Mt St Helens

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Mount St Helens ^ Case Study// Volcano

  • Cascade range in Washinton State, USA, one of five. 
  • March 1980, first signs of eruption;  first earthquakes ocurred, then steam filled with ash was erupted, an 8km exclusion zone was set up and tourist and residents were evacuated.
  • On 18th of May at 8;32am, an earthquake measuring 5.1 on the richter scale casued a landslide on the north-east side of the mountain, biggest landslide ever recorded and the sideways blast of pulverised rock, glacier ice and ash wiped out all living things  up to 27km north of the crater.
  • In the outer zone 500 year old cedars were uprooted, 57 people died- one of them was the volcanologist David Johnston, who was correct in his prediction of a lateral blast.


  • Immediate response; mobilising helicopters to search and rescue those in the vicinity of the catastrophic blast, it was clear that no-one in the vicinity would survive, tourists within the exclusion zone were caught up in mud flows or in the lateral


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