Swash

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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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Weak swash, strong backwash.

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Destructive 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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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.

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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The wearing away of land by the sea.

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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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Mechanical weathering is the breakdown of rock without changing its chemical structure (composition).

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

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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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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 bounced along the seafloor.

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Material is dissolved and carried by the water.

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Longshore drift

Find out more about longshore drift.

Beach material is suspended and carried by the waves.

Find out more about coastal tansportation.