All Metamorphic Rock starts off as Igneous or Sedimentary Rock Geologists are always interested in...

Metamorphic Rocks

Heat and Pressure

Metamorphic Rocks are created out of old rocks by HEAT

and PRESSUREBut, they don’t melt (if they did, they would be

igneous).

All Metamorphic Rock starts off as

Igneous or Sedimentary Rock

Geologists are always interested in what kind of rock a metamorphic rock used to be. However, if extreme deformation has occurred, this can be quite difficult.

Heat and Pressure As you go deeper into

the earth, it becomes HOTTER and HOTTER

As you go deeper into the earth, there is more and more PRESSURE because there is more rock above you.

Heat and Pressure Heat makes rock more

MALLEABLE (more bendy)

Pressure DEFORMS rock by compacting it, stretching it, or twisting it.

Together HEAT and PRESSURE change the composition of the old rock

Remember: Metamorphic rock never melted (or else it would be igneous)

Foliation

Foliation occurs when a rock is squeezed and shortened by extreme pressure to form bands and layers

However, foliation does not always happen. There are both foliated and non-foliated metamorphic rocks

Let’s see it in action…

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0607/es0607page01.cfm?chapter_no=

visualization

Two types of Metamorphism Regional

When metamorphism happens to an extensive (big) REGION of rock

This can happen when two masses of rock collide, or when rock is pushed deep underground

Two types of Metamorphism

Contact

Contact Metamorphism happens when rock comes in CONTACT with hot magma (but does not melt itself).

This can happen at the surface or underground and only happens to a small amount of rock

Where are metamorphic rocks

found? Metamorphic rocks can be created out of

any type of rock and are thus very hard to classify.

However, because metamorphosis is caused by extreme HEAT and PRESSURE, metamorphic rocks are usually found where something extreme has happened (like volcanic activity or two plates colliding)

Some examples…Before: Granite After: Gneiss

Some examples…Before: Shale After: Slate

Some examples…Before:

LimestoneAfter: Marble

Metamorphic Rock… Is created out of old rock by heat and

pressure

Doesn’t melt (or else it would be igneous rock)

Is often foliated/deformed by extreme pressure

Formed by regional or contact metamorphism