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Photo glossary of volcano terms

Sketch of a magma reservoir and conduit beneath a volcano

Sketch by B. Myers

Sketch of a magma reservoir beneath a volcano and a conduit leading up to a lava dome at the surface. Arrow indicates direction of magma movement from a deeper source.

Magma
Magma is molten or partially molten rock beneath the Earth's surface. When magma erupts onto the surface, it is called lava. Magma typically consists of (1) a liquid portion (often referred to as the melt); (2) a solid portion made of minerals that crystallized directly from the melt; (3) solid rocks incorporated into the magma from along the conduit or reservoir, called xenoliths or inclusions; and (4) dissolved gases.

 

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U.S. Department of the Interior, U.S. Geological Survey, Menlo Park, California, USA
URL http://volcanoes.usgs.gov/Products/Pglossary/magma.html
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Last modification: Monday, 04-Sep-2000 22:44:27 EDT (SRB)