Causes and effects of Montserrat volcanic eruption

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  • Created by: Lina
  • Created on: 12-04-14 16:49
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  • Montserrat Eruption
    • Effects
      • Some parts of the island suffered blackout conditions- the sun was obstructed by the ash cloud
      • The ash cooled-> fell back on to some parts of the island
        • Ash deposits- 2-3 mm thick
          • A total of 4 km2 was covered by deposits
      • The eruption of the volcano shouldn't have had a major impact on people
        • The affected areas were in the Exclusion Zone set up after an eruption in 1995
          • 25 June, 1997- authorised people were in the zone to carry out essential tasks+ monitor the volcanic activity.
            • An eruption looked likely-> the workers evacuated safely by responsing to the emergency sirens
              • Unauthorised people in the Exclusion Zone were too far away to hear the sirens
                • Thought they would receive audible warning from the volcano as it was going to erupt-> didn't happen-> were caught unawares
      • 7 people killed by the surge in Streatham+ Windy Hill area
      • Villages affected by deposits:
        • Dyer
        • Farrell's Yard
        • Windy Hill
        • Streatham
        • Harris
        • Farm and Trant
      • Houses in the Exclusion Zone- destroyed by the impact of rock, up to 5m in size
        • Should have been empty
          • 15 people were living there
            • Mostly farmers, who produced crops to feed evacuees
    • Causes
      • Destructive plate boundary- towards
      • The North American Plate subducted under the Carribean plate
        • Oceanic North American plate- denser than the Carribean continental plate
      • Convection currents pulled NA plate into the mantle
        • Heat+ friction-> the rock melted
          • Lighter than the surrounding rock
            • Rose through cracks towards the Earth's surface
              • Formed the volcanic island
                • Produced thick sticky lava
                  • Andesite
                  • The lava builded up at the top of the volcano in a dome
                    • Too heavy-> collapsed
                      • A huge ash cloud formed
                        • Rose rapidly
                          • A height of 10km
                          • Strong winds blew the clouds of ash westwards over the island
                      • Hot rocks, ash+ gas ejected from the volcano
                        • Pyroclastic flows
                          • Fast moving
                          • Destroy everything in their path
                          • Killed 19 people
                          • Spread out+ flattened treed on the ridge surrounding
                            • Farrell's Yard
                              • No vegetation left, just bare vegetable beds+ the soil was baked hard
    • 25 June, 1997
      • Chances Peak Volcano
        • Produced thick sticky lava
          • Andesite
          • The lava builded up at the top of the volcano in a dome
            • Too heavy-> collapsed
              • A huge ash cloud formed
                • Rose rapidly
                  • A height of 10km
                  • Strong winds blew the clouds of ash westwards over the island
              • Hot rocks, ash+ gas ejected from the volcano
                • Pyroclastic flows
                  • Fast moving
                  • Destroy everything in their path
                  • Killed 19 people
                  • Spread out+ flattened treed on the ridge surrounding
                    • Farrell's Yard
                      • No vegetation left, just bare vegetable beds+ the soil was baked hard

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