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Thermal or Contact Metamorphism

• Thermal or contact metamorphism occurs in rocks when they are intruded by an hot magma which could take the form of a batholith. The hot magma 'bakes' the surrounding rocks causing the rock to change into a metamorphic rock. A good example of contact metamorphism would be limestone into marble.
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• Caption: Thermal (contact) metamorphism diagram

Regional Metamorphism

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• Caption: Regional metamorphism diagram
• Regional metamorphism occurs over wide areas of land, deep within the Earth. The pressure and heat within the Earth changes the mineral and sediment compositions in the rock and therefore the sedimentary rock changes into a new, different metamorphic rock. A good example of regional metamorphism would be sandstone into schist. The new rocks often have coarse grains.