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 case studyAntigentest åreMount etna 1669 eruption factsMount unzen eruption 1792 factsMount rainier eruption simulationMt vesuvius last eruptionIntraplate volcanismVolcanismSlope angle of mt st helensSaint helens tsunamiHilton st helensDefine elastic reboundSaint helens tsunamiSt helens tsunamiVolcanic ashObat creeping eruptionVolcano type of eruptionTectonic playe mapEruptio difficilisStrombolian eruptionFactors affecting magma viscosityProcess of volcanic eruptionSuccession definition biologyVolcano type of eruptionFactor affecting volcanic eruptionJillian maloneCrater lake eruptionEruption 1991Akta badan-badan berkanun (tatatertib dan surcaj) 20001980 toshiba flashOlimpiadi mosca 19801963-1980Bem 2000Daniel tanner 1980Forest conservation act50-luvun muotiBenz patent motorwagen14 sierpnia 1980Hk 1980 gridJean piaget 1896 a 1980Icdh full formNotas antigas portuguesasWipro share price in 1980Lambang bulan sabit merah1980-1896Stuart hall theory1970 1980 1990Year 1980 in wordsDonabedian 1980Harta europa politica