Also used in reference to the magmas from which these rocks crystallize. Mafic rocks are generally rich in iron and magnesium. Basalt and gabbro are examples of mafic rocks. (See felsic to contrast.)
Magma: ...
magma -- n. Molten rock generated within the Earth; forms intrusive (solidifies below the surface) and extrusive (solidifies above the surface) igneous rocks.
Magma, Mass, Mass Balance, Mass Movement, Mass Wasting, Meander, Medial Moraine, Melting, Meltwater, Metamorphism, Mid-Latitude Cyclone, Mineral, Moraine, Mountain Glacier, Mouth, ...
magma ocean A global-scale ocean of magma, according to some calculations several hundred kilometers deep, thought to have existed during the final stages of accretion as the Earth was forming.
Lavas (magmas that reach the surface) extrude not only from discrete individual volcanoes but from deep-reaching fractures in the crust that can tap into the upper mantle. The result is widespread flows covering large areas.
As the magma ocean cooled, it fractionally crystallized and differentiated, giving rise to a geochemically distinct crust and mantle.
It is a current project (Koning & al., 1995 ) developed within MAGMA group as an instance of its specific Multi-Agent approach, and implemented mostly in the JAVA language from SUN .
Some earthquakes are caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions.
 See also: Surface, Area, Region, Layer, Plate
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