What are Metamorphic Rocks?
Metamorphic rock is the result of the transformation of an existing rock type through the process of metamorphism.
These rock types have been subjected to intense heat and pressure which causes a profound physical and/or chemical change in their composition.
Despite the amount of heat they're exposed to, instead of melting they're transformed into a denser more compact type of rock.
If the rocks were exposed to enough heat to cause them to melt, once the material solidified it would be an igneous rock.
Before being metamorphosed metamorphic rock would have either been an igneous or sedimentary rock.
When the chemical composition of a rock changes new minerals are created.
Movement in the Earth causes the heat and pressure required to create a metamorphic rock.
Marble which is one example began life as limestone. Lapis lazuli is also a metamorphic rock.
The metamorphic rock in our photo is marble. Courtesy of Stan Celestian. The image is clikable and redirects to the original photo.