How do deltas form?
A delta is formed when pieces of rock and sediment flow down a river and to the ocean. Over time the sediment at the mouth builds up so much that the water has to find a way around the buildup and a new place to go into the ocean. This happens for a while until a river delta forms. It is similar, in principle, to the formation of alluvial fans at the bottom of mountain canyons.
Deltas form from erosion of rocks.The river must carry enough sediment to layer into deltas over time. The river's velocity decreases rapidly, causing it to deposit the majority.An alluvium builds up to form the river delta. A river delta is a landform that forms at the mouth of a river, where the river flows into an ocean, sea, estuary, lake, or reservoir. Deltas form from deposition of sediment carried by a river as the flow…
Where a river which transmits a great deal of material arrives at the sea and there is little tidal range a delta will form. Example the Nile into the Mediterranean or the Mississippi into the Gulf of Mexico. The Amazon & the Congo, which flow into an Ocean, the Atlantic in these examples, do not form deltas because the ocean currents distribute the outflow of material into & along the ocean currents.