Metamorphic rocks form from the changes in mineral composition and texture of existing rocks subjected to high temperatures and pressures within the Earth. There are two main types of metamorphism: contact metamorphism, caused by heat from nearby magma, and regional metamorphism, associated with large-scale mountain building. Metamorphic rocks exhibit either a layered, foliated texture or a nonfoliated texture without visible bands.

1. Metamorphic Rocks 3.4

2. Metamorphism The changes in mineral composition and texture of a rock subjected to high temperature and pressure within Earth.

3. Contact Metamorphism Changes in a rock caused by the heat from a nearby magma body.

4. Regional Metamorphism Metamorphism associated with large-scale mountain-building processes.

5. Hydrothermal Solution The hot, watery solution that escapes from a mass of magma during the later stages of crystallization; such solutions may alter the surrounding rock.

6. Foliated Metamorphic Rock A metamorphic rock with a texture that gives the rock a layered appearance

7. Nonfoliated Metamorphic Rock Metamorphic rock that does not exhibit a banded or layered appearance.

8. Key Concept Where does most metamorphism take place? Most metamorphic changes occur at elevated temperatures and pressures. These conditions are found a few kilometers below Earth’s surface and extend into the upper mantle.

9. Key Concept How is contact metamorphism different from regional metamorphism? Contact metamorphism hot magma moves into rock and Regional metamorphism results in large-scale deformation and high-grade metamorphism.

10. Key Concept What are three agents of metamorphism, and what kinds of changes does each cause? The agents of metamorphism are heat, pressure, and hydrothermal solutions.

11. Key Concept How are metamorphic rocks classified? They are classified by their texture.