Chapter 3 section 2 igneous rocks
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Chapter 3 Section 2 Igneous Rocks. From the core of the continents to nearly all of the oceanic crust—igneous is everywhere!. IGNEOUS ROCKS. magma lava. “fire” rocks. cooling. andesite. pumice. Formed from cooled/hardened _________ or ______

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Chapter 3 Section 2 Igneous Rocks

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Chapter 3 section 2 igneous rocks

Chapter 3 Section 2 Igneous Rocks

From the core of the continents to

nearly all of the oceanic crust—igneous is everywhere!


Igneous rocks

IGNEOUS ROCKS

magma lava

“fire” rocks

cooling

andesite

pumice

Formed from cooled/hardened _________ or ______

Are called _______________ [ignis Latinfire]

The rate of __________ determines the size of the mineral’s crystals.

basalt


Chapter 3 section 2 igneous rocks

INtrusive: below groundcools slower many many &large crystals

Ex: granite, gabbro


Intrusive igneous

Intrusive Igneous

  • Visible due to erosion & weathering

  • Magma= mainly silicon & oxygen

    • Gases: water vapor (gases trapped)

  • Magma less dense than surrounding rock moves towards surface & cools

    • Elements combine minerals form & ‘grow’ crystals!

      • Example:

        • Granite

        • Cumberlandite


Intrusive igneous cumberlandite

Intrusive Igneous: Cumberlandite

  • Only found in Cumberland, RI (official state rock)

    • 4-acre lot in Blackstone Valley (Iron Mine Hill) & trace amts. Narr. Bay

  • Dense & prone to rust (iron  magnetic); titanium, transitions to peridotite (intr. coarse ign.)

  • Formed 1.5 bya  volcanic activity

  • Valuable  cannon and farm tools 18th/19th cent.


Chapter 3 section 2 igneous rocks

Obsidian

EXtrusive: above groundcools quicker f e w &small crystals

Air bubbles are sometimes trapped (pumice, scoria)

Basalt


Extrusive igneous

Extrusive Igneous

Basalt

  • Magma = below ground// Lava= above ground

    • Lava most gases escaped

  • Lava hardens extrusive igneous rock

    • Extruded onto surface

    • Example: Rhyolite, Basalt


Classifying igneous rocks

Classifying Igneous Rocks

  • Classification based on two major characteristics:

    • Texture: appearance based on size, shape & arrangement of crystals

    • Composition: proportions of light and dark minerals


Classification texture

Classification: Texture

  • Coarse-grained: slow cooling large crystals

    • Allows charged atoms (ions) to move large distances within magma & link together (crystallize)

  • Fine-grained: rapidcooling  small crystals

    • Ions lose motion and quickly combine; all compete for available ions

  • Glassy: lava on surface little time for ions to

    crystallize randomly distributed 

    glassy appearance (tiny crystals)

  • Porphyritic: different-sized minerals experience

    different rates of cooling

    • Large crystals (phenocrysts) may be surrounded by

      fine grained minerals

    • Minerals don’t crystallize @ same rate (location and

      melting point.)


  • Classification composition

    Classification: Composition

    • Granitic: light-colored silicates (quartz & feldspar)

      • 70 % silica

      • 10 % dark silicate minerals (i.e. biotite mica, amphibole)

      • Major component of continental crust

      • Ex: rhyolite = extrusive granitic rock

    • Basaltic: contain many dark silicate materials (plagioclase feldspar)

      • Rich in magnesium and iron

        • Iron  darker and denser than granitic rocks

      • Ex: gabbro = intrusive basaltic rock

    • Andesitic: composition between granitic and basaltic

      • Volcanic rock = andesite:

        • At least 25 % dark silicates (amphibole, pyroxene, biotitemica)

        • Dominant mineral plagioclase feldspar :type of feldspar dark w/ridges (striations)

    • Ultramafic: composed almost entirely of dark silicate minerals

      • Rare @ Earth’s surface

        • Ex: peridotite—upper mantle composition


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