Montserrat Eruption

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  • Created by: Lina
  • Created on: 12-04-14 18:34

Montserrat Eruption

Causes

  • The island is on a destructive plate boundary- the North American plate (denser) subducted by the Caribbean plate
  • Convection currents pulled the North American plate into the mantle-> heat+ friction -> the rock melted-> molten rock was lighter than the surrounding rock-> rose through cracks towards the Earth's surface-> volcanic island
  • Chances Peak Volcano erupted+ produced thick sticky lava (andesite)-> builded up at the top of the volcano in a dome-> became too heavy-> the dome collapsed-> huge ash cloud formed
  • The ash cloud rose to a height of 10km
  • The dome collapsed-> rocks, gases+ ash were ejected from the volcano-> pyroclastic flows (fast moving+ destroyed everything on their path)
  • Strong winds blew the clouds of ash westwards over the island

Effects

  • Suffered blackout conditions- due to the sun being obstructed by the ash cloud
  • The eruption of the volcano should not have had a major impact on the people, as the areas affected were in the Exclusion Zone set up after an eruption in 1995. But on 25 June, 1997 some authorised people were in the Exclusion Zone to carry out essential tasks+ monitor the volcanic activity. An eruption looked likely-> the workers evacuated safely by responding to the emergency sirens. However, some unauthorised people, who were in the Exclusion zone, were too far away to hear the sirens. They thought they would receive audible warning from the volcano as it was going to erupt-> this didn't happen-> were caught unawares
  • 19 people killed by the pyroclastic flows
  • 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
  • The villages of Farm and Trant- completely buried by ash flow deposits
  • The ash fell back on to some parts of the island-> deposited ash 2-3 mm thick
  • A total of 4 km2 of land was covered by deposits
  • Houses in the Exclusion Zone destroyed by impact of rock, up to 5m in size-> should have been empty, but 15 people were living in the Exclusion Zone-> mostly farmers-> were producing crops to feed evacuees
  • The pyroclastic surges spread out+ flattened trees on the ridge surrounding Farrell's Yark-> no vegetation was left, just bare vegetable beds+ the soil was baked hard

Overall summary

-25 June, 1997-Chances Peak Volcano -Produced thick sticky lava- andesite

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