A wave is a disturbance on the surface of the sea or ocean, in the form of a moving ridge or swell.
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The distance a wave has travelled.
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Constructive and destructive waves.
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Constructive wave
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Backwash
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Corrasion, abrasion, hydraulic action, attrition and corrosion/solution.
Find out more about the processes of coastal erosion.
The wearing away of land by the sea.
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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.
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Attrition is when waves cause rocks and pebbles to bump into each other and break up.
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Corrasion is when destructive waves pick up beach material (e.g. pebbles) and hurl them at the base of a cliff. Over time this can loosen cliff material forming a wave-cut notch.
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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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Chemical weathering is the breakdown of rock through changing its chemical composition.
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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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When rainwater hits rock it decomposes it or eats it away. This is known as carbonation. This occurs when slightly acidic (carbonic) rain or seawater comes into contact with sedimentary rock, such as limestone or chalk, it causes it to dissolve. A chemical reaction occurs between the acidic water and the calcium carbonate and forms calcium bicarbonate. This is soluble and is carried away in solution. Carbonation weathering occurs in warm, wet conditions.
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Mechanical weathering is the breakdown of rock without changing its chemical structure (composition).
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The movement of sediment and beach material through wave action.
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Coastal transportation involves material being transported by the sea being deposited or dropped.
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Littoral drift
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Any three from:
- Waves enter an area of shallow water/waves enter a sheltered area, eg a cove or bay
- There is little wind
- A river or estuary flows into the sea reducing wave energy
- There is a good supply of material and the amount of material being transported is greater than the wave energy can transport.
Find out more about coastal deposition.
Beach material is suspended and carried by the waves.
Find out more about coastal tansportation.
