03_igneous_rocks_09_post

03_igneous_rocks_09_post - Lecture 3: Igneous rocks

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cture 5: 1 Lecture 3: Igneous rocks Kilauea Volcano, Hawaii.  Photo: USGS
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cture 5: 2 Why is this topic important? Igneous rocks  reveal hints  about the  composition and  pressure- temperature  conditions of  rocks that were  melted to form  igneous rock.
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cture 5: 3 Why is this topic important? Igneous rocks are  associated with  volcanism, which forms  a significant geologic  hazard 1991 Eruption of Mt. Unzen, Japan Photo: AP
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cture 5: 4   Magma : molten rock  derived from melting  of the mantle or crust Magma -- generally less dense than surrounding rocks Rises to surface Fig. 6.2
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cture 5: 5 Basics: Intrusion and extrusion   Lava : magma that  has reached Earth’s  surface   Pluton  (igneous  intrusion) : magma  that has intruded  other rocks Fig. 6.2
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cture 5: 6 Plutons Fig. 6.12 At time 1: Magma (red) intrudes  older intrusions (gray) and  sedimentary layers (brown); some  magma reaches Earth’s surface to  form volcanoes and lava flows At time 2: Following cooling and  erosion
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cture 5: 7 Basics: Types of plutons   Dike : tabular pluton that cuts across layering in intruded rock Fig. 6.10
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cture 5: 8 Basics: Types of plutons   Sill : tabular pluton that is parallel to layering in intruded rock Fig. 6.10
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cture 5: 9 Plutons Fig. 6.12 Batholith Batholith : the largest  pluton
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cture 5: 10 Basics: Types of plutons     Batholith : the largest of plutons Sierra Nevada batholith, Yosemite National Park,  California.  Photo: R.W. Schlische Batholith Batholith
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cture 5: 11 Basics: Texture Thin sections Phaneritic : coarse-grained Aphinitic : fine-grained Photos: R. Siever Texture : size and arrangement of mineral grains in a rock
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cture 5: 12 Basics: Texture Porphyritic Porphyritic : large crystals in fine-grained matrix : large crystals in fine-grained matrix Photomicrograph  (50x) of porphyritic  andesite with  phenocrysts of  hornblende (brown)  and plagioclase  (white). Photo: P. L. Kresan
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cture 5: 13 Basics: Texture Pumice Ash Obsidian Glassy : no crystalline grains Pyroclastic : composed of lava fragments Photos: C. Clark
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cture 5: 14 Basics: Composition “Dark”-colored “Dark”-colored “Light”-colored “Light”-colored Mafic : “dark”-colored  igneous rocks, rich in  minerals containing  magnesium and iron  (Fe). Felsic : “light”-colored  igneous rocks, rich in  quartz and feldspar  minerals Photo: C. Clark See Fig. 6.17
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cture 5: 15 Review Questions 3-1.  A. True / B. False:  Magma is the term for molten rock below the Earth's surface. 3-2. 
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03_igneous_rocks_09_post - Lecture 3: Igneous rocks

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