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Deltas
A delta is a place where material carried by a river is laid down in the sea.
The coast gets much of its sand, silt and mud by wearing away cliffs. But lots of sand, silt and mud are also brought to the sea by rivers.
When a river brings more material than the sea can wash away, the material starts to build up and forms a delta.
Fan-shaped deltas
There are two common shapes of delta. One shape is like a fan (picture ). It has many channels that spread out evenly from the main river. As a result, the sand and silt are laid down evenly around the edge of the delta and it has a smooth shape (picture 2).
Bird’s foot deltas
The other kind of delta is produced when a river has only a small number of channels
(picture 3). It resembles the shape of the claws on a bird’s foot and as a result is called a bird’s foot delta. The Mississippi Delta (picture 4) is an example of a bird’s foot delta.
Deltas make new land
As new material is laid down by rivers entering the sea, so deltas grow out from the coast and make new land.
F 3 Bird’s-foot delta. This kind of delta forms when a single main channel changes direction frequently.
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G  Fan-shaped delta. This kind of delta forms wherever channels spread out evenly across the delta.
E 2 This is the fan delta of the Irrawaddy Delta in Burma. Notice the mainly small channels spread out evenly across it. The pale blue colour in the sea is moving sand that has built up close to the surface. In time it will make new land and cause the delta to reach further into the sea.