Rocks%20and%20the%20Rock%20Cycle

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Rocks and the Rock Cycle
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El Capitan in Yosemite How did this form?

• 
  www.nps.gov

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Classifying Rocks

• Igneous
• Sedimentary
• Metamorphic
• Based on how they formed

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Igneous Rock

• Rock that forms from magma
• Magma mix of molten rock, gases and water vapor
  that forms underground
• Magma flows from volcanoes as lava and then
  hardens

http//pubs.usgs.gov/ publications/tex
t/Krafla. html
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Two types of igneous rock

• Intrusive rock - forms underground from hardened
  magma
• Cool slowly create crystals

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• Granite cools slowly so crystals form

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• Extrusive Rock forms at Earths surface
• Cools quickly so no large crystals

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• Obsidian cools very rapidly so atoms cant make
  crystals

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Sedimentary Rock

• Rock that forms over time as sediment is squeezed
  and cemented together
• Pressure causes the layers to compress

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Three types of Sedimentary rock

• Clastic
• Chemical
• Organic

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Clastic Rock

• Sedimentary rocks that form from broken fragments
  of other rocks
• Ex. conglomerates

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Chemical Rock

• Formed when minerals precipitate out of solution
• Ex. Rock salt

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Organic Rock

• Form due to organic processes
• Ex. Calcium carbonate from marine shells
• limestone

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Metamorphic rock

• Rock that has been changed by temperature,
  pressure or reactions with hot water
• Made from all three types of rock

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• Ex. Gneiss

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Rock Cycle

• Series of processes in which rocks continuously
  change from one type to another
• Caused by forces within the Earth and at the
  surface

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