CHAPTER VIII. THE GLACIAL HISTORY OF LAKE TAHOE
We have already seen in the preceding chapter how the great basin, in which Lake Tahoe rests, was turned out in the rough from Nature's workshop. It must now be smoothed down, its angularities removed, its sharpest features eliminated, and soft and fertile banks prepared upon which trees, shrubs, plants and flowers might spring forth to give beauty to an otherwise naked and barren scene.
It is almost impossible for one to picture the Tahoe basin at this time. There may have been water in it, or there may not. All the great mountain peaks, most of them, perhaps, much higher by several thousands of feet than at present, were rude, rough, jagged masses, fresh from the factory of God. There was not a tree, not a shrub, not a flower, not a blade of grass. No bird sang its cheering song, or delighted the eye with its gorgeous plumage; not even a frog croaked, a cicada rattled, or a serpent hissed. All was barren desolation, fearful silence and ghastly newness.
What were the forces that produced so marvelous a change?
Snowflakes, - "flowers of the air", - as John Muir so poetically calls them. They accomplished the work. Falling alone they could have done nothing, but coming down in vast numbers, day after day, they piled up and became a power. Snow forms glaciers, and glaciers are mighty forces that create things.
Let us, if possible, stand and watch the Master Workman doing the work that is to make this region our source of present day joy. We will make the ascent and stand on the summit of Pyramid Peak. This is now 10,020 feet above sea level, rising almost sheer above Desolation Valley immediately at our feet.
The first thing that arrests the visitor's attention is the peculiar shape of the peak upon which he stands, and of the whole of the Crystal Range. Both east and west it is a great precipice, with a razor-like edge, which seems to have been especially designed for the purpose of arresting the clouds and snow blown over the mountain, ranges of the High Sierras, and preventing their contents falling upon the waste and thirsty, almost desert-areas of western Nevada, which lie a few miles further east.
Whence do the rains and snow-storms come?
One hundred and fifty miles, a trifle more or less, to the westward is the vast bosom of the Pacific Ocean. Its warm current is constantly kissed by the fervid sun and its water allured, in the shape of mist and fog, to ascend into the heavens above. Here it is gently wafted by the steady ocean breezes over the land to the east. In the summer the wind currents now and again swing the clouds thus formed northward, and Oregon and Washington receive rain from the operation of the sun upon the Pacific Ocean of the south. In June and July, however, the Tahoe region sees occasional rains which clear the atmosphere, freshen the flowers and trees, and give an added charm to everything. But in the fall and winter the winds send the clouds more directly eastward, and in crossing the Sierran summits the mist and fog become colder and colder, until, when the clouds are arrested by the stern barriers of the Crystal Range, and necessity compels them to discharge their burden, they scatter snow so profusely that one who sees this region only in the summer has no conception of its winter appearance. The snow does not fall as in ordinary storms, but, in these altitudes, the very heavens seem to press down, ladened with snow, and it falls in sheets to a depth of five, ten, twenty, thirty and even more feet, on the level.
Look now, however, at the western edge of the Crystal Range. It has no "slopes." It is composed of a series of absolute precipices, on the edge of one of which we stand. These precipices, and the razor edge, are fortified and buttressed by arms which reach out westward and form rude crescents, called by the French geologists cirques, for here the snow lodges, and is packed to great density and solidity with all the force, fervor and fury of the mountain winds.
But the snow does not fall alone on the western cirques. It discharges with such prodigality, and the wind demands its release with such precipitancy, that it lodges in equally vast masses on the eastern slopes of the Crystal Range. For, while the eastern side of this range is steep enough to be termed in general parlance "precipitous," it has a decided slope when compared with the sheer drop of the western side. Here the configuration and arrangement of the rock-masses also have created a number of cirques, where remnants of the winter's snow masses are yet to be seen. These snow masses are baby glaciers, or snow being slowly manufactured into glaciers, or, as some authorities think, the remnants of the vast glaciers that once covered this whole region with their heavy and slowly-moving icy cap.
On the Tallac Range the snow fell heavily toward Desolation Valley, but also on the steep and precipitous slopes that faced the north. So also with the Angora Range. Its western exposure, however, is of a fairly gentle slope, so that the snow was blown over to the eastern side, where there are several precipitous cirques of stupendous size for the preservation of the accumulated and accumulating snow.
Now let us, in imagination, ascend in a balloon over this region and hover there, seeking to reconstruct, by mental images, the appearance it must have assumed and the action that took place in the ages long ago.