Magma

Magma (Plurals: magmas and magmata) is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. Magma may contain suspended crystals and gas bubbles. By definition, all igneous rock is formed from magma.

Magma is a complex high-temperature fluid substance. Temperatures of most magmas are in the range 700°C to 1300°C, but very rare carbonatite melts may be as cool as 600°C, and komatiite melts may have been as hot at 1600°C. Most are silicate solutions.

It is capable of intrusion into adjacent rocks or of extrusion onto the surface as lava or ejected explosively as tephra to form pyroclastic rock.

Environments of magma formation and compositions are commonly correlated. Environments include subduction zones, continental rift zones, mid-oceanic ridges, and hotspots, some of which are interpreted as mantle plumes. Environments are discussed in the entry on igneous rock. Magma compositions may evolve after formation by fractional crystallization, contamination, and magma mixing.