Shapes of Volcano

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  • Shapes of Volcano
    • Fissure Eruptions
      • Occur when an elongated crack in the crust allows lava to spill out over a large area
      • Location: rifts/early constructive (divergent) margins
      • Example: Iceland
        • Eurasian and North American plates are pulled apart
      • Lava: Basaltic
      • Eruptions: gentle, persistent
    • Shield Volcanoes
      • Lava: Basaltic
      • Locations: Hot spots and where oceanic crust meets oceanic crust
      • Eruptions: gentle, predictable
      • Shape: gently sloping cones
      • Example: Mauna Loa in Hawaii
        • Stands 4,170m above sea level with a volume of 40,000km2
      • Created by layers of less viscous lava
    • Composite Volcanoes
      • Lava: Andesitic
      • Location: Destructive (convergent) margins
      • Shape: Cone shape
      • Most common type found on land
      • Created by layers of ash from initial explosive phases of eruptions and subsequent layers of lava from main eruption phases
      • Eruptions: Explosive, unpredictable
      • Example: Mount Etna
    • Acid or Dome Volcanoes
      • Shape: Steep-sided volcanoes . Convex cone-shaped
      • Lava: Rhyolitic
      • Formed from very viscous lava - as the lava cannot flow far, it builds up
      • Location: Continental crust
      • Eruptions: Explosive, unpredictable
      • Examples: Puy de Domes, France
    • Calderas
      • Lava: Andesitic
      • Location: Destructive margins
      • Eruptions: Very explosive, unpredictable
      • Form when gases that have built up beneath a blocked volcanic vent result in a catastrophic eruption that destroys the volcanic summit
        • Leaves an enormous crater where later eruptions may form smaller cones
      • Example: Crater Lake in the US, The caldera has filled with water
      • Example: Krakatoa in Indonesia


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