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Geos 432-4 Volcanic Landforms

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Geos 432-4 Volcanic Landforms GEOS 432-4; Volcanic processes and landforms Plate Tectonics and Volcanism Mantle hot spots Oceanic Basaltic Continental Rhyolitic, andesitic, or basaltic Plate tectonics and Volcanism Plate margins Divergent-basaltic Subduction of oceanic plate-andesite 1 Large scale landforms Submarine volcanoes Large scale landforms Basalt plateaus Volcanic Products Gas Lava Tephra 2 Gas Vents Hot springs, geysers, fumaroles, solfataras Hot springs Solfatara, Iceland Geyser, ―Strokkur‖ at Geysir, Iceland 3 1 2 3 4 Mud volcano http://ngm.nationalgeographic.com/ngm/20 08-01/volcano-culture/drowning-in- mud.html 4 Lake Nyos case history http://perso.wanadoo.fr/mhalb/nyos/index.htm Lava Composition Silica content: 35% (basalt) – 75% (rhyolite, obsidian) Viscosity Related to composition-higher silica—more viscous Temp and volatile content also important Volatiles decrease viscosity but degas at surface Basalt 1100-1200 degrees C Lava flows Vesicles AA Aaflow, lava Iceland Pahoehoe lava Aa lava flow 5 Rhylolite/obsidian flow Obsidian Columnar jointing 6 Pillow lavas Tephra Ash—sand size & smaller Lapilli—gravel Blocks (Cold) Bombs (warm) Pumice, 1875 eruption of Askja, Iceland 1875 Snow exposed 7 Pyroclastic eruptions Heimaey, Iceland, 1973 2010 Eruption: Eyjafyallajökull http://www.youtube.com/watch?v=f1ztg0wUqKY Pyroclastic flow or surge High temperature, very fast, very destructive 8 Mt. Pelee, 1902 Town of St. Pierre, Carribean Island of Martinique 30,000 killed Mt. St. Helens, 1980 Lateral Blast Debris flows, Mt. St. Helens 9 Mt St. Helens Lahars Orting, Washington Mt. Rainier Mt. Shasta 10 Armero, Nevado del Ruiz, 1985 23,000 people killed Volcanic landforms ShieldShield volcano volcano Shield volcano L Lava flow Exogenous dome a v a Scoria cone ScoriaScoria cone cone Scoria Scoria cone cone Tuff ring Endogenous dome Ruptured ED Composite (strato) volcano Explosion caldera Maars with tephra Maar with rampart Collapse caldera Gas maar Explosion crater 11 Lava flows—fissure or central vent Young lava flow, Iceland Fissures, Iceland Iceland Lava Cascade, Iceland Fissure, Craters of the Moon 12 Basalt flow Craters of the Moon Miocene basalt flows from fissures- Columbia River Plateau Exogenous domes Spatter cone-Iceland Shield Volcano-Iceland Mauna Loa, as seen from Kilauea Mauna Loa from Kilauea 13 Pyroclastic cones, rings Tuff ring, northern Iceland Scoria cone Tuff cone 14 Tuff Ring, Iceland Lake Myvatn, Iceland 15 Endogenous domes Mt. St. Helens Composite (strato) volcanoes 16 Mt. Fuji Craters, calderas Maar, New Mexico Crater Lake 17 Halemaumau pit crater Summit caldera, Askja Volcano, Iceland Santorini, Greece 18 Miscellaneous IcelandicIcelandic Table Table Mountain Mountain -Tuya Tuya, Iceland Miscellaneous con’t Lava tube Tumuli Volcanic neck Tree mold 19 .
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