Which term refers to the sediments deposited at the mouth of a river?

The sediments deposited at the mouth of a river are known as deltas. Deltas form when a river slows down as it enters a standing body of water, such as an ocean, sea, or lake. This reduction in speed allows the river to drop the sediments it has been carrying, leading to the accumulation of material that creates landforms characterized by a triangular or fan shape. The build-up of these sediments can alter the landscape and create rich ecosystems, making deltas significant both environmentally and for human activities like agriculture and fishing.

Alluvium refers to the general term for sediments deposited by flowing water, but it doesn't specifically describe the landform created at the mouth of a river. Estuaries describe the transitional area where freshwater from rivers meets and mixes with saltwater from the sea, while floodplains are flat areas adjacent to rivers that may be flooded during high flows, but they are not specifically located at the river’s mouth. Understanding these distinctions helps clarify the unique role that deltas play in geomorphology and ecology.