The rock cycle - Metamorphic rocks

Metamorphic rocks are the third type we'll look at. They formed from other rocks that are changed because of heat or pressure.

Formation

Earth movements can cause rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under great pressure. They do not melt, but the minerals they contain are changed chemically, forming metamorphic rocks.

Sometimes, metamorphic rocks are formed when rocks are close to some molten magma, and so get heated up.

Metamorphic rocks may form from rocks heated by magma

Remember that metamorphic rocks are not made from melting rock. (Rocks that do melt form igneous rocks instead.)

What are metamorphic rocks like?

When a metamorphic rock is formed under pressure, its crystals become arranged in layers. Slate, which is formed from shale, is like this. Slate is useful for making roof tiles because its layers can be split into separate flat sheets.

Marble bedrock on the coast.

Marble is another example of a metamorphic rock. It is formed from limestone.

Metamorphic rocks sometimes contain fossils if they were formed from a sedimentary rock, but the fossils are usually squashed out of shape.

Metamorphic rocks can be formed from any other type of rock - sedimentary or igneous. Remember these two examples of common metamorhpic rocks and where they come from:

• slate is formed from shale

• marble is formed from limestone

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