GEOL 101:Volcanoes and Volcanism: Lecture 20
GEOL 101:Volcanoes and Volcanism: Lecture 20 101-017
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This 3 page Class Notes was uploaded by Natalee Stanton on Monday February 29, 2016. The Class Notes belongs to 101-017 at University of South Carolina taught by in Winter 2016. Since its upload, it has received 35 views. For similar materials see Geology 101-017 in Geology at University of South Carolina.
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Date Created: 02/29/16
GEOL 101: Volcanoes and Volcanism Volcanism – process by which magma (usually form the mntle) rises through the rust, emerges onto the surface as lave, and cools into hard volcanic rock forming volcano I. Types of lavas Basaltic lavas – low viscosity mafic lavas, typically erupted at 1000 C cool to form basalt Rhyolitic lavas – high viscosity felsic lavas, typically erupted at 800 C cool to form rhyolite Andesitic lavas – intermediate in composition and viscosity between mafic and felsic magmas cool to form andesite II. Types of basalts Flood basalts – thick, widespread accumulation of basalt, typically fed by fissures Pahoehoe – a very low viscosity basaltic lava characterized by a ropy texture o Found in Hawaii o Rope texture Aa. A relatively low viscosity basaltic lava characterized by a jagged, blocky texture o Found in Hawaii Pillow basalts – a basaltic lava extruded beneath the water, with a glassy texture o Quickly cools in cold water Vesicular Basalt – trapped gases form bubbles (vesicles) Like a can of soda that is shaken up Pumas Pyroclastic deposits Fragmentary volcanic rocks ejected high into the air during violent eruptions o Volcanic ash o Volcanic tuffs o Volcanic breccias Partially cooled magma o Volcanic bombs Large quantities of hot magma coming out of the volcano Pyroclastic flows Density flow of hot (800 C) Poisonous gas and pyroclastic material 200 km/hr o Can’t out run them Fatal Phreatic explosion Magma eruption in water Fissure eruptions Eruption originating along an elongate fissure rather than a central vent These happen in Iceland III. Lahars (volcanic mudflows) Formed by the sudden mixing of large volumes of pyroclasts with water o Heavy rain o Draining of crater lake o Melting glaciers Move 100+ km/hr Cover large areas Hot Geosystem interactions Volcanism and Hydrosphere – water in the ground o Fumaroles and geysers Volcanism and the atmosphere o Aerosols and ash IV. Hydrothermal activity The circulation of water through hot volcanic rocks and magma o Forms fumaroles – volcanic vents emitting gases, some charged with dissolved minerals o Forms geysers – heated hydrothermal waters under pressure, that intermittently erupt o Provides the source for Geothermal Energy Sample Exam Questions What is the name for a basaltic lava flow that has a ropy, folded surface? a. Aa b. Breccia c. Pahoehoe d. Tuff Organisms that gain energy form feeding directly or indirectly on producers are referred to as___. a. Autotrophs b. Chemptrophs c. Phototrophs d. Heterotrophs What is molten rock beneath the Earth’s surface called? a. Granite b. Magma c. Lithosphere d. Lave At what boundary within the Earth do we believe that mantle plumes (hot spots) originate? a. Crust mantle boundary b. Lithosphere – asthenosphere boundary c. Mantle – outer core boundary d. Outer core inner core boundary
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