ROCKS~METAMORPHIC ROCKS

FORM AS EXISTING ROCKS CHANGE~

Metamorphic core of the Himalayan Mountains

http://www.videojug.com/film/geology-metamorphic-rockshttp://www.youtube.com/watch?v=kRUwchlza88

Vocabulary METAMORPHISM

The process of a rock changing by heat or pressure—or both.

RECRYSTALLIZATIONHeat and pressure break

the bonds that join atoms in minerals. Then the atoms join differently, making new minerals.

FOLIATIONMinerals

arranged in flat

or wavy parallel

bands

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.

How Rocks Change…

Metamorphic rocks form as existing rocks go through metamorphism –heat and pressure

Increasin

g H

eat & P

ressure

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.

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.

5. Deep within the crust, schist changes to gneiss. Recrystallization separates light and dark minerals.

shale

slate

phyllite

schist

gneiss

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 ofkilometers wide and deep.• Mountain ranges can be made.

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.

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.

Rocks in the World Around Us