Coastal Processes. Creating waves Constructive waves Destructive waves Processes of erosion Processes of transportation Longshore drift - Summary. Creating waves
Constructive waves allow material to be deposited along the coastline and form features such as spits, tombolos and bars
Destructive waves erode the coastline and help form features such as wave cut platforms, headlands, bays, arches, stacks, caves and stumps
Hydraulic action results from the weight of water hitting the coast.Air trapped in cracks is suddenly compressed by the breaking waves, which increases the pressure on the rocks. This type of erosion is greatest in storm conditions.
CORRASION (also called Abrasion ):
Breaking waves throw sand and pebbles against the cliff face which scrape away at the rock. This can cause undercutting at the base of a cliff.
ATTRITION:Particles are reduced in size as they collide with the rock face and with each other in the breaking waves. They become smaller and more rounded.
CORROSION (also called solution):
This is the dissolving action of sea water on the rocks and it is most effective on limestone rocks.
Traction: This is when rocks and heavy boulders are dragged along the sea bed. This would usually occur when the waves do not have enough energy to carry the material
Saltation: This is when smaller boulders are bounced along the sea bed
Suspension: Material such as sand grains, are carried along in the water in suspension
Solution: Lime from chalk and limestone rocks dissolves and is carried in solution
The transport of sand and pebbles along the coast is called LONGSHORE DRIFT
Waves often approach the coast at an angle and the swash carries the sand and pebbles up the beach at the same angle.The backwash, however carries the material back down the beach at right angles as this is the steepest gradient.
This causes the material to move along the coastline in a zig-zag motion and the material will eventually be deposited when the waves lose energy.
The general direction of longshore drift is decided by the prevailing wind direction.