The Online Encyclopedia and Dictionary







This article is about the type of molten rock. For other meanings of magma, see Magma (disambiguation).

Magma is molten rock often located inside a magma chamber beneath the surface of the Earth. Magma is a complex high-temperature silicate solution that is ancestral to all igneous rocks, both intrusive and extrusive. Magma exists between 650 and 1200 degrees C. Magma is under high pressure and sometimes emerges through volcanic vents in the form of flowing lava and pyroclastic ejecta. These products of a volcanic eruption usually contain dissolved gases which have never before reached the planet's surface. Magma collects in many separate magma chambers within the Earth's crust, and will have slightly different compositions in different places.

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