A river delta is a landform that occurs at the mouth of a river, where the river meets a larger body of water, such as an ocean or a lake. As the river flows, it carries sediment—small particles of soil and rock. When the river slows down upon entering the larger water body, it drops this sediment, gradually building up land over time. Deltas are often characterized by their triangular or fan-shaped appearance and can support diverse ecosystems. They provide important habitats for wildlife and are crucial for human activities, such as agriculture and fishing, due to their fertile soil and abundant resources.