Fault block

Fault blocks are huge pieces of rock, sometimes stretching for hundreds of kilometers, formed by forces within the Earth's crust. These blocks are created when large areas of bedrock split apart due to faults, which are fractures in the Earth's surface. The rocks within these blocks usually have a similar type or structure, known as lithology.

The movement of these fault blocks is mostly horizontal, meaning it happens parallel to the Earth's surface, and is linked to the shifting of tectonic plates. However, when blocks move up or down, they can create striking landforms such as mountains, hills, ridges, lakes, and valleys. When one block moves up while the adjacent block drops down, it forms high cliffs called escarpments. The movement of these blocks can also cause tilting, as the crust compacts or stretches at certain points.

Fault-block mountains

See also: List of mountain types and Mountain building

Fault-block mountains form when the Earth's crust stretches apart, a process called rifting. This stretching creates long valleys and tall mountains. Examples include the East African Rift and Death Valley in California.

There are two main kinds of these mountains. One type has uplifted blocks of land between two cracks, or faults, in the Earth's surface. The other type has tilted blocks, where one side of a fault tilts upward more than the other. These tilted mountains are common in the western United States.