1. Title: Metamorphic Rocks Page #: 45 Date: 12/04/12
Table of Contents
Title: Metamorphic Rocks
Page #: 45
Date: 12/04/12

2. Objective Students will be able to recognize metamorphic rocks.
Students will be able to explain the processes by which rocks are metamorphosed.

3. Word of the Day
Metamorphosis: A change in form.

4. Recognizing Metamorphic Rocks
Metamorphic Rocks: Rocks that have been changed.
Metamorphic Rocks are pre-existing rocks that are exposed to increases in temperature and pressure, or hydrothermal solutions, that change the rock’s texture, mineral composition, or chemical composition.

5. Recognizing Metamorphic Rocks
Increases in temperature and pressure do not melt the rock, but they do change it.
High temperatures come from Earth’s interior.
Rocks are either buried or located near igneous intrusions (magma pockets.)
High pressures come from deep burial or from compression during mountain building.

6. Recognizing Metamorphic Rocks
Metamorphic Minerals - Metamorphism changes minerals that are present in rock to new minerals - “solid state alterations.”
Specific minerals are associated with specific conditions during metamorphosis.

7. Recognizing Metamorphic Rocks
Metamorphic Textures:
2 Kinds:
Foliated: Layers and bands or minerals (stripes.)
Bands always form perpendicular to pressure.
Example: Gneiss - formed from granitic rock.
Nonfoliated: Minerals that form blocky crystal shapes.
Examples: Quartzite - formed from quartz rich sandstone.
Marble - formed from limestone.

8. Recognizing Metamorphic Rocks
Quartzite - Nonfoliated
Gneiss - Foliated

9. Recognizing Metamorphic Rocks
Porphyroblasts: Large crystals that have grown in solid rock. Surrounded by smaller crystals.
Example: Garnet