Yosemite National Park, California. The Rockslides and El Capitan. The Rockslides (left) is a jumbled collection of talus blocks of diorite, the most closely jointed rock in Yosemite Valley.

Yosemite National Park, California. The Rockslides and El Capitan. The Rockslides (left) is a jumbled collection of talus blocks of diorite, the most closely jointed rock in Yosemite Valley. In contrast, El Capitan (right) is largely unjointed granite, and the pile of debris at its foot, though concealed in this photograph, is comparatively small. Figure 37, U.S. Geological Survey Bulletin 1595.