Magma Magma Magma (from Ancient Greek μάγμα ("mágma") meaning "thick unguent") is the molten or semi-molten natural material from which all igneous rocks are derived. 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
Magma (the extrusive equivalents of gabbro, diorite and granite, respectively). During a volcanic eruption the magma that leaves the underground is called lava. Lava cools and solidifies relatively quickly compared to underground bodies of magma. This fast cooling does not allow crystals to grow large, and a part of the melt does not crystallize at all, becoming glass. Rocks largely composed of volcanic glass include obsidian, scoria and pumice. Before and during volcanic eruptions, volatiles such as CO and HO partially leave the melt through a process known as exsolution. Magma with low water content becomes increasingly viscous. If massive exsolution