As it Reaches the Sea

Most rivers end their journey when they flow into a sea. The river slows down and deposits then sediment it is carrying. Heavy grains of sand and gravel drop to the bottom while lighter particles of fine silt and clay are carried further out to sea. Eventually, the sediment spreads out to form a new piece of land with gently sloping sides. This is called a delta.

Shapes of delta.

The shape of a delta depends on how much water and sediment is carried by the river, and how fast the water is flowing. The speed and strength of the sea's waves, currents and tides are also taken into consideration.

When a lot of sediment is carried out into calm seawater, a bird's-foot delta is formed. The distributaries carry long 'toes' of sediment out into the sea. One example of such a delta is the Mississippi Delta(on left).

An arcuate delta is formed when a river meets the sea in a place where the waves, currents and tides are strong. The deltas of the Nile(on left) , Indus and Rhone are shaped like this

A cuspate delta is formed when a river drops sediment onto a straight shoreline with strong waves. Waves force the sediment to spread outwards in both directions from the river's mouth, making a pointed a tooth shaped with curved sides.