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OF the small residual
glaciers mentioned in the preceding chapter, I have found sixty-five in that
portion of the range lying between latitude 36° 30' and 39°. They occur
singly or in small groups on the north sides of the peaks of the High
Sierra, sheltered beneath broad frosty shadows, in amphitheaters of their
own making, where the snow, shooting down from the surrounding heights in
avalanches, is most abundant. Over two thirds of the entire number lie
between latitude 37° and 38°, and form the highest fountains of the San
Joaquin, Merced, Tuolumne, and Owen's Rivers.
The glaciers of Switzerland,
like those of the Sierra, are mere wasting remnants of mighty ice floods
that once filled the great valleys and poured into the sea. So, also, are
those of Norway, Asia, and South America. Even the grand continuous mantles
of ice that still cover Greenland, Spitzbergen, Nova Zembla,
Franz-Joseph-Land, parts of Alaska, and the south polar region are
shallowing and shrinking. Every glacier in the world is smaller than it once
was. All the world is growing warmer, or the crop of snow-flowers is
diminishing. But in contemplating the condition of the glaciers of the
world, we must bear in mind while trying to account for the changes going on
that the same sunshine that wastes them builds them. Every glacier records
the expenditure of an enormous amount of sun-heat in lifting the vapor for
the snow of which it is made from the ocean to the mountains, as Tyndall
strikingly shows.
The number of glaciers in the
Alps, according to the Schlagintweit brothers, is eleven hundred, of which
one hundred may be regarded as primary, and the total area of ice, snow, and
neve is estimated at 1177 square miles, or an average for each glacier of
little more than one square mile. On the same authority, the average height
above sea-level at which they melt is about 7414 feet. The Grindelwald
Glacier descends below four thousand feet, and one of the Mont Blanc
glaciers reaches nearly as low a point. One of the largest of the Himalaya
glaciers on the head waters of the Ganges does not, according to Captain
Hodgson, descend below 12,914 feet. The largest of the Sierra glaciers on
Mount Shasta descends to within ninety-five hundred feet of the level of the
sea, which, as far as I have observed, is the lowest point reached by any
glacier within the bounds of California, the average height of all being not
far from eleven thousand feet.
The changes that have taken
place in the glacial conditions of the Sierra from the time of greatest
extension is well illustrated by the series of glaciers of every size and
form extending along the mountains of the coast to Alaska. A general
exploration of this instructive region shows that to the north of
California, through Oregon and Washington, groups of active glaciers still
exist on all the high volcanic cones of the Cascade Range, — Mount Pitt, the
Three Sisters, Mounts Jefferson, Hood, St. Helens, Adams, Rainier, Baker,
and others, — some of them of considerable size, though none of them
approach the sea. Of these mountains Rainier, in Washington, is the highest
and iciest. Its dome-like summit, between fourteen and fifteen thousand feet
high, is capped with ice, and eight glaciers, seven to twelve miles long,
radiate from it as a center, and form the sources of the principal streams
of the State. The lowest-descending of this fine group flows through
beautiful forests to within thirty-five hundred feet of the sea-level, and
sends forth a river laden with glacier mud and sand. On through British
Columbia and southeastern Alaska the broad, sustained mountain-chain,
extending along the coast, is generally glacier-bearing. The upper branches
of nearly all the main canons and fiords are occupied by glaciers, which
gradually increase in size, and descend lower until the high region between
Mount Fairweather and Mount St. Elias is reached, where a considerable
number discharge into the waters of the ocean. This is preeminently the ice
land of Alaska and of the entire Pacific Coast.
Northward from here the
glaciers gradually diminish in size and thickness, and melt at higher
levels. In Prince William Sound and Cook's Inlet many fine glaciers are
displayed, pouring from the surrounding mountains; but to the north of
latitude 62° few, if any, glaciers remain, the ground being mostly low and
the snowfall light. Between latitude 56° and 600 there are probably more
than five thousand glaciers, not counting the smallest. Hundreds of the
largest size descend through the forests to the level of the sea, or near
it, though as far as my own observations have reached, after a pretty
thorough examination of the region, not more than twenty-five discharge
icebergs into the sea. All the long high-walled fiords into which these
great glaciers of the first class flow are of course crowded with icebergs
of every conceivable form, which are detached with thundering noise at
intervals of a few minutes from an imposing ice wall that is thrust forward
into deep water. But these Pacific Coast icebergs are small as compared with
those of Greenland and the Antarctic region, and only a few of them escape
from the intricate system of channels, with which this portion of the coast
is fringed, into the open sea. Nearly all of them are swashed and drifted by
wind and tide back and forth in the fiords until finally melted by the ocean
water, the sunshine, the warm winds, and the copious rains of summer. Only
one glacier on the coast, observed by Professor Russell, discharges its
bergs directly into the open sea, at Icy Cape, opposite Mount St. Elias. The
southernmost of the glaciers that reach the sea occupies a narrow,
picturesque fiord about twenty miles to the northwest of the mouth of the
Stickeen River, in latitude 56° 50'. The fiord is called by the natives "Hutli,"
or Thunder Bay, from the noise made by the discharge of the icebergs. About
one degree farther north there are four of these complete glaciers,
discharging at the heads of the long arms of Holkam Bay. At the head of the
Tahkoo Inlet, still farther north, there is one; and at the head and around
the sides of Glacier Bay, trending in a general northerly direction from
Cross Sound in latitude 58° to 59°, there are seven of these complete
glaciers pouring bergs into the bay and its branches, and keeping up an
eternal thundering. The largest of this group, the Muir, has upward of two
hundred tributaries, and a width below the confluence of the main
tributaries of about twenty-five miles. Between the west side of this icy
bay and the ocean all the ground, high and low, excepting the peaks of the
Fairweather Range, is covered with a mantle of ice from one thousand to
probably three thousand feet thick, which discharges by many distinct
mouths.
This fragmentary ice sheet,
and the immense glaciers about Mount St. Elias, together with the multitude
of separate river-like glaciers that load the slopes of the coast mountains,
ev ideijtly once formed part of a continuous ice sheet that flowed over all
the region hereabouts and only a comparatively short time ago extended as
far southward as the mouth of the Strait of Juan de Fuca, probably farther.
All the islands of the Alexander Archipelago, as well as the headlands and
promontories of the mainland, display telling traces of this great mantle
that are still fresh and unmistakable. They all have the forms of the
greatest strength with reference to the action of a vast rigid press of
oversweeping ice from the north and northwest, and their surfaces have a
smooth, rounded, overrubbed appearance, generally free from angles. The
intricate labyrinth of canals, channels, straits, passages, sounds, narrows,
etc., between the islands, and extending into the mainland, of course
manifest in their forms and trends and general characteristics the same
subordination to the grinding action of universal glaciation as to their
origin, and differ from the islands and banks of the fiords only in being
portions of the pre-glacial margin of the continent more deeply eroded, and
therefore covered by the ocean waters which flowed into them as the ice was
melted out of them. The formation and extension of fiords in this manner is
still going on, and may be witnessed in many places in Glacier Bay, Yakutat
Bay, and adjacent regions. That the domain of the sea is being extended over
the land by the wearing away of its shores, is well known, but in these icy
regions of Alaska, and even as far south as Vancouver Island, the coast
rocks have been so short a time exposed to wave action they are but little
wasted as yet. In these regions the extension of the sea effected by its own
action in post-glacial time is scarcely appreciable as compared with that
effected by ice action.
Traces of the vanished
glaciers made during the period of greater extension abound on the Sierra as
far south as latitude 36°. Even the polished rock surfaces, the most
evanescent of glacial records, are still found in a wonderfully perfect
state of preservation on the upper half of the middle portion of the range,
and form the most striking of all the glacial phenomena. They occur in large
irregular patches in the summit and middle regions, and though they have
been subjected to the action of the weather with its corroding storms for
thousands of years, their mechanical excellence is such that they still
reflect the sunbeams like glass, and attract the attention of every
observer. The attention of the mountaineer is seldom arrested by moraines,
however regular and high they may be, or by canons, however deep, or by
rocks, however noble in form and sculpture; but he stoops and rubs his hands
admiringly on the shining surfaces and tries hard to account fQr their
mysterious smoothness. He has seen the snow descending in avalanches, but
concludes this cannot be the work of snow, for he finds it where no
avalanches occur. Nor can water have done it, for he sees this smoothness
glowing on the sides and tops of the highest domes. Only the winds of all
the agents he knows seem capable of flowing in the directions indicated by
the scoring. Indians, usually so little curious about geological phenomena,
have come to me occasionally and asked me, "What makeum the ground so smooth
at Lake Tenaya?" Even horses and dogs gaze wonderingly at the strange
brightness of the ground, and smell the polished spaces and place their feet
cautiously on them when they come to them for the first time, as if afraid
of sinking. The most perfect of the polished pavements and walls lie at an
elevation of from seven to nine thousand feet above the sea, where the rock
is compact silicious granite. Small dim patches may be found as low as three
thousand feet on the driest and most enduring portions of sheer walls with a
southern exposure, and on compact swelling bosses partially protected from
rain by a covering of large boulders. On the north half of the range the
striated and polished surfaces are less common, not only because this part
of the chain is lower, but because the surface rocks are chiefly porous
lavas subject to comparatively rapid waste. The ancient moraines also,
though well preserved on most of the south half of the range, are nearly
obliterated to the northward, but their material is found scattered and
disintegrated.
A similar blurred condition
of the superficial records of glacial action obtains throughout most of
Oregon, Washington, British Columbia and Alaska, due in great part to the
action of excessive moisture. Even in southeastern Alaska, where the most
extensive glaciers on the continent are, the more evanescent of the traces
of their former greater extension, though comparatively recent, are more
obscure than those of the ancient California glaciers where the climate is
drier and the rocks more resisting.
These general views of the
glaciers of the Pacific Coast will enable my readers to see something of the
changes that have taken place in California, and will throw light on the
residual glaciers of the High Sierra.
Prior to the autumn of 1871
the glaciers of the Sierra were unknown. In October of that year I
discovered the Black Mountain Glacier in a shadowy amphitheater between
Black and Red Mountains, two of the peaks of the Merced group. This group is
the highest portion of a spur that straggles out from the main axis of the
range in the direction of Yosemite Valley. At the time of this interesting
discovery I was exploring the neve amphitheaters of the group, and tracing
the courses of the ancient glaciers that once poured from its ample
fountains through the Illilouette Basin and the Yosemite Valley, not
expecting to find any active glaciers so far south in the land of sunshine.
Beginning on the northwestern
extremity of the group, I explored the chief tributary basins in succession,
their moraines, roches moutonnees, and splendid glacier pavements, taking
them in regular succession without any reference to the time consumed in
their study. The monuments of the tributary that poured its ice from between
Red and Black Mountains I found to be the most interesting of them all; and
when I saw its magnificent moraines extending in majestic curves from the
spacious amphitheater between the mountains, I was exhilarated with the work
that lay before me. It was one of the golden days of the Sierra Indian
summer, when the rich sunshine glorifies every landscape however rocky and
cold, and suggests anything rather than glaciers. The path of the vanished
glacier was warm now, and shone in many places as if washed with silver. The
tall pines growing on the moraines stood transfigured in the glowing light,
the poplar groves on the levels of the basin were masses of orange-yellow,
and the late-blooming goldenrods added gold to gold. Pushing on over my rosy
glacial highway, I passed lake after lake set in solid basins of granite,
and many a thicket and meadow watered by a stream that issues from the
amphitheater and links the lakes together; now wading through plushy bogs
knee-deep in yellow and purple sphagnum; now passing over bare rock. The
main lateral moraines that bounded the view on either hand are from one
hundred to nearly two hundred feet high, and about as regular as artificial
embankments, and covered with a superb growth of silver fir and pine. But
this garden and forest luxuriance was speedily left behind. The trees were
dwarfed as I ascended; patches of the alpine bryanthus and cassiope began to
appear, and arctic willows pressed into flat carpets by the winter snow. The
lakelets, which a few miles down the valley were so richly embroidered with
flowery meadows, had here, at an elevation of ten thousand feet, only small
brown mats of carex, leaving bare rocks around more than half their shores.
Yet amid this alpine suppression the mountain pine bravely tossed his
storm-beaten branches on the ledges and buttresses of Red Mountain, some
specimens being over one hundred feet high, and twenty-four feet in
circumference, and seemingly as fresh and vigorous as the giants of the
lower zones.
Evening came on just as I got
fairly within the portal of the main amphitheater. It is about a mile wide,
and a little less than two miles long. The crumbling spurs and battlements
of Red Mountain bound it on the north, the somber, rudely sculptured
precipices of Black Mountain on the south, and a hacked, splintery col,
curving around from mountain to mountain, shuts it in on the east.
I chose a camping-ground on
the brink of one of the lakes where a thicket of hemlock spruce sheltered me
from the night wind. Then, after making a tin-cupful of tea, I sat by my
camp-fire reflecting on the grandeur and significance of the glacial records
I had seen. As the night advanced the mighty rock walls of my mountain
mansion seemed to come nearer, while the starry sky in glorious brightness
stretched across like a ceiling from wall to wall, and fitted closely down
into all the spiky irregularities of the summits. Then, after a long
fireside rest and a glance at my notebook, I cut a few leafy branches for a
bed, and fell into the clear, death-like sleep of the tired mountaineer.
Early next morning I set out
to trace the grand old glacier that had done so much for the beauty of the
Yosemite region back to its farthest fountains, enjoying the charm that
every explorer feels in Nature's untrodden wildernesses. The voices of the
mountains were still asleep. The wind scarce stirred the pine needles. The
sun was up, but it was yet too cold for the birds and the few burrowing
animals that dwell here. Only the stream, cascading from pool to pool,
seemed to be wholly awake. Yet the spirit of the opening day called to
action. The sunbeams came streaming gloriously through the jagged openings
of the col, glancing on the burnished pavements and lighting the silvery
lakes, while every sun-touched rock burned white on its edges like melting
iron in a furnace. Passing round the north shore of my camp lake I followed
the central stream past many cascades from lakelet to lakelet. The scenery
became more rigidly arctic, the dwarf pines and hemlocks disappeared, and
the stream was bordered with icicles. As the sun rose higher rocks were
loosened on shattered portions of the cliffs, and came down in rattling
avalanches, echoing wildly from crag to crag.
The main lateral moraines
that extend from the jaws of the amphitheater into the Illilouette Basin are
continued in straggling masses along the walls of the amphitheater, while
separate boulders, hundreds of tons in weight, are left stranded here and
there out in the middle of the channel. Here, also, I observed a series of
small terminal moraines ranged along the south wall of the amphitheater,
corresponding in size and form with the shadows cast by the highest
portions. The meaning of this correspondence between moraines and shadows
was afterward made plain. Tracing the stream back to the last of its chain
of lakelets, I noticed a deposit of fine gray mud on the bottom except where
the force of the entering current had prevented its settling. It looked like
the mud worn from a grindstone, and I at once suspected its glacial origin,
for the stream that was carrying it came gurgling out of the base of a raw
moraine that seemed in process of formation. Not a plant or weather-stain
was visible on its rough, unsettled surface. It is from sixty to over one
hundred feet high, and plunges forward at an angle of thirty-eight degrees.
Cautiously picking my way, I gained the top of the moraine and was delighted
to see a small but well-characterized glacier swooping down from the gloomy
precipices of Black Mountain in a finely graduated curve to the moraine on
which I stood. The compact ice appeared on all the lower portions of the
glacier, though gray with dirt and stones embedded in it. Farther up the ice
disappeared beneath coarse granulated snow. The surface of the glacier was
further characterized by dirt bands and the outcropping edges of the blue
veins, showing the laminated structure of the ice. The uppermost crevasse,
or "bergschrund," where the neve was attached to the mountain, was from
twelve to fourteen feet wide, and was bridged in a few places by the remains
of snow avalanches. Creeping along the edge of the schrund, holding on with
benumbed fingers, I discovered clear sections where the bedded structure was
beautifully revealed. The surface snow, though sprinkled with stones shot
down from the cliffs, was in some places almost pure, gradually becoming
crystalline and changing to whitish porous ice of different shades of color,
and this again changing at a depth of twenty or thirty feet to blue ice,
some of the ribbon-like bands of which were nearly pure, and blended with
the paler bands in the most gradual and delicate manner imaginable. A series
of rugged zigzags enabled me to make my way down into the weird underworld
of the crevasse. Its chambered hollows were hung with a multitude of
clustered icicles, amid which pale, subdued light pulsed and shimmered with
indescribable loveliness. Water dripped and tinkled overhead, and from far
below came strange, solemn murmurings from currents that were feeling their
way through veins and fissures in the dark. The chambers of a glacier are
perfectly enchanting, notwithstanding one feels out of place in their frosty
beauty. I was soon cold in my shirt-sleeves, and the leaning wall threatened
to engulf me; yet it was hard to leave the delicious music of the water and
the lovely light. Coming again to the surface, I noticed boulders of every
size on their journeys to the terminal moraine — journeys of more than a
hundred years, without a single stop, night or day, winter or summer.
The sun gave birth to a
network of sweet-voiced rills that ran gracefully down the glacier, curling
and swirling in their shining channels, and cutting clear sections through
the porous surface-ice into the solid blue, where the structure of the
glacier was beautifully illustrated.
The series of small terminal
moraines which I had observed in the morning, along the south wall of the
amphitheater, correspond in every way with the moraine of this glacier, and
their distribution with reference to shadows was now understood. When the
climatic changes came on that caused the melting and retreat of the main
glacier that filled the amphitheater, a series of residual glaciers were
left in the cliff shadows, under the protection of which they lingered,
until they formed the moraines we are studying. Then, as the snow became
still less abundant, all of them vanished in succession, except the one just
described; and the cause of its longer life is sufficiently apparent in the
greater area of snow-basin it drains, and its more perfect protection from
wasting sunshine. How much longer this little glacier will last depends, of
course, on the amount of snow it receives from year to year, as compared
with melting waste.
After this discovery, I made
excursions over all the High Sierra, pushing my explorations summer after
summer, and discovered that what at first sight in the distance looked like
extensive snowfields, were in great part glaciers, busily at work completing
the sculpture of the summit-peaks so grandly blocked out by their giant
predecessors.
On August 21, I set a series
of stakes in the Maclure Glacier, near Mount Lyell, and found its rate of
motion to be little more than an inch a day in the middle, showing a great
contrast to the Muir Glacier in Alaska, which, near the front, flows at a
rate of from five to ten feet in twenty-four hours.
Mount Shasta has three
glaciers, but Mount Whitney, although it is the highest mountain in the
range, does not now cherish a single glacier. Small patches of lasting snow
and ice occur on its northern slopes, but they are shallow, and present no
well marked evidence of glacial motion. Its sides, however, are scored and
polished in many places by the action of its ancient glaciers that flowed
east and west as tributaries of the great glaciers that once filled the
valleys of the Kern and Owen's Rivers. |
