I can just send a picture it’s way to confusing
Answer: erosion
Explanation: Have a nice day! :3
When a river reaches a lake or the sea the water slows down and loses the power to carry sediment . The sediment is dropped at the mouth of the river. Some rivers drop so much sediment that waves and tides can't carry it all away. It builds up in layers forming a delta.
so Ur answer is Deltas are build up by deposition
