Exam 2 - Geology 1010-002 Instructor Flowers Exam#2 Review...

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Geology 1010-002, Instructor: Flowers Exam #2 – Review Sheet Fall 2007 (Exam 2 – October 17, 2007 - Wednesday, during the regular class period) Note: this is a review sheet – use it as a guide to help you study; it is not the exam Be sure to review the Homework Questions and Clicker Questions too. Chapter 4 – Igneous Rocks Magma- HOT liquid rock Lava- molten rock that flows above ground Intrusive- (plutonic) igneous rocks cool below the earths surface slowly having large crystals greater than 1 mm Extrusive- (Volcanic) igneous rocks cool on earths surface more rapidly having a finely cristilne texture Plutonic- intrusive Volcanic- extrusive Granite- large crystals, cools beneath slowly Diorite- Intrusive (coarse grained)/ intermediate, coarse grained igneous rock Gabbro- Intrusive (Coarse grained)/ Mafic (less silica, higher Fe, Mg, denser) igneous Rhyolite- Extrusive (fine grained)/ felsic ( high silica, low Fe, Mg, less dense) igneous Andesite- Extrusive/ intermediate igneous rock Basalt- Extrusive/ Mafic (less silica, higher Fe, Mg, denser) igneous Components of a magma- liquid, the melt Solids- primarily silicate minerals that have already crystallized from the melt Volatiles- gasses dissolved in the melt- water vapor, carbon dioxide, sulfur oxide Igneous textures: e.g., Aphanitic- igneous rock texture in which crystals are too small to distinguish individual minerals w out microscope Phaneritic- igneous rock texture in which crystals are roughly equal size and large enough to identify individual minerals
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Porphyritic – two distinct crystal sizes. Slow and rapid cooling Pegmatitie – extremely coarse-grained (greater than 5 cm) magma cools very slowly and depth Glassy- no crystals, extremely rapid cooling Pumice- light colored rock w gas bubbles or vesicles Relationship between rate of cooling, silica, gas content, and igneous texture Cooling determines the crystallization, silica determines mineral content and color / all of which determine the texture and content of that igneous rock. Ultramafic- less than 45% silica, dark, dense, Fe, Mg mantle, intrusive Mafic- about 50% silica, dark colored minerals, abundant Fe, Mg, Ca. ex. Gabbro (intrusive) Bassalt (extrusive) Intermediate- silica between mafic and felsic Ex. Dorite- intrusive Andesite- (extrusive) Felsic- high silica, light colored minerals, abundant Si, Al, Na, K Ex. Granite- intrusive Rhyolite- extrusive Bowen’s reaction series- During crystallization, the composition of the liquid portion of the magma continually changes Fractional crystallization- first- formed crystals in a cooling magma are separated from cooling magma. Crystals from cooling magma sink Differentiation- separation of melt from erlier formed crystals to form a different composition of magma Assimilation- changing a magma’s composition by incorporating surrounding host rocks Magma mixing- chambers merge mixing the two contents Partial melting- minerals have different melting points. If liquid is squeezed out after some melting has occurred, a melt with higher silica results.
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