Constructive waves

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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.

Find out more about constructive waves and destructive waves.

Constructive wave

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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.

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Corrasion, abrasion, hydraulic action, attrition and corrosion/solution.

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.

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Coastal erosion is the wearing away of the land by the sea.

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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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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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Chemical weathering is the breakdown of rock through changing its chemical composition.

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Weathering is the breakdown of rock in situ by the action of rainwater, extremes of temperature, and biological activity.

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Traction – large pebbles and boulders are rolled along the seafloor.

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Wave energy reduces leading to material being deposited.

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Beach material is suspended and carried by the waves.

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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.

Solution, suspension, saltation and traction.

Find out more about coastal transportation.