Alluvial fan

A fan-shaped depositional landform consisting of alluvial deposits that formed where a flowing stream slows and spreads out (depositing its load), typically at the base of a mountain range where there is a marked change in slope. Fan deposits tend to be coarse-grained at their mouths, but grade to finer-grained material toward their edges.

A large fan-shaped accumulation of sediment deposited by streams where they emerge at the front of a mountain range.