Geologic Trip, Yosemite Valley
The Tunnel View parking area on State Route 41 directly east of the Wawona Tunnel provides a excellent view of Yosemite Valley. During the Pleistocene glacial episodes, glaciers that began in the Tuolumne icefields filled Yosemite Valley and flowed down the valley as far west as El Portal. As the glaciers moved down the valley, they broadened the floor of the valley, steepened the valley walls, and cut off the lower sections of many of the creeks that had once flowed directly into the Merced River.
When the ice melted, the upper sections of these creeks were left hanging high on the sides of the valley. Bridalveil Fall, at the right side of the photograph, is a classic example of one of these “hanging” valleys. The valley of Bridalveil Creek lies 850 feet above the floor of Yosemite Valley and the fall leaps over a 650-foot near-vertical cliff where the creek enters the valley. The creek above the waterfall slopes very steeply so that the water is propelled over the edge of the cliff with great force.