Wave Action
The size of a wave depends on its fetch. The fetch is the distance a wave travels. The greater the fetch, the larger the wave. Wind also has a significant effect on the size of waves. The stronger the wind the larger the wave.
As a wave approaches a beach it slows. This is the result of friction between the water and the beach. This causes a wave to break.
![[image - wave]](../images/coast/waves.gif)
There are two main types of wave:
![[image - constructive waves]](../images/coast/constructivewaves.gif)
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The video above shows constructive waves. If you cannot view the video please ensure you have the latest version of Windows Media Player installed on your computer. You can download it here. Alternatively download the original file here. |
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Destructive waves destroy beaches. The waves are usually very high and very frequent. The back wash has less time to soak into the sand. As waves continue to hit the beach there is more running water to transport the material out to sea. these waves are most common in winter.
![[image - destructive waves]](../images/coast/destructivewaves.gif)
There are four main processes which cause coastal erosion. These are corrasion/abrasion, hydraulic action, attrition and corrosion/solution.
Corrasion/abrasion is when waves pick up beach material (e.g. pebbles) and hurl them at the base of a cliff.
When waves hit the base of a cliff air is compressed into cracks. When the wave retreats the air rushes out of the gap. Often this causes cliff material to break away. This process is known as hydraulic action.
Attrition is when waves cause rocks and pebbles to bump into each other and break up.
Corrosion/solution is when certain types of cliff erode as a result of weak acids in the sea.
You can view animations of each of these processes here.
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