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Deltas:

Key words:

 

  • Flocculation

  • Topset beds

  • Foreset beds

  • Bottomset beds

  • Arcuate, Cuspate and Bird's foot deltas.

Formation:

 

  1. When a river reaches the sea, the energy of the river is absorbed by the slow moving water of the sea. 

  2. This causes deposition to occur, as velocity and carrying capacity reduces. 

  3. Flocculation occurs as fresh water mixes with seawater and clay particles coagulate due to a chemical reaction. The material becomes heavy and is deposited. Clay settles on the river bed. 

  4. These deposits of sediment build up on the sea bed, until the alluvium (deposited sediment) rises above sea level. This deposited material partially block the mouth of the river. 

  5. The river then has to braid into several tributaries in order to reach the sea forming a delta. 

Types of deposit:

 

  • The large and heavy particles are deposited first, as the river loses energy. These form the topset beds.

  • Medium graded particles travel further before they are deposited as steep angled wedges of sediment, forming the foreset beds.

  • The finest particles travel furthest and form the bottomset beds.

 

 

Types of deltas:

 

  • Cuspate 

  • Arcuate

  • Bird's foot 

 

 

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