Types of Rock

Igneous rock

- Forms when molten magma/ lava cools and solidifies. 

- If it's cooled on the surface it has small crystals, like basalt. 

- If it cooled underground it has large crystals, like granite. 

Sedimentary rock

- Forms when sediment (tiny particles) settle on the ocean floor and the layers build up. The pressure causes the layer to harden.

- Chalk and limestone, made from shells of sea creatures that fell to the ocean floor.

Metamorphic Rock

- Formed from sedimentary rock thats come under heat and pressure underground. This makes the arrangement of crystals in the rock change. 

- Limestone and chalk change to marble when they come under heat and pressure.

Rate of cooling affects the crystal size of igneous rocks. 

- Intrusive igneous rock cools slowly underground because it is insulated by the surronding rocks. Forms large crystals.

- Extrusive igenous rock cools quickly above ground. Forms small crystals. 

Crystals are formed by atoms fitting together in rigid structures with regular lines and layers.

- The amount of kinetic energy in atoms is related to their temperature.

- As molten rock cools, the amount of energy in particles reduces. They bond to make crystals. 

- If cooling is slow, the amount of crystals is small but they are large.

- If rapid, vast amounts are made, but they are small.