Alabama Hills - Geology

Geology

The rounded contours of the Alabamas contrast with the sharp ridges of the Sierra Nevada to the west. Though this might suggest that they formed from a different orogeny, the Alabamas are the same age as the nearby Sierras. The difference in wear can be accounted for by different patterns of erosion.

Mount Whitney, the tallest mountain in the contiguous United States, towers several thousand feet above this low range, which itself is 1,500 feet (460 m) above the floor of Owens Valley. However, gravity surveys indicate that the Owens Valley is filled with about 10,000 feet (3,000 m) of sediment and that the Alabamas are the tip of a very steep escarpment. This feature may have been created by many earthquakes similar to the 1872 Lone Pine earthquake which, in a single event, caused a vertical displacement of 15–20 feet.

There are two main types of rock exposed at Alabama Hills. One is an orange, drab weathered metamorphosed volcanic rock that is 150-200 million years old. The other type of rock exposed here is 82-85 million year old biotite monzogranite which weathers to potato-shaped large boulders, many of which stand on end due to spheroidal weathering acting on many nearly vertical joints in the rock.

Dozens of natural arches are among the main attractions at the Alabama Hills. They can be accessed by short hikes from the Whitney Portal Road, the Movie Flat Road and the Horseshoe Meadows Road. Among the notable features of the area are: Mobius Arch, Lathe Arch, the Eye of Alabama and Whitney Portal Arch.