this problem that Baron Nordenskiöld set out
upon his expedition of 1883. Ascending the ice-sheet from Disco Bay, in
latitude 69°, he proceeded eastward for eighteen days across a continuous
ice-field. Rivers were flowing in channels upon the surface like those
cut on land in horizontal strata of shale or sandstone, only that the
pure deep blue of the ice-walls was, by comparison, infinitely more
beautiful. These rivers were not, however, perfectly continuous. After
flowing for a distance in channels on the surface, they, one and all,
plunged with deafening roar into some yawning crevasse, to find their way
to the sea through subglacial channels. Numerous lakes with shores of ice
were also encountered.
[Illustration: Fig. 15.--Map of Greenland. The arrow-points mark the
margin of the ice-field.]
"On bending down the ear to the ice," says this explorer, "we could hear
on every side a peculiar subterranean hum, proceeding from rivers flowing
within the ice; and occasionally a loud, single report, like that of a
cannon, gave notice of the formation of a new glacier-cleft.... In the
afternoon we saw at some distance from us a well-defined pillar of mist,
which, when we approached it, appeared to rise from a bottomless abyss,
into which a mighty glacier-river fell. The vast, roaring water-mass had
bored for itself a vertical hole, probably down to the rock, certainly
more than two thousand feet beneath, on which the glacier rested."[AJ]
[Footnote AJ: Geological Magazine, vol. ix, pp. 393, 399.]
At the end of the eighteen days Nordenskiöld found himself about a
hundred and fifty miles from his starting-point, and about five thousand
feet above the sea. Here the party rested, and sent two Eskimos forward
on _skidor_--a kind of long wooden skate, with which they could move
rapidly over the ice, notwithstanding the numerous small, circular holes
which everywhere pitted the surface. These Eskimos were gone fifty-seven
hours, having slept only four hours of the period. It is estimated that
they made about a hundred and fifty miles, and attained an altitude of
six thousand feet. The ice is reported as rising in distinct terraces,
and as seemingly boundless beyond. If this is the case, two hundred miles
from Disco Bay, there would seem little hope of finding in Greenland
an interior freed from ice. So we may pretty confidently speak of that
continental body of land as still enveloped in an ice-sheet. Up to about
latitude 75°, however, the continent is fringed by a border of islands,
over which there is no continuous covering of ice. In south Greenland
the continuous ice-sheet is reached about thirty miles back from the
shore.
A summary of the results of Greenland exploration was given by Dr. Kink
in 1886, from which it appears that since 1876 one thousand miles of
the coast-line have been carefully explored by entering every fiord and
attempting to reach the inland ice. According to this authority--
We are now able to demonstrate that a movement of ice from the central
regions of Greenland to the coast continually goes on, and must be
supposed to act upon the ground over which it is pushed so as to detach
and transport fragments of it for such a distance.... The plainest idea
of the ice-formation here in question is given by comparing it with an
inundation.... Only the marginal parts show irregularity; towards the
interior the surface grows more and more level and passes into a plain
very slightly rising in the same direction. It has been proved that,
ascending its extreme verge, where it has spread like a lava-stream over
the lower ground in front of it, the irregularities are chiefly met with
up to a height of 2,000 feet, but the distance from the margin in which
the height is reached varies much. While under 68-1/2° north latitude it
took twenty-four miles before this elevation was attained, in 72-1/2° the
same height was arrived at in half the distance....
A general movement of the whole mass from the central regions towards the
sea is still continued, but it concentrates its force to comparatively
few points in the most extraordinary degree. These points are represented
by the ice-fiords, through which the annual surplus ice is carried off
in the shape of bergs.... In Danish Greenland are found five of the
first, four of the second, and eight of the third (or least productive)
class, besides a number of inlets which only receive insignificant
fragments. Direct measurements of the velocity have now been applied on
three first-rate and one second-rate fiords, all situated between 69°
and 71° north latitude. The measurements have been repeated during the
coldest and the warmest season, and connected with surveying and other
investigations of the inlets and their environs. It is now proved that
the glacier branches which produce the bergs proceed incessantly at a
rate of thirty to fifty feet per diem, this movement being not at all
influenced by the seasons. . . .
In the ice-fiord of Jakobshavn, which spreads its enormous bergs over
Disco Bay and probably far into the Atlantic, the productive part of the
glacier is 4,500 metres (about 2-1/2 miles) broad. The movement along its
middle line, which is quicker than on the sides nearer the shores, can
be rated at fifty feet per diem. The bulk of ice here annually forced
into the sea would, if taken on the shore, make a mountain two miles
long, two miles broad, and 1,000 feet high. The ice-fiord of Torsukatak
receives four or five branches of the glacier; the most productive of
them is about 9,000 metres broad (five miles), and moves between sixteen
and thirty-two feet per diem. The large Karajak Glacier, about 7,000
metres (four miles) broad, proceeds at a rate of from twenty-two to
thirty-eight feet per diem. Finally, a glacier branch dipping into the
fiord of Jtivdliarsuk, 5,800 metres broad (three miles), moved between
twenty-four and forty-six feet per diem.[AK]
[Footnote AK: See Transactions of the Edinburgh Geological Society for
February 18, 1886, vol. v, part ii, pp. 286-293.]
The principal part of our information concerning the glaciers of
Greenland north of Melville Bay was obtained by Drs. Kane and Hayes,
in 1853 and 1854, while conducting an expedition in search of Sir
John Franklin and his unfortunate crew. Dr. Hayes conducted another
expedition to the same desolate region in 1860, while other explorers
have to some extent supplemented their observations. The largest glacier
which they saw enters the sea between latitude 79° and 80°, where it
presents a precipitous discharging front more than sixty miles in width
and hundreds of feet in perpendicular height.
Dr. Kane gives his first impressions of this grand glacier in the
following vivid description:
"I will not attempt to do better by florid description. Men only
rhapsodize about Niagara and the ocean. My notes speak simply of the
'long, ever-shining line of cliff diminished to a well-pointed wedge in
the perspective'; and, again, of 'the face of glistening ice, sweeping
in a long curve from the low interior, the facets in front intensely
illuminated by the sun.' But this line of cliff rose in a solid,
glassy wall three hundred feet above the water-level, with an unknown,
unfathomable depth below it; and its curved face, sixty miles in length
from Cape Agassiz to Cape Forbes, vanished into unknown space at not more
than a single day's railroad-travel from the pole. The interior, with
which it communicated and from which it issued, was an unsurveyed _mer de
glace_--an ice-ocean to the eye, of boundless dimensions.
"It was in full sight--the mighty crystal bridge which connects the two
continents of America and Greenland. I say continents, for Greenland,
however insulated it may ultimately prove to be, is in mass strictly
continental. Its least possible axis, measured from Cape Farewell to the
line of this glacier, in the neighbourhood of the eightieth parallel,
gives a length of more than 1,200 miles, not materially less than that of
Australia from its northern to its southern cape.
"Imagine, now, the centre of such a continent, occupied through nearly
its whole extent by a deep, unbroken sea of ice that gathers perennial
increase from the water-shed of vast snow-covered mountains and all the
precipitations of its atmosphere upon its own surface. Imagine this,
moving onwards like a great glacial river, seeking outlets at every fiord
and valley, rolling icy cataracts into the Atlantic and Greenland seas;
and, having at last reached the northern limit of the land that has borne
it up, pouring out a mighty frozen torrent into unknown arctic space!
"It is thus, and only thus, that we must form a just conception of a
phenomenon like this great glacier. I had looked in my own mind for such
an appearance, should I ever be fortunate enough to reach the northern
coast of Greenland; but, now that it was before me, I could hardly
realize it. I had recognized, in my quiet library at home, the beautiful
analogies which Forbes and Studer have developed between the glacier and
the river. But I could not comprehend at first this complete substitution
of ice for water.
"It was slowly that the conviction dawned on me that I was looking upon
the counterpart of the great river-system of Arctic Asia and America. Yet
here were no water-feeders from the south. Every particle of moisture had
its origin within the polar circle and had been converted into ice. There
were no vast alluvions, no forest or animal traces borne down by liquid
torrents. Here was a plastic, moving, semi-solid mass, obliterating life,
swallowing rocks and islands, and ploughing its way with irresistible
march through the crust of an investing sea."[AL]
[Footnote AL: Arctic Explorations in the Years 1853, 1854, and 1855, vol.
i, pp. 225-228.]
Much less is known concerning the eastern coast of Greenland than
about the western coast. For a long time it was supposed that there
might be a considerable population in the lower latitudes along the
eastern side. But that is now proved to be a mistake. The whole coast
is very inhospitable and difficult of approach. From latitude 65° to
latitude 69° little or nothing is known of it. In 1822-'23 Scoresby,
Cleavering, and Sabine hastily explored the coast from latitude 69° to
76°, and reported numerous glaciers descending to the sea-level through
extensive fiords, from which immense icebergs float out and render
navigation dangerous. In 1869 and 1870 the second North-German Expedition
partly explored the coast between latitude 73° and 77°. Mr. Payer, an
experienced Alpine explorer, who accompanied the expedition, reports the
country as much broken, and the glaciers as "subordinated in position to
the higher peaks, and having their moraines, both lateral and terminal,
like those of the Alpine ranges, and on a still grander scale." Petermann
Peak, in latitude 73°, is reported as 13,000 feet high. Captain Koldewey,
chief of the expedition, found extensive plateaus on the mainland, in
latitude 75°, to be "entirely clear of snow, although only sparsely
covered with vegetation." The mountains in this vicinity, also, rising to
a height of more than 2,000 feet, were free from snow in the summer. Some
of the fiords in this vicinity penetrate the continent through several
degrees of longitude.
An interesting episode of this expedition was the experience of the crew
of the ship Hansa, which was caught in the ice and destroyed. The crew,
however, escaped by encamping on the ice-floe which had crushed the ship.
From this, as it slowly floated towards the south through several degrees
of latitude, they had opportunity to make many important observations
upon the continent itself. As viewed from this unique position the coast
had the appearance everywhere of being precipitous, with mountains of
considerable height rising in the background, from which numerous small
glaciers descended to the sea-level.
In 1888 Dr. F. Nansen, with Lieutenant Sverdrup and four others, was
left by a whaler on the ice-pack bordering the east of Greenland about
latitude 65°, and in sight of the coast. For twelve days the party was
on the ice-pack floating south, and so actually reached the coast only
about latitude 64°. From this point they attempted to cross the inland
ice in a northwesterly direction towards Christianshaab. They soon
reached a height of 7,000 feet, and were compelled by severe northerly
storms to diverge from their course, taking a direction more to the west.
The greatest height attained was 9,500 feet, and the party arrived on the
western coast at Ameralik Fiord, a little south of Godhaab, about the
same latitude at which they entered.
It thus appears that subsequent investigations have confirmed in a
remarkable manner the sagacious conclusions made by the eminent Scotch
geologist and glacialist Robert Brown in 1875, soon after his own
expedition to the country. "I look upon Greenland and its interior
ice-field," he writes, "in the light of a broad-lipped, shallow vessel,
but with chinks in the lips here and there, and the glacier like viscous
matter in it. As more is poured in, the viscous matter will run over the
edges, naturally taking the line of the chinks as its line of outflow.
The broad lips of the vessel are the outlying islands or 'outskirts';
the viscous matter in the vessel the inland ice, the additional matter
continually being poured in in the form of the enormous snow covering,
which, winter after winter, for seven or eight months in the year, falls
almost continuously on it; the chinks are the fiords or valleys down
which the glaciers, representing the outflowing viscous matter, empty the
surplus of the vessel--in other words, the ice floats out in glaciers,
overflows the land in fact, down the valleys and fiords of Greenland
by force of the superincumbent weight of snow, just as does the grain
on the floor of a barn (as admirably described by Mr. Jamieson) when
another sackful is emptied on the top of the mound already on the floor.
'The floor is flat, and therefore does not conduct the grain in any
direction; the outward motion is due to the pressure of the particles
of grain on one another; and, given a floor of infinite extension and a
pile of sufficient amount, the mass would move outward to any distance,
and with a very slight pitch or slope it would slide forward along the
incline.' To this let me add that if the floor on the margin of the heap
of grain was undulating the stream of grain would take the course of
such undulations. The want, therefore, of much slope in a country and
the absence of any great mountain-range are of very little moment to the
movement of land-ice, _provided we have snow enough_" On another page Dr.
Brown had well said that "the country seems only a circlet of islands
separated from one another by deep fiords or straits, and bound together
on the landward side by the great ice covering which overlies the whole
interior.... No doubt under this ice there lies land, just as it lies
under the sea; but nowadays none can be seen, and as an insulating medium
it might as well be water."
In his recently published volumes descriptive of the journey across
the Greenland ice-sheet, alluded to on page 39, Dr. Nansen sums up his
inferences in very much the same way: "The ice-sheet rises comparatively
abruptly from the sea on both sides, but more especially on the east
coast, while its central portion is tolerably flat. On the whole, the
gradient decreases the farther one gets into the interior, and the mass
thus presents the form of a shield with a surface corrugated by gentle,
almost imperceptible, undulations lying more or less north and south,
and with its highest point not placed symmetrically, but very decidedly
nearer the east coast than the west."
From this rapid glance at the existing glaciers of the world we see that
a great ice age is not altogether a strange thing in the world. The lands
about the south pole and Greenland are each continental in dimensions,
and present at the present time accumulations of land-ice so extensive,
so deep, and so alive with motion as to prepare our minds for almost
anything that may be suggested concerning the glaciated condition of
other portions of the earth's surface. The _vera causa_ is sufficient
to accomplish anything of which glacialists have ever dreamed. It only
remains to enquire what the facts really are and over how great an extent
of territory the actual results of glacial action may be found. But we
will first direct more particular attention to some of the facts and
theories concerning glacial motion.