What is the name given to the fan-shaped area formed at the mouth of a river?

The term used to describe the fan-shaped area formed at the mouth of a river is "delta." This occurs when sediment carried by the river is deposited as the river flows into a standing body of water, such as an ocean, sea, or lake. As the river slows down upon entering these larger bodies, it loses energy and drops its sediment load, which builds up over time to create a landform that often branches out in a triangular shape. This process can result in rich, fertile land that supports diverse ecosystems and is often vital for local agriculture.

The other terms do have specific meanings in geography. An estuary refers to the area where freshwater from rivers meets and mixes with saltwater from the ocean, benefiting from the nutrient-rich sediment that rivers contribute. A basin is a broader term describing an area of land drained by a single river system, whereas a wetland denotes a specific ecological area where water covers the soil or is present near the surface, supporting various plants and wildlife. Understanding these distinctions is essential in geography and environmental science.