Chapter 11 The Rock Cycle

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Chapter 11The Rock Cycle

• Section 11-1
• Igneous Rocks

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I. How do igneous rocks form?

• Rocks are a mixture of one or more minerals
• Can be a mixture of mineraloids, glass, organic
  particles
• Often several different minerals are mixed
  together
• Gives rock color and texture
• Sometimes mineral pieces are large enough to see
  without a microscope

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B. How do minerals combine to make rocks?

• Magma is trapped below the surface
• Magma/lava cools and becomes hard
• Crystals and minerals form
• Crystals grow together and form solid igneous
  rock
• Igneous rock rock formed as molten material
  cools

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C. Intrusive Igneous Rocks

• Formed beneath Earths surface through the
  process of crystallization.
• Can be found on Earths surface when the rock and
  soil that covered them is eroded or when pushed
  out by tension or compression forces.

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D. Extrusive Igneous Rocks

• Lava cooled on the Earths surface through the
  process of consolidation.
• Exposed to air and moisture
• Minerals form quickly and are smaller than
  intrusive igneous rocks
• Most of these minerals can only be seen through a
  microscope
• Most common extrusive igneous rock is basalt
• Ex. Hawaiian Islands black sands, formation of
  islands

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• Some Examples of Igneous Rocks
• Granite
• Scoria
• Pumice
• Obsidian

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II. Classifying Igneous Rocks

• Igneous rocks are classified based on the size of
  their crystals also known as their texture
• Coarse-grained rocks rocks with large visible
  crystals
• Fine-grained rocks rocks with tiny crystals
• Examples
• Also classified based on color
• Light-colored light colored minerals (quartz,
  feldspars)
• Dark-colored dark colored minerals (pyroxenes,
  amphiboles)

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• Igneous rocks are the most abundant type of rock
• Why study rocks?
• Hypothesize how Earth formed
• Determine how mountains form (Ex. Rockies)
• Determine how rock layers form and erode away
  (Ex. Grand Canyon)