Making new rocks from old

Part of Hall of Planet Earth.

Making New Rocks From Old AMNH/R.Mickens

Metamorphism is the process by which rocks re-crystallize into new combinations of minerals in response to changing temperature, pressure, and exposure to hot, reactive fluids. The rocks’ texture and grain size are usually altered as well. Metamorphic rocks are created deep in the roots of mountains. Geologists study these rocks to learn more about mountain building and how the Earth’s crust evolves.