The temperature is very high where magma forms, which is why it is melted. When the magma cools underneath the surface of the earth it is called plutonic rock. Magma can also cool at the surface of the earth when pressure builds up inside the earth and it is forced through a volcano. This is called lava . Metamorphic rocks are changed rocks.
Any rock can become a metamorphic rock if a lot of heat and pressure is applied to it.
This change occurs because minerals in the rock react with each other as a result of the added heat and pressure. This metamorphosis always takes place deep below the surface of the earth. Sometimes metamorphic rocks are exposed due to the erosion of the rock lying on top of them. This document has been accessed 15,161 times since November 14, 1996.