Coastal Landscapes

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How are waves formed?

- They're formed when the wind blows over the sea. This causes friction on the surface of the water and causes ripples to form. These develop into waves.

-They can also be formed when earthquakes or volcanic eruptions shake the seabed. These are called Tsunamis.

What happens when waves reach the coast?

- Only when waves approach shore is there forward movement of water as waves break and surge up the beach.

- The seabed interrupts the circular movement of the water. As the water becomes shallower, the circular motion becomes more elliptical. This causes the crest of the wave to rise up and eventually to collapse on the beach. The water that rushes up the beach is called the swash. The water that flows back to sea is called the backswash.

Types of waves

- Constructive waves - These are low waves that surge up the beach and 'spill' with a powerful swash. They carry and deposit large amounts of sand and pebbles and 'construct' the beach making it more extensive. Surfers prefer constructive waves because they give longer rides. These waves are formed by storms often hundreds of kilometres away.

- Destructive waves - These are formed by local storms close to the coast, and they can 'destroy' the beach - hence their name. They are closely spaced and often interfere with each other producing a chaotic swirling mass of water. They become and steep before plunging down onto the beach. There is little forward motion when a destructive wave breaks but a powerful backwash. This explains the removal of sand and pebbles and the gradual destruction of the beach.

What causes cliffs to collapse?

Cliffs collapse because of different types of weathering. This is the weakening or decay of rocks in their original place on, or close to, the ground surface. It is mostly caused by weather factors such as rainfall and changes in temperature.

Types of weathering:

- Mechanical (physical) weathering - the disintegration of rocks. Where this happens, piles of rock fragments called scree are found at the foot of cliffs.

- Chemical weathering - Caused by chemical changes. Rainwater, which is slightly acidic, very slowly dissolves certain types of rocks and minerals.

- Biological weathering - Due to actions of flora and fauna. Plant roots grow in cracks in rocks. Animals such as rabbits burrow into weak rocks such as sands.

What are the processes of mass movement?

Mass movement is the downward movement or sliding of material under the influence of gravity. In 1993, 60m of cliff slipped onto the beach near Scarborough in North Yorkshire taking with it part of the Holbeck Hall Hotel. The hotel was left on the cliff edge and had to be demolished.

Coastal deposition

Coastal deposition takes place in areas where the flow of water slows down. Waves lose energy in sheltered bays and where water is protected by spits or bars. Here sediment can no longer be carried or moved and is therefore deposited. This explains why beaches are found in bays, where the energy of waves is reduced. This is called wave refraction.