coasts

Coasts are shaped by the sea and the action of waves. The processes that take place are erosion, transportation and deposition.

The size and energy of a wave is influenced by:

how long the wind has been blowing

the strength of the wind

how far the wave has travelled (the fetch)

When a wave breaks, water is washed up the beach  

After the swash the water runs back down the beach 

With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger than the swash.

·         Destructive waves are created in storm conditions.

·         They are created from big, strong waves when the wind is powerful and has been blowing for a long time.

·         They occur when wave energy is high and the wave has travelled over a long fetch.

·         They tend to erode the coast.

·         They have a stronger backwash than swash.

·         

• ·         They are created in calm weather and are less powerful than destructive waves.
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• ·        They break on the shore and deposit material, building up beaches.
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• ·         They have a swash that is stronger than the backwash.

Coastal erosion is the wearing away and breaking up of rock along the coast. Destructive waves erode the coastline in a number of ways:

• Hydraulic action. Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
• Abrasion. Bits of rock and sand in waves grind down cliff surfaces like sandpaper.
• Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
• Solution. Acids contained in sea water will dissolve some types of rock such as chalk or limestone.

There are various sources of the material in the sea. The material has been:

• eroded from cliffs
• transported by longshore drift along the coastline
• brought inland from offshore by constructive waves
• carried to the coastline by rivers