Igneous Rock 12/1/14

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Igneous Rock 12/1/14
4-2 pgs. 87-90
IN Explain, using words and pictures, how rocks
form.
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sedimentary rock
compaction, cementation
sediment
high temperature great pressure
weathering and erosion
igneous rock
metamorphic rock
cooling, crystallization
melting
magma
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(No Transcript)
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How are igneous rock formed?

• Rocks are heated enough to melt its minerals into
  magma.
• Magma cools into various types of igneous rock
  depending on the composition of the magma and the
  amount of time it takes the magma to cool and
  solidify.

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How are igneous rock classified?

• Like all other rock, igneous rock is classified
  according to its composition and texture.

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How does magma form?

• Temperature
• An increase in temperature deep within the
  Earths crust can cause the minerals in a rock to
  melt.
• Different minerals melt at different
  temperatures, from about 700 to 1250 degrees
  Celsius.

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How does magma form?

• Pressure
• The high pressure deep within the earth forces
  minerals to stay in the solid state, so when hot
  rocks rise to shallow depths the pressure is
  released and they melt.

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How does magma form?

• Composition
• Sometimes fluids like water and carbon dioxide
  enter a rock that is close to its melting point.
• Remember, water melts above 0 degrees Celsius and
  carbon dioxide melts above -78 degrees Celsius.

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Composition

• Felsic - light-colored (Light as a Feather)
• Less denselight
• Rich in elements such as silicon, aluminum,
  sodium and potassium.
• Granite, Obsidian,
• Pumice

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Composition

• Mafic - dark-colored (dark as Midnight)
• More denseheavy
• Rich in elements such as iron, magnesium, and
  calcium
• Basalt

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Texture

• Intrusive Igneous Rock
• When magma cools beneath the Earths surface.
• Coarse-grained texture
• Cools slowly

Granite Basalt (because the pressure of the
ocean makes the crystals small)
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Big amount of timeBig crystalsCoarse Grain
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Texture

• Extrusive Igneous Rock
• When lava cools on the Earths surface.
• Fine-grained texture
• Cools quickly

Small amount of time small crystals
Pumice Obsidian
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Granite

• Igneous plutonic rock formed when magma cools
  slowly.
• Remember its made up of mica, feldspar, and
  quartz...all silicates.
• Felsic
• Intrusive
• Coarse-grained

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Basalt

• Igneous volcanic rock with small crystals made
  when lava cools.
• Mafic
• Intrusive/Extrusive
• Fine-grained

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Obsidian

• Igneous rock formed from volcanoes that has sharp
  edges and looks like glass.
• Felsic
• Extrusive
• Fine-grained

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Pumice

• Igneous rock with holes and can float on water.
• Felsic
• Extrusive
• Coarse-grained

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• OUT What are some features of igneous rocks?