Delta formation occurs when a river meets a body of water, such as an ocean or lake, causing the flow of water to slow down. As the river slows, it deposits sediment—small particles of soil and rock—along its mouth. Over time, these deposits build up, creating a landform known as a delta. Deltas are typically triangular or fan-shaped and can be rich in biodiversity. They provide important habitats for various species and are often fertile areas for agriculture. Famous examples of deltas include the Mississippi River Delta and the Nile Delta.