Coastal Landscapes Introduction

The sea, just like rivers and ice is a very powerful agent of erosion. It erodes a variety of landforms, and just like all agents of erosion, it also transports the material it erodes and makes new landforms where it deposits this material.

Processes of coastal erosion Waves that have a lot of energy are able to erode the land at the coast. Waves erode the land by three main processes. Hydraulic action, Corrasion and solution.

Hydraulic Action This is the sheer power of the waves smashing against the cliffs, compressing the air in its cracks, which makes the cracks wider and longer until pieces of rock break off.

Corrasion This is when the sand, shingle and pebbles that waves are carrying are hurled against the cliff, causing pieces of rock to eventually break off. The rocks that break off the cliff and lie on the beach are then picked up by other waves and used to corrade the cliff even more. The rocks themselves are broken up into smaller and more rounded pieces.

Solution This occurs as salt and other chemicals in the sea water slowly dissolve minerals in the rocks, causing them to break up.

Processes of Coastal deposition The coastline of the British isles is being worn away, but this does not mean that our land will eventually disappear. The material that waves erode is deposited and builds up land elsewhere.

Waves deposit in areas where they have very little energy. They deposit the largest particles first, so the material is sorted according to size.

Processes of coastal transportation When a wave breaks near the shore and washes up the beach this is called swash. When it runs back down the beach and back into the sea, it is called backwash. Along many of our coastlines the swash travels up our beaches at an angle.

As it has some energy it picks up sand and shingle and takes them up the beach. Backwash returns to sea down the steepest slope. The backwash carries the sand and shingle with it.

The swash from the next wave then picks the same particles up and repeats the process. In this zig-zag way sand and shingle are transported along the beach. The process is called longshore drift and it takes place in the direction of the prevailing winds.

Longshore Drift

Questions 1) Describe the 3 processes by which waves erode. 2) Waves deposit ‘sorted’ particles. What does this mean? 3) What is the difference between swash and backwash? 4) What name is given to the movement of sand along a beach? 5) Using a diagram, explain how material is moved along a beach.