Metamorphic Rocks

Metamorphic rocks are formed when other rocks are forced into the Earth where they heat up, become pliable, twist and fold and are under extreme pressure.  Superheated and reactive fluids can also metamorphose rocks. Sometimes meteorites hit the ground so hard that they too can change rock. The word "morph" means to change, just like a metamorphosed caterpillar is a butterfly.  

There are two types of metamorphic rock textures: foliated and non-foliated.  Foliated rocks occur when the mineral grains are aligned parallel.  Non-foliated rocks do not have aligned mineral grains.

Foliated Metamorphic Rock


Non-Foliated Metamorphic Rock

All metamorphic rocks have what is referred to as a parent rock.  The parent rock is the rock from which the metamorphic rock came from.  For example quartzite came from the sedimentary rock sandstone.  As sandstone is driven deep into the Earth its mineral grains were squeezed and out comes quartzite.  Below is an image of some parent to metamorphic rock configurations.

Metamorphic Parent Rocks

There are also two types of metamorphism: contact and regional.  Contact metamorphism occurs adjacent to magma bodies.  It occurs because the magma is supplying the heat to nearby rock to make them pliable.  Meteorites also cause contact metamorphism when the meteorite slams into the ground. Regional metamorphism occurs in very large scale areas, like mountain ranges.  As mountain ranges are being formed, big blocks of rocks call plates slam into each other creating the pressure and generating the heat to bend and fold rocks causing mineral grains to realign.

contact metamorphism

Regional Metamorphism

Using the internet or other resources fill out the table and answer the questions in the following assignment.

SUSD5 student version of Metamorphic Rocks Table

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