The formation of igneous rocks from magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

is known as Magmatism.

Magmatism is a process responsible for mountain formation. The process of magmatism produces an additional mass and volume to the Earth’s surface. For example the formation of volcanoes or island arcs at convergent plate boundaries. Or mid-ocean ridges and therefore ocean-floor spreading at divergent plate boundaries.
Magmas form by partial melting of silicate rocks either in Earth's mantle, the continental or the oceanic crust.
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