1. Rocks ~metamorphic rocks form as existing rocks change~
Metamorphic core of the Himalayan Mountains

2. Vocabulary FOLIATION Minerals arranged in flat or wavy parallel
bands
METAMORPHISM
The process of a rock changing by heat or pressure—or both.
RECRYSTALLIZATION
Heat and pressure break the bonds that join atoms in minerals. Then the atoms join differently, making new minerals.

3. Heat and Pressure Changes Rocks
Pressure causes minerals to
flatten out in one direction.
Heat and pressure break
bonds between atoms, and
recrystallization occurs.
The higher the temperature
and pressure, the greater the
changes.

4. Increasing Heat & Pressure
How Rocks Change…
shale
Increasing Heat & Pressure
1. Sedimentary rock, like shale, can be buried when pushed into the crust.
2. Shale changes to slate as pressure causes the minerals to line up in layers.
slate
phyllite
3. Slate changes to phyllite deeper in the crust with higher heat/pressure.
4. With even more heat and pressure, phyllite changes into schist and new minerals are formed.
schist
5. Deep within the crust, schist changes to gneiss. Recrystallization separates light and dark minerals.
gneiss
Metamorphic rocks form as existing rocks go through metamorphism –heat and pressure

5. Metamorphic Changes Over Large Areas
Change occurs over large areas when BOTH temperature and pressure forces are high.
Rocks are buried, pressed together, and broken apart.
Occurs over 1,000’s of
kilometers wide and deep.
Mountain ranges can be
made.

6. Metamorphic Changes Over Small Areas
Change occurs over small areas with high temperature OR high pressure.
Heat from lava or magma can cause rocks to recrystalize.
Pressure can cause rocks to move and grind past each other.
Earthquakes can occur.

7. Foliated & Nonfoliated Rocks
Foliation develops when rocks are under pressure.
Foliation is common in rocks that have changed over large areas.
If a rock is made of mainly one mineral, it is nonfoliated. There are no minerals to separate and line up in layers. Marble and quartzite are examples of this.

8. Rocks in the World Around Us