Magma (from Ancient Greek (mágma) meaning "thick unguent") is the molten or semi-molten natural
material from which all igneous rocks are formed. Magma is found beneath the
surface of the Earth, and evidence of magmatism has also been discovered on
other terrestrial planets and some natural satellites. Besides molten rock,
magma may also contain suspended crystals and gas bubbles. Magma is produced by
melting of the mantle and/or the crust at various tectonic settings, including
subduction zones, continental rift zones,mid-ocean ridges and hotspots. Mantle
and crustal melts migrate upwards through the crust where they are thought to be
stored in magma chambers or trans-crustal crystal-rich mush zones. During their
storage in the crust, magma compositions may be modified by fractional
crystallization, contamination with crustal melts, magma mixing, and degassing.
Following their ascent through the crust, magmas may feed a volcano or solidify
underground to form an intrusion (e.g., an igneous dike or a sill). While the
study of magma has historically relied on observing magma in the form of lava
flows, magma has been encountered in situ three times during geothermal
drilling projects—twice in Iceland (see Magma usage for energy production), and
once in Hawaii.
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