Deposition Flashcards
In what two ways can deposition occur?
Gravity settling
Flocculation
What is gravity settling?
This occurs when the energy of transporting water becomes too low to move sediment.
Large sediment will be deposited first followed by smaller sediment (pebbles-sand-silt)
What is flocculation?
Depositional process that is important for very small particles, such as clay, which are so small that they will remain suspended in water.
Clay particles clump together through electrical or chemical attraction, and become large enough to sink.
How is a spit formed?
It is a sand or a shingle beach ridge extending beyond a turn in the coastline, usually greater than 30 degrees.
At the turn, the longshore drift current spreads out and loses energy, leading to deposition.
The length of a spit is determined by the existence of secondary currents causing erosion, either the flow of a river or wave action which limits its length
How is a bayhead beach formed?
Waves break at 90 degrees to the shoreline and move sediment into a bay, where a beach forms.
Through wave refraction, erosion is concentrated at headlands and the bay is an area of deposition.
How is a tombolo formed?
It is a sand or shingle bar that links the coast to an offshore island.
Form as a result of wave refraction around an offshore island which creates an area of calm water and deposition between island and coast.
How is a barrier beach/bar formed?
Sand or shingle beach connecting two areas of land, with a shallow water lagoon behind it.
Forms when a spit grows so long that it extends across a bay, closing it off.
How is a hooked/recurved spit formed?
It is a spit whose end is curved landward. The seaward end of the spit naturally curves landward into shallower water and the ‘hook’ may be made more pronounced by waves from a secondary direction of the prevailing wind.
How is a cuspate foreland formed?
It is a roughly triangular shaped feature extending out from a shoreline.
There is debate about its formation.
One hypothesis suggests that it results from the growth of two spits from opposing longshore drift directions.
How does vegetation play an important role?
It stabalises depositional landforms.
Plant succession in the form of slat marshes and sand dunes, bind the loose sediment together and encourages further deposition.
