silt
Sedimentation
It drops the material. This is called deposition :)
It is called a delta
Deltain Peru
Sediment and small rocks are carried down in the river and are deposited.
A deposit that forms where a river leaves a mountain range is called an alluvial fan. This fan-shaped deposit is created as the river slows down and deposits sediment and debris that it has carried from the mountains.
Material will travel faster in a river flowing down a steep slope. As the water slows down, the material will also slow down.
Alluvial material is sediment that is deposited by flowing water, such as rivers or streams. It is composed of particles like sand, silt, and gravel that are carried by the water and then deposited when the water slows down. Alluvial material is often found in floodplains and river deltas.
Well heavy earth material like sand slows down at the mouth on the river. It slows down at the mouth because at the source of the river is the fastest but as it is moving down the plain it is slowing down because of friction. Also because the eroded sand that is in the water is making the water heavier which means it will slow it down
Evolution
Erosion wears down material. Examples that you can see in nature include mountains, river beds, and canyons.
The fan-like formation of a river is called a "delta." Deltas form at the mouth of a river where it meets a body of water, such as an ocean or lake, and sediment carried by the river is deposited as the flow slows down. This creates a triangular or fan-shaped landform, often rich in biodiversity and fertile soil.