1. Heat: Igneous rocks are buried deep within the Earth, exposed to immense heat from the Earth's mantle. This heat causes the atoms and molecules within the rock to vibrate faster and rearrange themselves.
2. Pressure: The immense weight of overlying rocks creates immense pressure on the igneous rock. This pressure can cause the rock to deform and recrystallize.
3. Fluids: Hot, chemically-rich fluids often circulate through the rocks in the Earth's crust. These fluids can react with the minerals in the igneous rock, altering their composition and structure.
4. Recrystallization: The combination of heat, pressure, and fluids causes the minerals within the igneous rock to change. Existing minerals may be rearranged or break down, and new minerals can form. This process is called recrystallization.
5. Texture and Structure: The resulting metamorphic rock will have a different texture and structure than the original igneous rock. For example, igneous rocks often have a coarse-grained texture, while metamorphic rocks may have a foliated (layered) texture or a non-foliated texture depending on the pressure and heat conditions.
Examples of Metamorphic Rocks:
* Marble: Formed from the metamorphism of limestone.
* Slate: Formed from the metamorphism of shale.
* Gneiss: Formed from the metamorphism of granite or other igneous rocks.
Important Note: Metamorphism is a solid-state process. It does not involve melting, unlike the process of igneous rock formation. The minerals within the rock change without completely melting and reforming.
