1. Earth Science
Metamorphic rock

2. Objectives: Describe two ways a rock can undergo metamorphism.
Explain how the mineral composition of rocks changes as the rocks undergo metamorphism.
Describe the difference between foliated and non-foliated metamorphic rock.

3. Origins of Metamorphic Rock
Metamorphic rocks
Rocks in which the structure, texture, or composition of the rock have changed
All three types of rock can be changed by heat, pressure, or a combination of both
A rock’s texture or mineral composition can change when its surroundings change
If the temperature or pressure of the new environment is different from the one in which the rock formed
the rock will undergo metamorphism

4. Regional metamorphism
Contact metamorphism
When magma moves through the crust, the magma heats the surrounding rock and changes it.
Regional metamorphism
occurs when pressure builds up in rock that is buried deep below other rock formations
or when large pieces of the Earth’s curst collide with each other.

5. Composition of Metamorphic Rock
As rocks undergo metamorphism
Original minerals in a rock change into new minerals that are more stable in the new pressure and temperature conditions.
Index minerals (form only in metamorphic rock)
Are used to estimate
Temperature
Depth
Pressure ---- at which a rock undergoes metamorphism.
calcite + + +
Heat and Pressure =
quartz
hematite
Garnet

6. Texture of Metamorphic Rock
Two types:
Foliated Metamorphic Rock
Mineral grains are arranged in planes or band
Nonfoliated Metamorphic Rock
Mineral grains are not arranged in planes or band
commonly made of one or only a few minerals.

7. This shows what happens to shale, a sedimentary rock, when it is exposed to more and more heat and pressure.
Slate
Shale
Phylite
Gneiss
Schist

8. Two examples of nonfoliated metamorphic rock
undergoes
metamorphism
limestone
Marble
undergoes
metamorphism
Sandstone
Quartzite

9. Metamorphic Rock Structures
Metamorphic rock has features that indicates its history. These features are caused by deformation:
Change in the shape of a rock caused by a force placed on it.
These forces may cause a rock to be squeezed or stretched.