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Faults and fissures in the Long Valley Area, California

The area surrounding Long Valley caldera and the Mono-Inyo Craters volcanic chain is cut by a complicated mix of dozens of major north-northwest trending faults and down-faulted blocks called "grabens." The eastern escarpment of the Sierra Nevada along the west margin of the caldera has developed over the past 2.5 million years by repeated offsets (earthquakes) along a fault zone. East of the Sierra Nevada, the Earth's crust has been slowly stretching and pulling apart. This extension of the crust has resulted in a series of parallel valleys (down-faulted grabens) and mountains that are bound by major faults. This is know as the Basin and Range provice, and it extends from the Sierra Nevada across Nevada to the Wasatch Range in central Utah. The many smaller faults within the caldera are related to the intrusion of magma beneath the Inyo Craters, growth of the resurgent dome, and formation of the caldera itself.