What are metamorphic rocks?
Metamorphic rock is rock that has physically and chemically changed, or “morphed,” into new rock. The word “metamorphic” has its origins in classical Greek and means “to change form.” Rock of any type (sedimentary, igneous, or metamorphic) that is subjected to high pressure, high temperatures, and/or reactions with chemical solutions can be converted to metamorphic rock. This transformation can involve changes in a rock’s texture (grain size and shape), fabric (how the grains are oriented relative to one another), chemical composition, and mineral content. The rock remains solid as these changes occur. Through the process of metamorphism, the original rock, or protolith, changes into a new metamorphic rock. Metamorphic rock (left) compared with sedimentary rock (right). How are these high pressures and temperatures generated? The answer lies in the processes of plate tectonics. Plates that move against each other produce huge forces that create high pressures and temperatures that can
