Geol 303 Natural Disasters Chapter 7 Notes

Geol 303 Natural Disasters Chapter 7 Notes - Geology 303...

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Geology 303 Natural Disasters Chapter 7: Volcanic Eruptions: Plate Tectonics and Magmas Vesuvius, Italy: Volcanic eruption buried Pompeii in a flow of hot gas and volcanic ash 500 C/ 940 F Plate-tectonic Setting of Volcanoes 90% of volcanoes are associated with the edges of tectonic plates Subduction zones cause volcanic mountains on edges of continents Andesitic / rhyolitcs; explosive Spreading centers release far more magma than subduction zones Basaltic magma; peaceful Chemical and Mineral Composition of Magmas 8 elements make up 98% of Earth’s crust O (45), Si (27), Al (8), Iron, Calcium, Magnesium, Sodium, K Continental Crust SiO2 (60%); Al2O3 (15%) Oceanic Crust SiO2 (49%); Al2O3 (17%); CaO (12%) Elements bond to make minerals The process of mineral formation in a cooling is called crystallization Minerals aggregate to form rocks Igneous Rock Types SiO2 < 55% Gabbro/Basalt Viscous, High temp ex. Olivine SiO2 = 55-65% Diorite/Andesite SiO2 > 65% Granite/Rhyolite Lower temp ex. Quartz Plutonic rocks are formed when magma cools and solidifies BELOW the surface Volcanic rocks are formed if the magma reaches the surface Viscosity, Temperature, and Water Content of Magmas
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This note was uploaded on 07/29/2009 for the course GEOL 303 taught by Professor Camp during the Spring '07 term at San Diego State.

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Geol 303 Natural Disasters Chapter 7 Notes - Geology 303...

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