Delta formation Flashcards
What is a delta?
A delta is a landform of deposition.
What happens as the gradient declines at the river mouth?
As the gradient declines at the mouth of the river, velocity is reduced and this reduces river discharge and energy.
What else happens as the gradient declines?
The competence and capacity of the river are slowed and the finest particles of silt and clay are deposited out at sea.
What process occurs?
The process of flocculation takes place when clay particles coagulate and settle to form a platform of gently dipping layers of sediment.
Discuss fine particles
The finest particles such as clays are transported furthest from the mouth because they are the smallest and deposited in layers to create the bottom-set beds.
Discuss medium grains
Medium grained particles are laid down at an angle as the sea deepens in foreset beds.
Discuss the coarsest material
Lastly, the coarsest materials such as gravels are deposited closest to the mouth in the top-set beds.
River processes
the river current that brings the sediment load
Sea processes
the wave and tidal action along the shoreline.
Discuss river process dominance
Where river processes dominates a bird foot delta is formed e.g. the Mississippi delta.
Discuss sea process dominance
When sea processes dominate, wave currents redistribute the river sediment along the coast in a fan shape to create an arcuate delta e.g. the Nile delta.”
