The formation of igneous rocks from magma 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.