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20 October 2014
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Rivers and Coasts Rivers and Coasts

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What is a coast?

The water cycle

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How do Coasts Change?

When the energy of the sea or waves is high (with big waves and rough seas), boulders and large pebbles can be moved. When the energy is low (with small waves), only sand can be moved.
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Waves have the power to erode, or break up, and wear away rocks over time. Storm, or high-energy, waves breaking at the foot of a cliff dislodge blocks of stone - rocks. Waves fling pebbles at the foot of a cliff and wear the cliff away. This process is abrasion.

The broken rocks get moved around on the beach and are rounded and worn down smaller.

This way pebbles, and eventually sand, are made.


Where rock pieces move against another rock and wear it away, e.g. a pebble is washed against a cliff by waves and breaks off tiny bits of the cliff. If you rub two pebbles together you will have abrasion and the pebbles will begin to be worn away. You can try it with two pieces of chalk. Abrasion will cause them to crumble to powder.

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