How do deltas build up where a river meets the sea?
Quick Answer
When river water slows down, it drops sediment at its mouth. Over time, that deposited material pushes the shoreline outward and forms a delta.
The Full Story
A delta forms when a river enters a lake or ocean and loses energy. As the water slows, it can no longer carry as much sand, silt, and clay, so the sediment settles out. If deposition outpaces erosion and wave removal, the sediment pile grows outward into the body of water. Channels often split and rejoin across the surface, creating classic branching patterns. Famous deltas include the Nile, Mississippi, and Ganges-Brahmaputra, each shaped by different balances of river flow, tides, and waves.
Key Facts
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