The geographical feature formed by the deposition of sediment at the mouth of a river is known as a delta. Deltas are created as rivers slow down upon entering a larger body of water, depositing sediments that accumulate over time. This process creates fertile land that is often ideal for agriculture. Deltas can be rich ecosystems, supporting a wide variety of wildlife and vegetation. Famous examples include the Mississippi Delta in the United States and the Ganges-Brahmaputra Delta in India and Bangladesh, which are vital to their respective regions' economies and cultures.