Geologic Trip, Yosemite Valley
The huge granite monolith of El Capitan is the tallest unbroken cliff in the world, measuring 3,593 feet from base to summit. Although El Capitan stood directly in the path of the many Pleistocene glaciers that carved out Yosemite Valley, the monolith consists of unusually hard granite and withstood the repeated onslaught of these powerful glaciers. Most of El Capitan consists of the El Capitan Granite, one of the oldest granites in Yosemite Valley.
The grains in the granite are large, and the granite has a high percentage of quartz. Granites of this type tend to be resistant to fracturing and jointing, and it is these characteristics that enabled El Capitan to withstand the quarrying action of the glaciers that flowed down Yosemite Valley.