AS Geography - Costal Enviroments

a revison set of costal enviroments

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Coasts are systems - They have inputs, processes a

Inputs - River sediment from cliffs that have been eroded or suffered landslides, and sediment that have been transported by waves from offshore (out at sea).

Processes - Wave action, tidal movements, erosion, weathering, transportation, deposition.

Outputs - Sediment washed out to sea, or deposited further along the coast.

Coastal sediment calls ( also called Littoral cells ) are lengths of coastline that are pretty much entirely self-contained for the movement of sediment. Each one is a coastal system. so processes going on in one cell don't affect the movement of sediment in another cell.

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Waves are Responsible for Erosion and Deposition o

Waves are created by the wind  blowing over the surface of the sea. The friction between the wind and the surface of the sea gives the water a circular motion.

The effect of a wave on the shore depends on its height. Wave heights affected by the wind speed and the fetch of the wave. The fetch is the maximum distance of the sea the wind has blown over in creating the waves. A high wind speed and a long fetch create high waves.

As waves approach the shore they break. Friction with the sea bed slows the bottom of the waves and makes their motion more elliptical ( squashed and oval-shape ).The crest of the wave rises up and then collapses.

Water washing up the beach is called the swash. water washing back towards the sea is called the backwash.

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Constructive and Destructive waves

Constructive waves ( waves (

Constructive waves have a low frequency ( only around 6-8 waves per minute ). They're low and long, which gives them a more elliptical cross profile. The powerful swash carries material up the beach and deposits it.

Destructive waves are high and steep, with a more circular cross profile. They have  a higher ferequency ( 10-14 wave a minuite ). the strong backwash removes material from the beach.     

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Tides Affect Where Waves Break

Tides are the periodic rise and fall of the ocean surface. They're caused by the gravitational pull of the moon and the sun. Tides affect the position at which waves break on the beach ( at high tide they break higher up the shore ). The area of land between maximum high tide and minimum low tide is where landforms are created and destroyed.                          


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Sub-aerial Weathering Occurs Along the Coastline

Sub-aerial weathering describes coastal processes that are not linked to action of the sea. It includes freeze-thaw weathering and salt weathering. weathering weakens cliffs and makes them more vulnerable to erosion.

Throughflow ( the flow of water through the cliffs ) and runoff ( the flow of water over the land ) caused by heavy rain can also make cliffs more unstable and increase the likihood of mass movement.

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