Material carried by the sea (sand, silt, mud, pebbles) is known as its load . The load is moved up the shore by the force of the incoming waves (the swash), and back down when it is pulled by the retreating waves (backwash). This is known as longshore drift .
Backwash carries material back down the beach at a right angle
Process 1 Waves approach the shore from the side.
2 The swash pushes the material up the beach at an angle.
3 The backwash drags the material back down the beach at a right angle.
AB C Third
First position of pebble
Second position
position
Waves approach beach at an angle – often determined by the prevailing wind (the usual wind in an area/region, referring to the direction of the wind)
4 As the processes repeat, the material is moved in a zig-zag patt ern along the shore.
2. Longshore drift Deposition by the Sea
When the power of waves is reduced, the sea will drop its load because it loses energy. This can happen in: Sheltered bays Gently sloping coastal areas
Shallow water.
Question Time
1. (a) Name the two types of wave. (b) Outline the difference between the two types.
2. Explain the terms swash and backwash. 3. Name the five processes of erosion at the coast. 4. Explain how compressed air has an impact on the coastline. 5. What is the load carried by the sea made up of? 6. Using a labelled diagram, describe the process of longshore drift. 7. Where does the sea drop its load?