What is a metamorphic rock?

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (150 megapascals (1,500 bar)) [clarify], causing profound physical or chemical change. read more

metamorphic rock in Culture metamorphic rock Rock that was once one form of rock but has changed to another under the influence of heat, pressure, or some other agent without passing through a liquid phase. read more

Metamorphic rocks are created by the physical or chemical alteration by heat and pressure of an existing igneous or sedimentary material into a denser form. read more