VOLCANISM Mount St Helens 1980 eruption Where are Slides: 50 Download presentation VOLCANISM Mount St. Helens, 1980 eruption Where are volcanoes located? Volcanoes are located over divergent plate boundaries (mid-oceanic ridges) Laki fissure, Iceland Volcanoes are located over convergent plate boundaries (subduction zones) Mount Rainier, Tacoma, Washington Volcanoes are located over Hot spots What are the products of volcanism? Welded tuff (ash & flow deposits) Vesicular Basalt Pyroclastic eruption at Arenal Volcano, Costa Rica Volcanic Bombs Pyroclastic flow at Mount Unzen Volcanic Breccia WHY DO DIFFERENT VOLCANOES HAVE DIFFERENT SHAPES? Gentle-slopes (Shield Volcano) Gentle-slopes (Shield Volcano) Non-explosive eruptions Basaltic flows Low-viscosity Lava Low Si. O 2 content Mafic composition steep-slopes (Cinder-cone Volcano) steep-slopes (Cinder-cone Volcano) Pyroclastic material High Si. O 2 content More Felsic composition steep-slopes (Composite Volcano) steep-slopes (Composite Volcano) Alternating layers of Basaltic flows and pyroclastic material Mafic-felsic composition Volcanic domes Volcanic domes Felsic lava Very high viscosity Lava accumulates over the vent Evolution of Crater Lake Caldera Mount St. Helens (Before eruption) Mount St. Helens (During eruption) Mount St. Helens (After eruption) Mount St. Helens (Before eruption) Hot Spots and Plate movement Volcanic Hazards Pyroclastic Flows are the most dangerous Before and after mt st helens eruptionMount st helens plates involvedMikael fermMount etna 1669 eruption factsMount unzen eruption 1792 factsMt rainier eruption simulationVesuvius locationNwa 11119Intraplate volcanismNajničivejšie tsunamiHilton st helensElastic rebound theory describes:Saint helens tsunamiSt helens tsunamiSlope angle of mt st helensEruption 1991Stratovolcano plate boundaryObat creeping eruptionVolcano type of eruptionConvergent platesEruptio difficilisPlate tectonicsTypes of volcanoesProcess of volcanic eruptionWhat are the steps of secondary successionVolcano type of eruptionFactor affecting volcanic eruptionLake nyos disaster photosMazama volcanoCherniss 1980Teori lawrence green1980Pae programa de ajuste estructural costa ricaGinebra 1980Babka v fct1980-1950Piaget equilibriumJean piaget (1896-1980)Akta badan berkanun 1980Toshiba 1980 flashOlimpiadi mosca 19801980-1963Bem 1980Forest conservation act 1980Daniel tanner 1980Mini comtesse peugeot 198050-luvun muoti naiset14 sierpnia 1980Department of land surveying and geo-informaticsNota de 10000 escudosPiaget 1896