Little Yosemite Valley - Geology

Geology

The north wall of Little Yosemite has not been subject to the same kinds of glacial planing as the south wall because the granite rocks of Moraine Dome and Sugar Bowl Dome are tougher and more resistant. This is remarkable considering that it is likely that Little Yosemite was not only scoured repeatedly by glaciers that were wholly contained by the canyon, but also overrun by glaciers that overflowed the Merced canyon and spread widely into surrounding uplands with occasional surges of ice contributed over the pass from the overflowing Tuolumne River basin. These rocks were thus subject to tremendous gravitational and flow forces yet retain a remarkable degree of integrity, eroding almost exclusively and superficially along exfoliation joints.

The south wall of the valley has been subject to extensive glacial planing, with all jointed granite completely smoothed away, leaving a stark, featureless unjointed sheer cliff face, as is apparent in the image of Little Yosemite Valley from Washburn Point, above right. The west end and south wall of the canyon are "exceptionally massive, few cliffs anywhere in the Yosemite region exhibit a more complete absence of fractures." This also leads to an almost complete absence of vegetation as well, as there are few opportunities for roothold. The north wall in contrast, and similarly to the north wall of Yosemite Valley, has been subject to much less glacial planing and is much more differentiated and vegetated.