What is a delta primarily formed by?

A delta is primarily formed by the deposition of sediment. When a river flows into a larger body of water, such as an ocean or a lake, its velocity decreases significantly, causing it to lose the energy necessary to carry sediments. As a result, the river drops the sediment it has been carrying, contributing to the formation of landforms known as deltas. These deposits can accumulate over time, creating a triangular or fan-shaped area at the river's mouth, which is characteristic of deltas.

The process of sediment deposition typically involves materials like sand, silt, and clay being transported by the river and then settling as the water slows down. This continuous deposition not only shapes the delta's structure but also contributes to the rich ecosystems often found in these areas, making them fertile ground for agriculture and a habitat for diverse wildlife.