Rocks

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Rocks

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Rocks

There are 3 types of rocks.

Igneous, metamorphic and sedimentary.

Some rocks have air bubbles because of the way they are formed.

Rocks such as Millstone Grit have these properties and are otherwise known as Sedimentary Rocks

Other rocks don’t have air bubbles, these tend to have crystals

Crystals have a more jagged form (meaning they fit together more easily)

This means there’s less air bubbles therefore its a denser rock

Metamorphic and Igneous rocks have these properties.

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Metamorphic

Metamorphism means "changed form".

The Changes occur because of:

Heat

Pressure

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How metamorphic rocks change

Say a sedimentary rock is pushed down towards the earth’s mantle

The magma heats it up and changes its structure

Also the pressure can take part in this process.

The pressure comes from rocks above and they get pushed down.

So the texture, mineral structure and physical properties all change

However, they have the same because they have the same chemical compounds.

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Sedimentary Rocks

For thousands, even millions of years, little pieces of our earth have been eroded

broken down and worn away by wind and water

These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans

Layer after layer of eroded earth is deposited on top of each

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Continued .

These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.

The weight of all the layers squeezes out most of the water from the sediment

Chemicals in the water cement the bits of sand and mud together

A new sedimentary rock has formed !

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Igneous Rocks

Igneous rocks are formed .

When molten rock (magma) is pushed up from beneath the earth’s crust

It cools to form solid rock

Properties

They contain crystals and they are hard

There are two types of igneous rock

Intrusive and extrusive

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Continued .

Intrusive igneous rocks have cooled slowly in the earth’s crust

They have large crystals

Extrusive igneous rocks cool quickly