Find and Fix Coastal Processes
Find and Fix > Coastal Processes
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Below are the answers to the Find questions for the Find and Fix Coastal Processes assignment. Use the information below to improve your answers if you need to. Use a different coloured pen to show your improvements. When you’ve reviewed your answers, any areas where you did not do as well as you would have liked, complete the corresponding activity on the back of your Find and Fix sheet.
The four processes of coastal transportation are traction, saltation, suspension and solution.
Waves hitting the base of a cliff cause air to be compressed in cracks, joints and folds in bedding planes, causing repeated changes in air pressure. As air rushes out of the cliff, the wave retreats, which creates an explosive effect as pressure is released. This process is supported further by the weakening effect of weathering. The material breaks off cliffs, sometimes in huge chunks. This process is known as hydraulic action.
Longshore (littoral) drift is the movement of material along the shore by wave action. It happens when waves approach the beach at an angle. The swash (waves moving up the beach) carries material up and along the beach. The backwash (waves moving back down the beach) carries material back down the beach at right angles. This is the result of gravity. This process slowly moves material along the beach.
Coastal erosion that leads to cliff collapse is facilitated through several processes, including:
- Hydraulic action – waves crashing against cliffs force air into cracks, exerting pressure and causing rocks to break away.
- Abrasion – waves carrying sand and stones scrape against the cliff face, gradually wearing it down.
- Attrition – rock particles carried by the waves collide with each other and the cliff, breaking down into smaller, rounded pieces, contributing to the material available for abrasion.
- Solution – soluble rocks such as chalk and limestone dissolve in the slightly acidic seawater, leading to cliff weakness and collapse.
Deposition is when material that is being transported is dropped by constructive waves. It happens because waves have less energy. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves. Deposition is likely to occur when waves enter an area of shallow water as wave energy reduces due to friction with the sea bed, in sheltered areas such as bays where wave energy is reduced, where a river flows into the sea, reducing its capacity to transport material and where there is a good supply of material, and the amount of material being transported is greater than the wave energy can transport.
In an exam, this question could be worth four marks.
The depositional landform in the image is a spit, a sand or shingle beach joined to the land but projects out (downdrift) into the sea. Longshore drift transports sand along the coast. The direction of the prevailing wind determines the direction of LSD. Spits form where the coastline suddenly changes shape or at the mouth of an estuary. Sand or shingle builds up in the sheltered lee side of the headland. This will continue to build up. The finer material is carried out into, the deeper water of the estuary and is deposited as the water loses its capacity to transport it further. A spit will continue to grow until the water becomes too deep or until material is removed faster than it is deposited. The end of the spit may begin to curve as wave refraction carries material into the more sheltered water. Wind and waves may also push the spit material back towards the mainland. The spit will not grow across the estuary as the river carries the material seaward.
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