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About Rocks
   
Devil's Tower, Wyoming by jimbowen0306 on Flickr

Igneous rocks are called fire rocks and are formed either underground or above ground.

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obsidian by kevinzim on Flickr

This is obsidian - an igneous rock.

 

Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks.


 

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Hot Lava Christmas by jurvetson on Flickr

Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava.

 

 

Igneous rocks are formed as the lava cools above ground.

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Metamorphic by subarcticmike on Flickr

Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks.

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Quartzite vein, in Pelite/Psammite, Dalradian metamorphic rock, Creigh Hill, 16/02/2008 by Shandchem on Flickr

How do sedimentary and igneous rocks change? 
  • The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change.
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serpentine texture by kevinzim on Flickr

If you examine metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.
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sandstone by kevinzim on Flickr

This is sandstone - a sedimentary rock.


For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away
by wind and water.

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Rote Steine, grĂ¼ne Pflanzen (Bryce Canyon National Park) by Sebastian Fuss on Flickr

These little bits of earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each.

 

These layers are pressed down more and more through time, until the bottom layers slowly turn into rock called sedimentary rock.

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Geode by Fermion on Flickr

This is Geode - a sedimentary rock.

 

 

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