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30 Cards in this Set
- Front
- Back
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How are Igneous Rocks Classified?
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Texture Composition |
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Phaneritic Texture
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Minerals large enough to see with unaided eye Magma cooled slowly |
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Intrusive/Plutonic Igneous Rocks
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Igneous rocks formed underneath the surface, rose from the mantle because it was less dense than the surrounding rock
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Aphanitic Texture
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Mineral crystals too small to see with naked eye Indicates rapid cooling |
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Extrusive/Volcanic Igneous Rocks
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Most likely aphanitic texture, lava reached the surface and cooled rapidly
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Porphyritic Texture
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Large crystals embedded in small ones Magma initially cools slowly, then escapes to the surface and cools rapidly |
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Glassy
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Lava solidifies too quickly and is quenched Unordered ions remain frozen before solidified into crystals |
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Vesicular
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Magma solidifies with bubbles of gas trying to escape trapped in it Produces holes in the rock |
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Frothy
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Extreme vesicular texture - can float on water
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Pyroclastic
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Produced from violent eruptions Made of large pieces of rocks or blobs of molten material with bits of rock in it |
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Minerals of Igneous Rocks
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Ferromagnesian silicates, feldspars, quartz
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Ferromagnesian Silicates
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Fe and Mg ions ionically bonded with silica units - tend to be DARK COLOURED
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Feldspars
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Silica framework rich with light ions (K, Na, Ca), tend to be LIGHT COLOURED
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Quartz
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Pure silica
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Crystallization Sequence Bowen's Reaction Series |
Ferromagnesian silicates crystallize discontinuously, dark-coloured minerals formed at higher temps Feldspars crystallize continuously Potassium Feldspar, Mica, and Quartz crystallized last in lowest temperature |
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Types of Igneous Rocks Composition
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Mafic, Felsic, Intermediate
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Mafic
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High concentration of dark-coloured (ferromagnesian) minerals ("ma" = magnesium" "fi" = iron)
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Felsic
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High concentration of light-coloured minerals ("fe" = feldspar "si" = silica)
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Intermediate Rocks
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Both mafic and felsic
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Mafic, Phaneritic
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Gabbro
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Mafic, Aphanitic
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Basalt
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Phaneritic, Intermediate
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Diorite
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Aphanitic, Intermediate
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Andesite
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Felsic, Phaneritic
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Granite
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Felsic, Aphanitic
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Rhyolite
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Why is it difficult to melt rock?
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Temperature increases with depth = more liquid Pressure increases with depth = more solid |
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Methods to melt igneous rocks
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Decompression melting, hydration melting
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Decompression Melting
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Magma generated in places where plates are moving apart, releases pressure and allows melting Extrusive - basalt Intrusive - gabbro |
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Hydration Melting
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Steam from water helps speed things along Extrusive - felsic/rhyolite, intrusive -> diorite/granite Can also increase silica content |
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Can fossils be found in igneous Rock? |
Generally, no Ash can preserve things |
