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THE first snow that whitens
the Sierra usually falls about the end of October or early in November, to a
depth of a few inches, after months of the most charming Indian summer
weather imaginable. But in a few days, this light covering mostly melts from
the slopes exposed to the sun and causes but little apprehension on the part
of mountaineers who may be lingering among the high peaks at this time. The
first general winter storm that yields now that is to form a lasting portion
of the season's supply, seldom breaks on the mountains before the end of
November. Then, warned by the sky, cautious mountaineers, together with the
wild sheep, deer, and most of the birds and bears, make haste to the
lowlands or foothills; and burrowing marmots, mountain beavers, wood-rats,
and such people go into winter quarters, some of them not again to see the
light of day until the general awakening and resurrection of the spring in
June or July. The first heavy fall is usually from about two to four feet in
depth. Then, with intervals of splendid sunshine, storm succeeds storm,
heaping snow on snow, until thirty to fifty feet has fallen. But on account
of its settling and compacting, and the almost constant waste from melting
and evaporation, the average depth actually found at any time seldom exceeds
ten feet in the forest region, or fifteen feet along the slopes of the
summit peaks.
Even during the coldest
weather evaporation never wholly ceases, and the sunshine that abounds
between the storms is sufficiently powerful to melt the surface more or less
through all the winter months. Waste from melting also goes on to some
extent on the bottom from heat stored up in the rocks, and given off slowly
to the snow in contact with them, as is shown by the rising of the streams
on all the higher regions after the first snowfall, and their steady,
sustained flow all winter.
The greater portion of the
snow deposited around the lofty summits of the range falls in small crisp
flakes and broken crystals, or, when accompanied by strong winds and low
temperature, the crystals, instead of being locked together in their fall to
form tufted flakes, are beaten and broken into meal and fine dust. But down
in the forest region the greater portion comes gently to the ground, light
and feathery, some of the flakes in mild weather being nearly an inch in
diameter, and it is evenly distributed and kept from drifting to any great
extent by the shelter afforded by the large trees. Every tree during the
progress of gentle storms is loaded with fairy bloom at the coldest and
darkest time of year, bending the branches, and hushing every singing
needle. But as soon as the storm is over, and the sun shines, the snow at
once begins to shift and settle and fall from the branches in miniature
avalanches, and the white forest soon becomes green again. The snow on the
ground also settles and thaws every bright day, and freezes at night, until
it becomes coarsely granulated, and loses every trace of its rayed
crystalline structure, and then a man may walk firmly over its frozen
surface as if on ice. The forest region up to an elevation of seven thousand
feet is usually in great part free from snow in June, but at this time the
higher regions are still heavy-laden, and are not touched by spring weather
to any considerable extent before the middle or end of July.
One of the most striking
effects of the snow on the mountains is the burial of the rivers and small
lakes.
"As the snaw fa's in the river
A moment white, then lost forever,"
sang Burns, in illustrating
the fleeting character of human pleasure. The first snowflakes that fall
into the Sierra rivers vanish thus suddenly; but in great storms, when the
temperature is low, the abundance of the snow at length chills the water
nearly to the freezing-point, and then, of course, it ceases to melt and
consume the snow so suddenly. The falling flakes and crystals form
cloud-like masses of blue sludge, which are swept forward with the current
and carried down to warmer climates many miles distant, while some are
lodged against logs and rocks and projecting points of the banks, and last
for days, piled high above the level of the water, and show white again,
instead of being at once "lost forever," while the rivers themselves are at
length lost for months during the snowy period. The snow is first built out
from the banks in bossy, overcurling drifts, compacting and cementing until
the streams are spanned. They then flow in the dark beneath a continuous
covering across the snowy zone, which is about thirty miles wide. All the
Sierra rivers and their tributaries in these high regions are thus lost
every winter, as if another glacial period had come on. Not a drop of
running water is to be seen excepting at a few points where large falls
occur, though the rush and rumble of the heavier currents may still be
heard. Toward spring, when the weather is warm during the day and frosty at
night, repeated thawing and freezing and new layers of snow render the
bridging-masses dense and firm, so that one may safely walk across the
streams, or even lead a horse across them without danger of falling through.
In June the thinnest parts of the winter ceiling, and those most exposed to
sunshine, begin to give way, forming dark, rugged-edged, pit-like sinks, at
the bottom of which the rushing water may be seen. At the end of June only
here and there may the mountaineer find a secure snow-bridge. The most
lasting of the winter bridges, thawing from below as well as from above,
because of warm currents of air passing through the tunnels, are strikingly
arched and sculptured; and by the occasional freezing of the oozing,
dripping water of the ceiling they become brightly and picturesquely icy. In
some of the reaches, where there is a free margin, we may walk through them.
Small skylights appearing here and there, these tunnels are not very dark.
The roaring river fills all the arching way with impressively loud
reverberating music, which is sweetened at times by the ouzel, a bird that
is not afraid to go wherever a stream may go, and to sing wherever a stream
sings.
All the small alpine pools
and lakelets are in like manner obliterated from the winter landscapes,
either by being first frozen and then covered by snow, or by being filled in
by avalanches. The first avalanche of the season shot into a lake basin may
perhaps find the surface frozen. Then there is a grand crashing of breaking
ice and dashing of waves mingled with the low, deep booming of the
avalanche. Detached masses of the invading snow, mixed with fragments of
ice, drift about in sludgy, island-like heaps, while the main body of it
forms a talus with its base wholly or in part resting on the bottom of the
basin, as controlled by its depth and the size of the avalanche. The next
avalanche, of course, encroaches still farther, and so on with each in
succession until the entire basin may be filled and its water sponged up or
displaced. This huge mass of sludge, more or less mixed with sand, stones,
and perhaps timber, is frozen to a considerable depth, and much sun-heat is
required to thaw it. Some of these unfortunate lakelets are not clear of ice
and snow until near the end of summer. Others are never quite free, opening
only on the side opposite the entrance of the avalanches. Some show only a
narrow crescent of water lying between the shore and sheer bluffs of icy
compacted snow, masses of which breaking off float in front like icebergs in
a miniature Arctic Ocean, while the avalanche heaps leaning back against the
mountains look like small glaciers. The frontal cliffs are in some instances
quite picturesque, and with the berg-dotted waters in front of them lighted
with sunshine are exceedingly beautiful. It often happens that while one
side of a lake basin is hopelessly snow-buried and frozen, the other,
enjoying sunshine, is adorned with beautiful flower gardens. Some of the
smaller lakes are extinguished in an instant by a heavy avalanche either of
rocks or snow. The rolling, sliding, ponderous mass entering on one side
sweeps across the bottom and up the opposite side, displacing the water and
even scraping the basin clean, and shoving the accumulated rocks and
sediments up the farther bank and taking full possession. The dislodged
water is in part absorbed, but most of it is sent around the front of the
avalanche and down the channel of the outlet, roaring and hurrying as if
frightened and glad to escape.
SNOW-BANNERS
The most magnificent storm
phenomenon I ever saw, surpassing in showy grandeur the most imposing
effects of clouds, floods, or avalanches, was the peaks of the High Sierra,
back of Yosemite Valley, decorated with snow-banners. Many of the starry
snow-flowers, out of which these banners are made, fall before they are
ripe, while most of those that do attain perfect development as six-rayed
crystals glint and chafe against one another in their fall through the
frosty air, and are broken into fragments. This dry fragmentary snow is
still further prepared for the formation of banners by the action of the
wind. For, instead of finding rest at once, like the snow which falls into
the tranquil depths of the forests, it is rolled over and over, beaten
against rock ridges, and swirled in pits and hollows, like boulders,
pebbles, and sand in the pot-holes of a river, until finally the delicate
angles of the crystals are worn off, and the whole mass is reduced to dust.
And whenever storm-winds find this prepared snow-dust in a loose condition
on exposed slopes, where there is a free upward sweep to leeward, it is
tossed back into the sky, and borne onward from peak to peak in the form of
banners or cloudy drifts, according to the velocity of the wind and the
conformation of the slopes up or around which it is driven. While thus
flying through the air, a small portion makes good its escape, and remains
in the sky as vapor. But far the greater part, after being driven into the
sky again and again, is at length locked fast in bossy drifts, or in the
wombs of glaciers, some of it to remain silent and rigid for centuries
before it is finally melted and sent singing down the mountain-sides to the
sea.
Yet, notwithstanding the
abundance of winter snow-dust in the mountains, and the frequency of high
winds, and the length of time the dust remains loose and exposed to their
action, the occurrence of well-formed banners is, for causes we shall
hereafter note, comparatively rare. I have seen only one display of this
kind that seemed in every way perfect. This was in the winter of 1873, when
the snow-laden summits were swept by a wild "norther." I happened at the
time to be wintering in Yosemite Valley, that sublime Sierra temple where
every day one may see the grandest sights. Yet even here the wild gala day
of the north wind seemed surpassingly glorious. I was awakened in the
morning by the rocking of my cabin and the beating of pine burs on the roof.
Detached torrents and avalanches from the main wind flood overhead were
rushing wildly down the narrow side canons, and over the precipitous walls,
with loud resounding roar, rousing the pines to enthusiastic action, and
making the whole valley vibrate as though it were an instrument being
played.
But afar on the lofty exposed
peaks of the range standing so high in the sky, the storm was expressing
itself in still grander characters, which I was soon to see in all their
glory. I had long been anxious to study some points in the structure of the
ice cone that is formed every winter at the foot of the Upper Yosemite Fall,
but the blinding spray by which it is invested had hitherto prevented me
from making a sufficiently near approach. This morning the entire body of
the fall was torn into gauzy shreds, and blown horizontally along the face
of the cliff, leaving the cone dry; and while making my way to the top of an
overlooking ledge to seize so favorable an opportunity to examine the
interior of the cone, the peaks of the Merced group came in sight over the
shoulder of the South Dome, each waving a resplendent banner against the
blue sky, as regular in form, and as firm in texture, as if woven of fine
silk. So rare and splendid a phenomenon, of course, overbore all other
considerations, and I at once let the ice cone go, and began to force my way
out of the valley to some dome or ridge sufficiently lofty to command a
general view of the main summits, feeling assured that I should find them
bannered still more gloriously; nor was I in the least disappointed. Indian
Canon, through which I climbed, was choked with snow that had been shot down
in avalanches from the high cliffs on either side, rendering the ascent
difficult; but inspired by the roaring storm, the tedious wallowing brought
no fatigue, and in four hours I gained the top of a ridge above the valley,
eight thousand feet high. And there in bold relief, like a clear painting,
appeared a most imposing scene. Innumerable peaks, black and sharp, rose
grandly into the dark blue sky, their bases set in solid white, their sides
streaked and splashed with snow, like ocean rocks with foam; and from every
summit, all free and unconfused, was streaming a beautiful silky silvery
banner, from half a mile to a mile in length, slender at the point of
attachment, then widening gradually as it extended from the peak until it
was about one thousand or fifteen hundred feet in breadth, as near as I
could estimate. The cluster of peaks called the "Crown of the Sierra," at
the head of the Merced and Tuolumne Rivers, — Mounts Dana, Gibbs, Conness,
Lyell, Maclure, Ritter, with their nameless compeers, — each had its own
refulgent banner, waving with a clearly visible motion in the sunglow, and
there was not a single cloud in the sky to mar their simple grandeur. Fancy
yourself standing on this Yosemite ridge looking eastward. You notice a
strange garish glitter in the air. The gale drives wildly overhead with a
fierce, tempestuous roar, but its violence is not felt, for you are looking
through a sheltered opening in the woods as through a window. There, in the
immediate foreground of your picture, rises a majestic forest of silver fir
blooming in eternal freshness, the foliage yellow-green, and the snow
beneath the trees strewn with their beautiful plumes, plucked off by the
wind. Beyond, and extending over all the middle ground, are somber swaths of
pine, interrupted by huge swelling ridges and domes; and just beyond the
dark forest you see the monarchs of the High Sierra waving their magnificent
banners. They are twenty miles away, but you would not wish them nearer, for
every feature is distinct, and the whole glorious show is seen in its right
proportions. After this general view, mark how sharply the dark snowless
ribs and buttresses and summits of the peaks are defined, excepting the
portions veiled by the banners, and how delicately their sides are streaked
with snow, where it has come to rest in narrow flutings and gorges. Mark,
too, how grandly the banners wave as the wind is deflected against their
sides, and how trimly each is attached to the very summit of its peak, like
a streamer at a masthead; how smooth and silky they are in texture, and how
finely their fading fringes are penciled on the azure sky. See how dense and
opaque they are at the point of attachment, and how filmy and translucent
toward the end, so that the peaks back of them are seen dimly, as though you
were looking through ground glass. Yet again observe how some of the
longest, belonging to the loftiest summits, stream perfectly free all the
way across intervening notches and passes from peak to peak, while others
overlap and partly hide each other. And consider how keenly every particle
of this wondrous cloth of snow is flashing out jets of light. These are the
main features of the beautiful and terrible picture as seen from the forest
window; and it would still be surpassingly glorious were the fore- and
middle-grounds obliterated altogether, leaving only the black peaks, the
white banners, and the blue sky.
Glancing now in a general way
at the formation of snow-banners, we find that the main causes of the
wondrous beauty and perfection of those we have been contemplating were the
favorable direction and great force of the wind, the abundance of snow-dust,
and the peculiar conformation of the slopes of the peaks. It is essential
not only that the wind should move with great velocity and steadiness to
supply a sufficiently copious and continuous stream of snow-dust, but that
it should come from the north. No perfect banner is ever hung on the Sierra
peaks by a south wind. Had the gale that day blown from the south, leaving
other conditions unchanged, only a dull, confused, foglike drift would have
been produced; for the snow, instead of being spouted up over the tops of
the peaks in concentrated currents to be drawn out as streamers, would have
been shed off around the sides, and piled down into the glacier wombs. The
cause of the concentrated action of the north wind is found in the peculiar
form of the north sides of the peaks, where the amphitheaters of the
residual glaciers are. In general the south sides are convex and irregular,
while the north sides are concave in both their vertical and horizontal
sections; the wind in ascending these curves converges toward the summits,
carrying the snow in concentrating currents with it, shooting it almost
straight up into the air above the peaks, from which it is then carried away
in a horizontal direction.
This difference in form
between the north and south sides of the peaks was almost wholly produced by
the difference in the kind and quantity of the glaciation to which they have
been subjected, the north sides having been hollowed by residual shadow
glaciers of a form that never existed on the sun-beaten sides.
It appears, therefore, that
shadows in great part determine not only the forms of lofty icy mountains,
but also those of the snow-banners that the wild winds hang on them. |
