The Lore and the Lure of the Yosemite: Chapter X. Geology of the Yosemite Valley: Chapter X. Geology of the Yosemite Valley

IT is known that since the beginning of time the surface of the earth has undergone various changes brought about by its cooling and shrinking and by internal eruptions and disturbances.

During one of these disturbances the region between the Pacific Ocean and the Rocky Mountains was affected. Here the surface of the earth was broken into great blocks and one of these, four hundred miles long and eighty miles wide, was pushed up at its eastern edge, separating it from the depressed region to the east, leaving a steep scarp, and pulled down at its western edge giving it a gentle slope to the sea.

The streams which flowed in diverse directions before the uplift of this block now were given a definite course flowing down the slope to the west and forming broad shallow valleys. One of these streams was the Merced River which now flows through the Yosemite Valley.

After a great period of time there occurred a second upward thrust which raised the eastern edge of the block to an elevation of several thousand feet making a distinct mountain range, later known as the Sierra Nevada. This second uplift gave to the western side a greater incline so that the Merced River was given enough velocity to enable it, through the millions of years elapsing before a third series of uplifts, to cut a narrower valley within its old broad valley.

The tributary streams which flowed parallel to the range and at right angles to the Merced River were not benefited by the tilting of the block, hence the deeper the main river cut the higher the side streams were left above it. With the broadening and leveling of its bed the Merced lost its cutting power and flowed lazily over the valley floor.

The third and last uplift, greater than any preceding it, which raised the crest of the range to an elevation of over seven thousand feet in the north and about fourteen thousand feet in the southern part, gave to the Merced River such rapidity and power that it cut in its old valley a deep narrow canyon. The deepening of the river bed again left all of the side streams high in their hanging valleys to cascade down steep V-shaped walls to join the master stream; except Tenaya Creek with its southwesterly course, and Bridal Veil

Thus has God fashioned a Cathedral with the granite cliffs for the walls, the canopy of the heavens for the roof, and as the artist adds the last subtle touch to his masterpiece so has the Creator caused the forces of nature to deposit seeds of trees and beautiful plants to adorn the mighty cliffs and the valley floor.