Constructive wave
Find out more about constructive waves.
Destructive waves
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Weak swash, strong backwash.
Find out more about destructive waves.
Waves are caused by the transfer of energy from the wind to the sea due to the friction of the wind on the water’s surface.
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Backwash
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Coastal erosion is the wearing away of the land by the sea.
Find out more about the processes of coastal erosion.
Corrasion, abrasion, hydraulic action, attrition and corrosion/solution.
Find out more about the processes of coastal erosion.
Abrasion occurs as breaking waves, concentrated between the high and low watermarks, which contain sand and larger fragments wear away the base of a cliff or headland. It is commonly known as the sandpaper effect. This process is particularly common in high-energy storm conditions.
Find out more about coastal erosion.
Corrosion/solution is when certain types of cliff erode as a result of weak acids in the sea.
Find out more about the processes of coastal erosion.
Waves hitting the base of a cliff causes leads to air compression in cracks, joints and folds in bedding planes, causing repeated changes in air pressure. As air rushes out of the crack when the wave retreats, it leads to 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.
Find out more about coastal erosion.
Recently weathered rock can be seen at the foot of chalk and limestone cliffs and is easily identified because it is angular.
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Mechanical weathering is the breakdown of rock without changing its chemical structure (composition).
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Chemical weathering is the breakdown of rock through changing its chemical composition.
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Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through). Water enters the rock and freezes. The ice expands by around 9%. This causes pressure on the rock until it cracks. Repeated freeze-thaw can cause the rock to break up.
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Salt weathering is when salt spray from the sea gets into a crack in a rock. It may evaporate and crystallise, putting pressure on the surrounding rock and weakening the structure.
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Wave energy reduces leading to material being deposited.
Find out more about coastal deposition.
Traction – large pebbles and boulders are rolled along the seafloor.
Find out more about coastal transportation.
Longshore drift 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 and provides a link between erosion and deposition. The material is transported through suspension, traction, solution and saltation. Longshore drift provides a link between erosion, transportation and deposition.
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Beach material is bounced along the seafloor.
Find out more about coastal transportation.
Material is dissolved and carried by the water.
Find out more about coastal transportation.
