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

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: GraniteAfter: Gneiss

Some examples… Before: ShaleAfter: 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