rocks - quia · porphyritic a mixture of large and small crystals. the magma started to cool (freq....
TRANSCRIPT
RocksSaturday, May 29, 2010
Outline
• Igneous Rocks - Emplacement Style, Textures, Composition
• Sedimentary Rocks - three types
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Magmawell…
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Extrusive
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Intrusive
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What do you think?... Shovel Point, MN
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Textures
Coarse-grained Fine-grained Glassy Porphyritic Vesicular
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Formation from Magma
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Formation from Magma
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Bowen’s Reaction Series
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Textures (cont.)Term Description What it means?...
Coarse-grained
Mostly made up of large mineral crystals.
Fine-grained
Made up of small crystals that cannot be seen by the unaided eye.
Porphyritic A mixture of large and small crystals.
Glassy Really small crystals with a rock that looks glassy.
Vesicular Rocks with bubble holes (vesicles) trapped in the rock.
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Texture???
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Texture???
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Texture???
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Textures (cont.)Term Description What it means?...
Coarse-grained
Mostly made up of large mineral crystals.
The magma cooled slowly.
Fine-grained
Made up of small crystals that cannot be seen by the unaided eye.
The magma cooled faster than above but slower than glassy. Freq. erupted.
Porphyritic A mixture of large and small crystals.
The magma started to cool (freq. in magma chamber) and then was erupted.
Glassy Really small crystals with a rock that looks glassy.
The magma cooled quickest. Highly viscous magma.
Vesicular Rocks with bubble holes (vesicles) trapped in the rock.
Rapidly cooling magma traps bubble holes.
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Textures
Coarse-grained Fine-grained Glassy Porphyritic Vesicular
PumicePorphyritic GraniteObsidianRhyolite, BasaltGabbro, Granite
Done???
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Coarse-grained
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Fine-grained
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Glassy
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Porphyritic
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Vesicular
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Composition
Igneous Rocks
Felsic (high Silica) Intermediate (low silica) Mafic (really low silica)
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What’s the difference???
Igneous Rocks
Felsic (high Silica) Intermediate (low silica) Mafic (really low silica)
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Why do we care???... Pretty
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Geothermal Energy
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Hazardous…
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Why do we care?... The present is the key to the past… And more…
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Sedimentary Rocks
• Depositional Environments• Features• There are three types:
– clastic - has fragments (grain size), can have evidence of moving water.
– chemical - precipitation of dissolved minerals.– organic - accumulated debris of living things.
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Depositional Environments
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Features in Sedimentary Rocks
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Clastic Seds - What is grain size?
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Very Coarse
Coarse
Fine
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Breccia
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Coal
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Conglomerate
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Iron Ore
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Limestone
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Evaporite
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Metamorphic Rocks
• Foliated vs. Non-foliated
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Foliation
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Slate
Phyllite
Schist
Gneiss
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Non-foliated
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Non-foliated
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