Mt St Helens case study


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A-level case study on the 1980 eruption of Mt St Helens

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Mt St Helens case study

  1. 1. Mt. St. Helens is located in the North West of the USA inWashington State.It is part of the Cascade Range of mountains.The area around the mountain is a National Park which ismainly used for tourism, forestry, salmon farming and someagriculture – therefore the population density of the area isrelatively lowBefore 1980, Mt St Helens hadn’t erupted for over 100 yearsThe USA is an MEDC (and was in 1980) – with a GDP percapita of over $25,000 (in 1980)Mt. St. Helens is a typical composite cone volcano - formed ona destructive plate margin where the Juan de Fuca plate isbeing subucted under the North American plate.
  2. 2. From the spring of 1980, scientist startedto record 100s of small earthquake tremorscoming from the mountain.In March there were small eruptions ofstream and ash from the volcano.These events attracted a large number ofnews reporters and tourist to the area.By early May there was a visible bulge onthe northern flank of the volcano wheremagma was being pushed to as a result ofa volcanic plug that had formed in the mainvent.At 8:32 am on Sunday 18th May 1980 theeruption began following the sequence ofevents shown on the diagram opposite.As well as the landslide, lateral blast,pyroclastic flows and ash cloud, the heatfrom the eruption melted snow whichcovered the mountain creating lahars (asecondary hazard)
  3. 3. Social Economic Environmental56 people were killed within Several logging camps were Spirit Lake was filled in by thethe blast zone destroyed landslideLahars destroyed over 200 12% of the total crops in the 250km² of forestry washomes, 27 bridges, 185 miles area were damaged or destroyedof road and 15 miles of destroyed – fruit trees were Out of 32 known species ofrailway – severely disrupting particularly badly affected small mammals living in area,communications Estimated short term only 14 are known to haveSince the eruption, the tourist economic losses in survived (mainly burrowingindustry has grown due to the Washington State reached mammals such as gophers)fame of the eruption over $800 million – have of Over 250km of river which was made up from the ecosystem was destroyed by loss of forestry. The second the lahars – killing all fish life biggest cost was that of the Over 7,000 big game animals clean up operation $250 were killed (elk etc.) million Flood risks were increased on the Toutle and Cowlitz river as their channels were choked with mud and debris.
  4. 4. Management:An exclusion zone was set up from the middle of March with red zones where no activity wasallowed and blue zone where certain activities could take place such as essential farming andforestry work. In total, 2000 people were evacuated from the area.There was however a lot of public opposition to the exclusion zone and people regularly tried toevade to road blocks to get closer to the volcano.Responses:Immediate Long termThe National Guard flew helicopter rescue The Toutle, Cowlitz, and Columbia Rivers weremissions into the blast zone for 2 weeks and dredgedrescued 130 people. Over 10 million trees were replantedThe National Guard also issued clean water, The bridges were rebuilt with a wider span inemergency food rations and medical supplies an attempt to avoid blockages from future2 million gas masks were provided by the laharsFederal Government to help prevent The volcano is now monitored constantly byrespiratory problems the USGS and clear plans have been made toThe ash was cleared from towns such as prepare and warn people in the area beyondYakima within 3 days the immediate blast zone to make them aware of the risks of ash clouds