(a) List any two types of delta (b) Explain four conditions favorable for the formation of delta (c) Describe three main characteristics of a delta

Answer Details

(a) Two types of delta

• Arcuate (fan-shaped) delta - for example the Nile delta.
• Bird foot (finger-shaped) delta - for example the Mississippi delta.

Other acceptable types: estuarine delta and cuspate (pointed) delta.

(b) Four conditions favourable for the formation of a delta

1. Large load of sediment: the river must carry a heavy load of sand, silt and mud to deposit at its mouth.
2. Gentle gradient and reduced velocity: near the mouth the land is nearly flat, so the river slows down and drops its load.
3. Sheltered, calm sea or lake with weak tides, waves and currents, so the deposited material is not swept away.
4. Shallow water at the river mouth that fills up quickly, and a coastline that is not sinking, allowing sediment to build up above water.

Also acceptable: absence of a strong offshore current and a fairly tideless sea.

(c) Three main characteristics of a delta

• It is a low, flat, triangular or fan-shaped tract of new land built of alluvium at the mouth of a river.
• The river splits into many branches called distributaries that cross the delta to the sea.
• It is made of fertile, fine deposits (silt and mud), is often swampy or marshy, and is enclosed by lagoons and sand bars.