Geol 1040 1st Edition Lecture 11Outline of Last Lecture XXIII. Igneous Rocksa. What is magmab. What causes magma to be pushed outc. Igneous rocks are formed when magma coolsXXIV. Characteristics of magmaa. Extrusiveb. Intrusive/ PlutonicXXV. Classification of igneous rocksa. TexturesAmount of silicaXXVI. Types of Igneous texturesa. Aphaniticb. Phaneriticc. Porphyriticd. Pegmatice. GlassyOutline of Current Lecture XXVII. Igneous Compositiona. Dark Mafic Mineralsb. Light Felsic mineralsc. ExamplesXXVIII. Origin of Magmaa. Generating magma from solid rockb. 3 Mechanisms rock melt byXXIX. Role of Heata. Geothermal Gradientb. Conductionc. Radiant Heat transferd. Convectione. Transferring thermal energy via plate tectonicsXXX. Role of pressurea. Higher pressure b. Low Pressure c. Decompression These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.XXXI. Role of heat and mantle convection away from plate boundariesa. Hot spotXXXII. Role of Volatilesa. Flux meltingb. Water acts as a volatile and lowers melting temperaturec. Important for subduction zones where oceanic lithosphere descends into the mantleXXXIII. Magma and Plate tectonicsa. Decrease in Pressureb. Increase Temperaturec. VolatilesCurrent LectureXXVII. Igneous Compositiona. Dark Mafic Mineralsi. Olivine1. Some calcium rich feldspars are not dark but are maficb. Light Felsic mineralsii. Quartziii. Muscoviteiv. Feldsparc. Examplesv. Granite = Felsic1.vi. Diorite (salt and pepper look) = Felsic & Mafic1.vii. Basalt= Mafic (extrusive)1.viii.XXVIII. Origin of Magmac. Generating magma from solid rocki. Partial melting of solid rock in crust and upper mantleii. Occurs mainly at the lithosphere and asthenosphere boarderd. 3 Mechanisms rock melt byi. Increase in temperatureii. Decrease in Pressureiii. Addition of volatiles 1. Adding things like water, which bring down the meltingpointiv. *Sometimes the same effects happen on the surface.2. I.e. meteor impact, and lightning strike. However thesedo not produce actual magma but can create igneoustype rocks. XXIX. Role of Heatf. Geothermal Gradienti. Temperature is higher the lower into the Earth you gog. Conductioni. Transfers heat by direct contacth. Radiant Heat transferi. Thermal radiation heats nearby objectsi. Convectioni. Materials flow around a circular path.ii. As material heats up it rises because it becomes less dense.3. It then cools and settles downiii. The process is in a lava lampj. Transferring thermal energy via plate tectonicsi.ii. Convection happens along Mid Ocean Ridgesiii. Conduction happens along the crust and mantleiv. Radiation of heat happens at volcanoes.XXX. Role of pressured. Higher pressure i. increase the melting temperature of a rocke. Low Pressure i. decreases the melting temperaturef. Decompression i. Melting that occurs from lowering pressure4. Found in ridgesXXXI. Role of heat and mantle convection away from plate boundariesb. Hot spoti. Mantle heat convectsii. Is not molten until it reaches the lower pressure of the lithosphereXXXII. Role of Volatilesd. Flux meltinge. Water acts as a volatile and lowers melting temperaturef. Important for subduction zones where oceanic lithosphere descends into the mantleRadiationXXXIII. Magma and Plate tectonicsd. Decrease in Pressurei. Mid ocean ridgeii. Continental riftsiii. Continental collisione. Increase Temperaturei. Hot Spotsf. Volatilesi. Subduction
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