Types of Volcanoes

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  • FISSURE
    • VOLCANO TYPES
      • SHIELD
        • C PM or HSPs
        • basaltic rock
          • form gently sloping cones, less viscous lava
        • gentle & unpredictable
        • Mauna Loa, Hawaii
        • basaltic
      • COMPOSITE
        • most common found on land
        • D PM
        • layers of ash - initial explosive phases & subsequent lava layers main eruption
        • rhyolitic lava
          • thick, viscous
          • magma cools in main vent
            • plugs and traps
          • gas released through secondary vent
            • sudden and violent release
        • Mt Etna & Vesuvius
        • explosive & unpredictable
      • ACID / DOME
        • continental crust
        • steep sided
          • formed from viscous lava
            • can't travel far, convex volcanoes
        • lava may solidify in vent
          • revealed later by erosion
        • Puy de Domes, France
        • explosive & unpredictable
        • Rhyolitic
      • CALDERA
        • D PM
        • form from built up gases
          • blocked vent - catastrophic eruption, destroy summit
            • enormous crater
              • sometimes fills with water
        • eruptions = explosive and unpredictable
        • Krakatoa, Indonesia
        • andesitic
          • lower temp
          • more silica, viscous, doesn't travel far
          • dissolved gas
            • likely to explode
              • high eruptions spread gases
                • may cause collapse of column
    • elongated crack in crust, lava spill over large area
      • 2010, Eyjafjallajokull
    • C PM
    • typically @ spreading ridges (MA)
    • basaltic lava
    • gentle & persistent
    • basaltic
      • hot
      • low viscosity
      • easy release of gases
        • non-violent eruptions
      • runny lava
        • low cones = low gas plumes
      • lava spreads far, cools quickly
        • cones = low and wide based

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