Types of Rocks

Igneous

Sedimentary

Metamorphic

Igneous rocks are the most common rock type found on Earth.

They are formed when magma from the mantle rises to the surface, cools and hardens.

All igneous rocks contain crystal with size dependent on how quickly the magma cooled.

Examples of Igneous rock include granite and pumice.

Sedimentary rocks form under the seas and oceans.

They form when things like sand, rock, pieces of sea creatures are carried by rivers into the seas and oceans and is deposited at the bottom of the ocean floor.

The weight of the sediments squeezes down on the previous layer and squeezes out the water which allows salt crystals to form (COMPACTION). The crystals help to glue all the sediment together, forming a rock. (CEMENTATION).

Metamorphic rocks are formed by pressure or heat under the surface.

They are formed from igneous and sedimentary rocks which can be heated under the surface of the earth.

The heating of these rocks puts them under huge pressure and the crystals become arranged in layers.

Slate and marble are possibly the most well known metamorphic rocks.

Slate is formed from shale, while marble is formed from limestone.

Others include: quartzite formed from sandstone and granulite formed from basalt.