rocks

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Rocks are formed when magma rises, then cools and solidifies to form igneous rocks. This may occur on the Earth's surface or within the Earth's crust (intrusive or extrusive crystallisation).

Igneous rocks may be destroyed/broken down by weathering and erosion (denudation) into sediments.

The sediments are transported by moving water, ice and wind.

Rocks are reconstituted where sediments are compressed, compacted, and cemented under the weight of water to form sedimentary rocks (lithification). They form layers known as strata.

Sedimentary rocks may be changed/modified by great heat and pressure to form metamorphic rocks.

Igneous rocks may also be changed by heat and pressure to form metamorphic rocks.

Metamorphic rocks may be broken down into sediments by weathering and erosion.

All rock types are destroyed at subduction zones where they melt back into the mantle.

The cycle continues.

ROCKS ARE GROUPED ACCORDING TO THEIR FORMATION

Igneous Magma/lava cools e.g. basalt, granite

(Latin for fire) and becomes solid pumice

Sedimentary When sediments e.g. limestone, coal

(plants, remains of sandstone, shale

animals, rocks), conglomerate

accumulate, compress,

compact, and cement

into a solid.

Metamorphic When a rock is e.g. marble, quartzite