Mount St Helen Case Study

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  • Created on: 22-05-13 10:48
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Mount St Helens, 1980:
Low population density around volcanoe
Composite cone volcano lying on a destructive plate
margin (North America and Juan De Fuca Plates)
Before eruptions, there were hundreds of tremors felt
In March there were eruptions of steam
and ash
In May: There was a large bulge on the northern flank of
volcano due to a volcanic plug
Erupted on 18th May 1980 and this created snow to
melt leading to lahars
150 cubic metres of material was deposited
An evacuation zone of 5 miles was set up
56 people were killed in the blast zone
12% crops in the area were damaged ­ creating a loss of $800m
Lahars destroyed 200 homes/27 bridges/185 miles of roads/15 miles of railway
Spirit Lake was filled in with volcanic output
250km² of forestry was destroyed
250km of river ecosystem was destroyed
Large flood risks were warned
Roughly 24,000 animals died
Helicopter rescue missions saved 130 peoples lives
National Guard issued clean water, emergency food rations and medicine supplies
2 million gas masks were provided for people in surrounding areas
Ash was cleared from most towns within 3 days
The tourism industry eventually began to grow due to the eruption
The clean-up operation cost around $250m
Touth, Cowlitz and Columbian rivers were dredged of sediments
Over 10million trees were replanted
Wider spaced bridges were built
The volcano was even more closely monitored than beofre


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