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The Yosemite Valley (1910) by Galen Clark

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DURING a residence of many years in Yosemite, and a careful observation of the structural formation of the great walls on each side and the great domes in connection therewith, it seems evident to me that there were two great forces which operated at different periods of time in the origin and formation of Yosemite Valley.

In some period of the earth’s existence, while its granite crust in that locality was in a semi-plastic condition, by some great subterranean force of gases or superheated steam, its surface was forced up in places, forming these great dome elevations. In some instances this force was sufficient to burst open the surface and make a complete blow-out, forming a great chasm with vertical sides. The bursting open of two or more, of these great domes seems to have been the original agency in the formation of Yosemite Valley. I can imagine no other theory to account for the various lines of cleavage and fractures in the great walls of the Valley, some of them being vertical some horizontal, and others in various degrees of inclination and curves.

In later years, during the glacial epoch, a portion of the great glaciers which covered this part of the mountain range completed the work by crushing the remaining rock material, filling up to a great extent the deep chasms and carrying out the surplus material, and at the end of the great ice age the Valley was left a great lake which in the course of time was filled up by disintegrated granite brought in by the flood waters from the higher mountains adjacent, leaving the main picturesque features of the Valley much as we see them now.

Sentinel Dome, showing concentric rock formation, by George Fiske
Showing concentric rock formation
Ever since then Nature has been industriously at work growing trees, flowering shrubs and plants to adorn and hide from view, as much as possible, the awful desolation left by the melting glaciers; and by long exposure to the action of the elements for unknown thousands of years, to the expansion and contraction of countless summers and winters, large portions of the surface of the walls, which bore evidence of glacial erosion, have fallen away, and form the great piles of rock at the base of the cliffs on each side of the Valley.

One of Prof. Whitney’s great objections to the glacial theory of the origin of Yosemite Valley was the lack of evidence of what became of the great amount of crushed rock material which must have been created in its formation. It is evident that most of this material must have been carried away in the form of glacial mud by the great stream flowing from under the glacier down through the Merced Canyon to the San Joaquin Valley, which undoubtedly at that time was a great inland sea, and, when reaching the slack water of the sea, settled in a deposit which in the course of unknown years has been hardened into rock, forming elevated ridges near the Merced River, and much of what is called "hard pan" beneath the surface soil. in the near vicinity.

All the great and smaller canyons of the rivers which head in the High Sierras, together with the whole western face of the Sierra Nevada range of mountains, have been forced by glacial action to contribute largely in the formation of the great plains of the Sacramento and San Joaquin Valleys. The dying glaciers have therefore bequeathed to California a vast empire of agricultural wealth as well as a crowning mountain diadem of unspeakable sublimity and grandeur.

Three Brothers, by George Fiske
3,530 feet
[Photo by George Fiske]

Next: Peaks and DomesContentsPrevious: Theories Regarding Origin

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Online Library: Title Author California Geology History Indians Muir Mountaineering Nature Management