Definition - What does Metamorphic Rock mean?
A Metamorphic Rock is a rock that is formed after an existing rock is transformed by pressure, stress or heat causing profound physical and chemical change deep within the crust. The process of transforming existing rock types into Metamorphic Rocks is called metamorphism. For example, shale, a sedimentary rock of clay particles, can be transformed by heat and pressure in to a hard metamorphic slate rock. Marble is a good example of a metamorphic rock.
Petropedia explains Metamorphic Rock
A Metamorphic Rock is formed when the earth movements cause a rock to be squeezed or deeply buried which as a result creates a lot of heat, great pressure and stress on sedimentary and igneous rocks. The minerals contained in the rock are changed chemically due to the high pressure and temperature resulting in the formation of the Metamorphic Rock. At times, Metamorphic Rocks are also formed when sedimentary or igneous rocks are close to molten magma because of the high heating temperature.