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Where do the rocks come from?

We get many useful substances from rocks, such as building materials, metals, pigments and jewels. But where do we get the rocks themselves from?

They come from the Earth’s crust. The Earth’s crust is the thin outer layer of the Earth. It is about 30 km thick on land and only about 8 km thick under the sea.

crust

mantle

inner core

outer core

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Types of weathering

Which type of weathering is caused by each of these:

temperature change

acid rain

plants and animals?

There are three types of weathering:

physical weathering

biological weathering

chemical weathering.

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Physical weathering

Physical weathering occurs when rock is broken down into smaller pieces by the effects of temperature and water.

Exfoliation weathering (or ‘onion-skin’ weathering) is caused by very hot weather.

Freeze-thaw weathering is caused by the melting and freezing of water.

Exfoliation and freeze-thaw weathering tend to occur in very different types of landscapes.

Which type of weathering do you think will primarily occur in the desert, and which will occur in the mountains?

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Exfoliation weathering in action

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Freeze-thaw weathering in action

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Plants and weathering in action

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Erosion

As a rock is weathered, pieces of it fall off. This is called erosion. They will then be transported away by water, wind or glaciers.

by water by wind by glacier