Big Wall Geology
The North American Wall
Look halfway up the cliff at the darker rock
shaped like a map of North America. While
El Capitan's older granite cooled below the
earth's surface, darker "North American"
diorite intruded into cracks.
The mix of different rock - seven kinds of
granite in Yosemite Valley - determines the
vertical scenery. From the colors, veins and
chemistry of cliffs, you can begin to predict
the future landscape. Sheer cliffs are the
hardest, most weather-resistant granite.
Contrast El Capitan with the Rockslides just
downvalley, a cascade of broken stone.
