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Shaping Coastlines

Geography: Edexcel A Level, topic 3.2.1

Waves

Constructive and destructive waves are the two main types of wave. The characteristics of these waves are described below.

Destructive waves

Destructive waves

  • Responsible for erosional processes.
  • Happen at a high frequency (10-15 waves per minute).
  • Steep and high, with a circular motion so waves break at a greater height.
  • This causes the wave to ‘plunge’ and travel a shorter distance along the beach.
  • Destructive waves remove material from coasts because the swash is less powerful than the backwash.
Constructive waves

Constructive waves

  • Happen at a low frequency (6-9 waves per minute).
  • Long and low.
  • Over time, constructive waves will form gently sloping beaches.
  • Constructive waves deposit material on coasts because the backwash is less powerful than the swash.
  • They move in an elliptical motion, with waves breaking with little height.
  • This results in them ‘spilling’ and breaking out further along the beach.

Processes of Erosion

Erosion is the wearing away of rock. Several erosion processes happen at coastlines, with their ability to alter the shape of coasts influenced by the wave type, the coastline shape and its lithology.

Hydraulic power

Hydraulic power

  • Hydraulic power causes the breakdown of cliffs due to the force of the water being compressed into the cracks of the rock.
  • The repeated action of the water forced in and out of the cracks in the rock leads to the breakdown of the surrounding cliff.
Abrasion

Abrasion

  • Abrasion is where pieces of rock are picked up by waves and hit against the bed, the beach or cliffs. This wears them away over time.
Attrition

Attrition

  • Attrition is where pieces of bedload (material carried in the water) are hit against one another. This causes them to break apart and become smaller and more rounded.
Corrosion

Corrosion

  • Corrosion happens when there is a chemical reaction between the seawater (which contains a weak acid) and susceptible rocks like limestone.

Test yourself on Shaping Coastlines

  • What are the main types of waves?

  • Which of the following is NOT a category of wave?

  • What are the processes of erosion that affect coastal landscapes?

  • Which process of erosion involves pieces of bedload hitting into one another?

  • Which process of erosion is being shown here?

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