CH' 5 Igneous Rocks

1
CH. 5 Igneous Rocks

• What are igneous rocks?
• Formed by the hardening of magma.
• What is the difference between magma lava?
• Lava is magma above ground.
• Types of Igneous Rock
• 1. Extrusive fine-grained igneous rocks that
  cool quickly on Earths surface.
• Ex. Rhyolite (pg.100)
• 2. Intrusive coarse-grained igneous rocks that
  cool slowly below the Earths surface.
• Ex. Granite (pg. 100)

2

• Composition of Magma
• Magma is classified based on the amount of silica
  it has.
• Table 5-1 (pg. 101)
• 1. Rhyolitic 70 Silica
• 2. Andesitic 60 Silica
• 3. Basaltic 50 Silica
• How does magma form?
• Heat and pressure under the Earths surface.
• Where does the heat come from?
• The decay of radioactive elements.
• The pressure increase the heat the deeper below
  the Earths surface the greater the pressure,
  thus more heat.

3

• Fractional crystallization the process by which
  different minerals form at different
  temperatures.
• Bowens reaction series the concept that magma
  cools forms minerals at predictable patterns.
• Fig 5-6 (pg. 104)

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Classifying Igneous Rocks

• Mineral Composition
• 3 Main Groups Table 5-2 (pg. 107)
• 1. Felsic light-colored, have high silica
  contents, and contain quartz and the feldspars
  orthoclase and plagioclase.
• 2. Mafic dark-colored, have lower silica
  contents, and contain lots of iron and magnesium.
  It also contains plagiocas, biotite, amphibole,
  pyroxene, and olivine.
• 3. Intermediate In between the two.

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• Porphyritic is a rock with texture with large
  crystals surround by finer-grained crystals.
• Fig. 5-13 (pg. 110)
• Pegmatites have veins of extremely large-grained
  minerals.
• Fig 5-16 (pg. 112)
• Kimberlites are rare ultramafic rocks that have
  diamonds embedded in them.
• Most diamonds come from mines in South Africa
• Fig. 5-17 (pg. 113)