Coastal environments

Topic 2

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  • Created by: Hannah
  • Created on: 13-01-12 11:20

Coasts are systems- They have inputs, processes an

1) INPUTS- river sediment, sediment from cliffs that have been eroded or suffered landslides, and sediment that has been transported by waves from offshore.

2) PROCESSES- wave action, tidal movement, erosion, weathering, transportation, deposition.

3) OUTPUTS- sediment washed out to sea, or deposited further along the coast.

Coastal sediment cells (littoral cells) are lengths of coastline that are pretty much are 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

1) 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.

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

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

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

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There are 2 types of wave

There are 2 types of wave:

1) Constructive waves have a low frequency (only around 6-8 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.

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

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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