Earth Science
Chapter 3
Section 5 and 6
A. How Metamorphic Rocks Form:
- Heat and pressure deep beneath the Earth’s surface can
change any rock into metamorphic rock.
- When rock material undergoes metamorphism, its
appearance, texture, crystal structure, and mineral
content changes.
- Metamorphic rock can form out of igneous,
sedimentary or other metamorphic rocks.
- Metamorphism takes place when rock material
undergoes great pressure from burial, intrusion of
magma into rock layers, or heat from the mantle.
- The heat and pressure changes minerals into other
minerals.
B. Classifying Metamorphic Rock:
- While under going great heat and pressure, the
tremendous pressure squeezes rock so tightly that the
mineral grains line up in flat, parallel bands or layers.
- Geologists classify metamorphic rocks by the
arrangement of the grains that make up the rocks.
- Rocks that have their grains arranged in parallel layers
or bands are said to be Foliated. These rocks split into
layers.
- Some examples of foliated rock are Slate, Schist and
Gneiss.
- Sometimes metamorphic rocks are nonfoliated- The
minerals are arranged randomly. These rocks do not
split into layers.
- Some examples of nonfoliated rock are marble and
quartzite.
Metamorphism of Rock Material:
Granite (Igneous) ------- Gneiss (Metamorphic)
Shale (Sedimentary) --------- Slate (Metamorphic)
Sandstone (Sedimentary) --------- Quartzite (Metamorphic)
Limestone (Sedimentary) -------- Marble (Metamorphic)
Gneiss and Slate (Metamorphic) -------- Schist (Metamorphic)
Section 6
C. The Rock Cycle:
- Force inside the Earth and at the surface produce a rock
cycle that builds, destroys and changes the rocks in the
crust.
See Rock Cycle Diagram: Page 95