YOSEMITE
North Dome, Basket Dome and Mt. Hoffmann

The elegant convex curves of North Dome and Basket Dome contrast sharply with the eroded, irregular, snow-covered flanks of Mt. Hoffmann. More...

The elegant convex curves of North Dome and Basket Dome contrast sharply with the eroded, irregular, snow-covered flanks of Mt. Hoffmann.

North Dome and Basket Dome are prime examples of granite exfoliation domes. The aesthetic domes of Yosemite National Park are among the most viewed, trodden, photographed and studied in the world, yet their formation is not completely understood. One of the accepted mechanisms is pressure release jointing within the dome. This results in erosive exfoliation, where onion-like layers of granite are removed from the dome through the actions of water, ice, wind and gravity. Other, perhaps plutnic mechanisms that may affect the origin and eventual shape of a dome are less understood.

Geologists recognize that the expansive granites of Yosemite are not all the same. There are various intrusive granitic bodies, called plutons, each with similar characteristics, that have been emplaced at different times. For example, North Dome and Basket Dome are comprised of Half Dome Granodiorite, emplaced about 86-88 million years ago; while Mt. Hoffmann is El Capitan Granite, emplaced approximately 120 million years ago.