Contact Metamorphism

Deep underground, zones of metamorphism form around the hot magma of batholiths. Click on image for full size (18K GIF) L.Gardiner/Windows Original

Rocks that are in contact with hot magma or lava often become metamorphosed. This is called contact metamorphism.

Contact metamorphism can either happen deep underground or at the Earth's surface. Underground, hot magma, fills areas within the crust; large areas are called batholiths. The hot magma alters the surrounding rocks. The amount of rock that is changed depends on how much magma there is producing heat. The zone of altered rock around a batholith is called an aureole and it may cover more than 100 square kilometers of land. Above ground, lava erupting from a volcano alters the rock that it erupts onto.

Metamorphism of rocks that happens over larger areas is called regional metamorphism.