Mount Whitney - Geology

Geology

The eastern slope of Whitney is far steeper than its western slope. This is because the entire Sierra Nevada is the result of a fault-block that is analogous to a door: the door is hinged on the west and is slowly rising on the east. The rise is caused by a normal fault system that runs along the eastern base of the Sierra, below Mount Whitney. Thus, the granite that forms Mount Whitney is the same as the granite that forms the Alabama Hills thousands of feet below. The raising of Whitney (and the downdrop of the Owens Valley) is due to the same geological forces that cause the Basin and Range Province: the crust of much of the intermontane west is slowly being stretched.

The granite that forms Mount Whitney is part of the Sierra Nevada batholith. In Cretaceous time, masses of molten rock that originated from subduction rose underneath what is now Whitney and solidified underground to form large expanses of granite. In the last 2 to 10 million years, the Sierra was pushed up which enabled glacial and river erosion to strip the upper layers of rock to reveal the resistant granite that makes up Mount Whitney today.