magma

WHAT IS MAGMA?

Magma is molten rock under the earths surface. Molten rock above the surface is called lava. Magma is created when rocks are at the correct temerature and pressure to cause melting. Also known as passing the liquidus. Magma is also created from the subduction of, cold, dense lithosperic plates into the hot rock of the mantle. The water in the subduction slab lubricates the rock and lowers the liquidus causus the melting of rocks, thus creating rising plume of magma to the crust. Magma is created in another way in massive quantities at divergent plate boundries. Known as mid-ocean ridges. Where decompression melting of mantle rock occurs where the crust is being removed from the mantle.