Seen in the bottom foreground is part of a large alluvial fan in Death Valley, California. Alluvial fans are cone-shaped piles of sediments deposited at the mouths of desert canyons. They consist principally of poorly-sorted, coarse-grained materials - gravel and sand. Deposition occurs during flash flood events. Normally-dry washes in mountainous canyons experience highly intermittent high-flow events. During such episodes, moving water has sufficient energy to transport large volumes of heavy cobbles and boulders out onto adjacent valley floors. This fan has a lithic gravel-dominated top surface.

This alluvial fan is located along Death Valley's northeastern margin. Death Valley is a graben - a down-dropped block formed by extensional tectonics. The mountain range in the distance (Cottonwood Mountains) is a horst - an uplifted block formed by the same process. In terrains with horsts and grabens, major normal faults define the boundaries between mountain ranges and valleys. Death Valley is an especially low graben. Its valley floor reaches well below sea level (about 280 feet).

Notice that, in the distance, several alluvial fans have coalesced together along the base of the Cottonwood Mountains. An extensive deposit of laterally-coalesced alluvial fans is known as a bajada.