Which process is responsible for the formation of a delta?

The formation of a delta is primarily due to the process of sediment deposition at river mouths. When a river flows toward a larger body of water, such as an ocean or a lake, its velocity decreases as it encounters the still water. This decrease in speed causes the sediment carried by the river—sand, silt, and clay—to settle and accumulate at the mouth of the river. Over time, these deposits build up, creating a landform known as a delta.

Deltas are typically characterized by their fan or triangular shape, which is a result of the sediment being distributed in various directions as the river splits into smaller channels called distributaries. This process is crucial for ecosystems, providing fertile land and habitats for a diverse range of flora and fauna due to the richness of the deposited materials.

Other processes listed—such as coral reef growth, glacier movement, and sea-level rise—do not contribute directly to delta formation and are related to different geological and ecological phenomena. Coral reefs grow in marine environments and are not connected to river sediment processes. Glacier movement influences landforms primarily through erosion and deposition but operates in different contexts than river dynamics. Sea-level rise can affect coastal areas but does not directly create deltas; rather, it could potentially submerge existing