Where are deltas formed and why are they formed there?

Answer 1

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.

Answer 2

Deltas are formed at the mouth of rivers where sediment and debris carried by the river are deposited as the flow slows down and spreads out in a larger body of water, like an ocean or a lake. The formation of deltas is influenced by factors such as the volume of water discharged by the river, the speed of water flow, and the type of sediment being carried.