Igneous rock is formed when magma cools and solidifies, it may do this above or below the Earth's surface.
Magma can be forced into rocks, blown out in volcanic explosions or forced to the surface as lava.
The atoms and molecules of melted minerals are what make up magma.
These atoms and molecule rearrange themselves into mineral grains as the magma cools, forming rock as the mineral grains grow together.
There are over 700 different types of igneous rocks.
Examples of igneous rocks include basalt, granite, pumice, obsidian, tuff, diorite, gabbro and andesite.
Basalt forms the metamorphic rock granulite when subjected to extreme heat and pressure over time (metamorphism).
Granite is a common rock that contains at least 25% quartz and is sometimes used in construction because of its strength.
Pumice is an unusual, lightweight rock formed when molten rock is rapidly blown out of a volcano, forming bubbles as it quickly loses pressure and cools at the same time.
Obsidian is a volcanic glass that forms quickly without crystal growth, it can have very sharp edges making it useful as a cutting tool or arrowhead.
Tuff is a rock formed from volcanic ash.
The upper section of the Earth's crust is made up of around 95% igneous rock.
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