Magma: Mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth

The liquid rock may have solid bits mixed in with it, and volcanic gas.

There are different types of magma. One is called felsic magma. Felsic magma is thick and has silica minerals. It mostly makes light-coloured rocks. Another type is called mafic magma, which is runny and has less silica. It usually makes dark-coloured rocks. Magmas can be intermediate between both types.

Magma may become solid by cooling slowly below the surface. This makes "plutonic" rocks such as granite. When magma comes out from the ground in a volcano it is called lava. Lava cools quickly, and forms other kinds of rock such as basalt.

Magma is produced by melting of the Earth's mantle or the crust. It happens at tectonic settings, such as subduction zones, continental rift zones, mid-ocean ridges and hotspots.

Melted material from the mantle and crust moves up through the crust and collects in magma chambers.

When they come up through the crust, magmas may feed a volcano and come out as lava. But they may solidify underground to form an intrusion (magma which cools and becomes solid). Intrusions eventually cool down and become igneous dikes or sills.

The study of magma is usually done in lava flows. However, magma was found under the ground three times in geothermal drilling projects—twice in Iceland and once in Hawaii.