A delta is a landform that occurs at the mouth of a river, where it meets a larger body of water, such as an ocean or a lake. Deltas are formed by the deposition of sediment carried by the river as the flow slows down upon entering the standing water. This process creates a triangular or fan-shaped area of land, often rich in nutrients and biodiversity. Deltas are important ecosystems that support various wildlife and plant species. They also provide fertile land for agriculture and serve as natural buffers against flooding. Famous examples of deltas include the Nile Delta in Egypt and the Mississippi River Delta in the United States.