An alluvial fan . a fan-shaped mass of sediment deposited at the base of a mountain front due to an abrupt change in stream gradient is another name for a small delta forming along a beach a plant that grows in deltas and is diagnostic of a delta a fan-shaped sediment mass generated by a distributary channel

An alluvial fan is a triangle-shaped mass of sediment deposited at the base of a mountain front due to an abrupt change in stream, but they are similar to delta in shape.

Explanation:

An alluvial fan is a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment called alluvium, such as silt. Alluvial fans are the result of running water through the mountains, hills, and canyons.

Deltas are similar to alluvial fans in shape, but the environment where they are deposited is different, as sediments that form deltas are transported in continuous flowing water and deposited at the mouths of streams and rivers as they finish their way into lakes or oceans.