costal processes Flashcards
types of coastal zones
cliffs beaches sand dunes salt marshes ports/harbours seaside resorts
Erosion
waves can erode the coastline in a similar way to the water in rivers. This usually occurs when the sea takes lots of energy from the power of destructive waves
Transportation
the movement of eroded material up and down, and along the coast.
Deposition
when the sea loses energy, it drops the sand, rock particles and pebbles that it has been carrying, depositing them.
Rock type
chalks and limestone can form steep cliffs, whereas clays and softer rock form large bays
Rock structure
a discordant coastline, where rocks are at an angle to the edge of the coastline, will erode at different rates.
The shape of the coastline
headlands of a coastline are exposed to the full force of destructive waves. Bays are more sheltered from the wave energy because of wave refraction, so erosion is slower.
The type of wave
the amount of energy a wave has helps determine the rate of erosion.
Deposition is likely to occur when:
waves enter an area of shallow water
waves enter a sheltered bay
there are calm conditions with little wind
The importance of waves
The power of waves is one of the most important forces that changes the shape of the coast. Waves are created by wind blowing over the surface of the sea.
The size of a wave depends on:
length of time the wind has been blowing
strength of the wind
‘fetch’ - how far the wind has travelled
Wave types
Waves can be constructive or destructive.
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When a wave breaks, water is washed up the beach. This is called the swash. Then the water runs back down the beach, which is called the backwash. With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger than the swash.
If the swash is stronger than the backwash (constructive wave), some of the sediment carried in the wave will be left behind to build up the beach. This means that the beach increases in size.
If the swash is weaker than the backwash (destructive wave), very little sediment is carried up the beach. With a strong backwash, material will be removed and the beach will decrease in size.
The movement of water down the beach.
backwash
bay
A low-lying inlet of land on the coast
Waves which help build up material on the beach. They tend to have a low frequency and strong swash.
constructive wave
Waves which remove material from the beach. The swash is weaker than the backwash.
destructive wave
steep cliff
Steep exposed rock face.
swash
The water flowing towards a beach when a wave breaks.
The process where a wave changes direction as it approaches the shore
wave refraction
When is deposition likely to occur?
Deposition is likely to occur when there are calm conditions with little wind. Wave energy is low here. Wave energy is high at headlands due to wave refraction.
