What is metamorphism?
Metamorphism is a process whereby existing rocks are transformed or metamorphosed by heat and pressure to form new rocks, stable at those new temperature and pressure conditions. For example, limestone can be metamorphosed to marble, shale to slate, and sandstone to quartzite. With increased temperature, schists and gneisses may form from these and other original rocks. Metamorphic rocks preserve evidence of the original source rocks in preserved chemical and physical features and of the conditions of metamorphism in the minerals and new structures in the transformed rock. Metamorphism is a key process in mountain building and a major evidence of colliding tectonic plates.
