Here's why:
* Alluvium: This refers to the sediment (rock, sand, silt, clay) transported and deposited by a river.
* Fan: The shape of the deposit often resembles a fan, with the widest part at the base of the mountain range and narrowing as it extends out onto the flatter land.
As a river flows down a mountain, its velocity decreases as it enters the flatter terrain. This decrease in velocity causes the river to lose energy and deposit the sediment it was carrying. Over time, this deposited material builds up, creating a fan-shaped landform.
