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Case Study: Mount St. Helens Volcanic Eruption (Economic Impacts (Airports…
Case Study: Mount St. Helens Volcanic Eruption
Mount St. Helens in Washington (USA) is one of several volcanic peaks in the Cascade mountains.
The cascade mountains are above a destructive plate margin, where the Juan de Fuca plate is being forced under the North American plate.
Mount St. Helens is a composite volcano.
On 18th May 1980 there was a large earthquake of magnitude 5.1 followed by a massive eruption of volcanic material - including rocks, ash, hot gases, steam and lava.
Pyroclastic flows, lahars and floods (due to material being dumped in rivers and lakes, displacing water) were caused by the eruption.
Economic Impacts
Airports were temporarily closed (some for up to 2 weeks) because of reduced visibility. Over 1000 commercial flights were cancelled.
A lot of money had to be spent on clearing ash from roads and runways e.g. it cost $2.2 million to clear the ash in Yakima (a city 135km from the volcano.
Over 200 homes and cabins were destroyed and many more were damaged.
27 bridges, 24km of railways and around 300km of roads were destroyed.
The total cost of the damage was around $1.1 billion.
River traffic and shipping was disrupted and 31 ships were stranded because mudflows dumped huge amounts of sediment in rivers.
The timber industry was severely affected by the destruction of forest.
Social Impacts
Unemployment rose tenfold at first - although this did return to normal once clean-up operations began.
Social facilities and recreational sites were destroyed.
Hundreds of people lost their homes.
Some people experience emotional stress.
57 people were killed - mostly by inhaling volcanic ash.
Environmental Impacts
Sediment dumped in Spirit Lake raised the lake bottom by over 90m and the water level by over 60m.
Water quality was temporarily reduced.
Wildlife suffered - around 7000 big game animals and many thousands of birds and small mammals were killed. Around 12 million young salmon were also killed.
Almost 240km squared of forest was destroyed.
Responses
Ash clean-up operations were organised - around 900,000 tonnes of ash were removed from roads, buildings and airports.
Emergency shelters were set up for stranded and homeless people.
Shipping channels were cleared of sediment to restore shipping and some new channels were cut.
Face masks were distributed in some areas to protect people from breathing in ash.
45,000 acres of land have been replanted with more than 18.4 million trees.
Emergency responses were conducted by FEMA (Federal Emergency Management Agency) and involved both national organisations (e.g. the US Army Corps of Engineers) and local services.
Domestic water supplies were monitored to ensure that they weren't contaminated.
Good management meant that hazardous areas were evacuated.
USGS scientists issued warnings to people living in the area and made recommendations about the locations of hazardous zones.
Based on these recommendations, in March access to the volcano was restricted and the evacuation of around 2000 people was started.
When the earthquakes began in March, the USGS (United States Geological Survey) started a round-the-clock monitoring system. It included gathering seismic data and measuring the rate of bulge growth, ground temperature and sulphur dioxide gas emissions. Volcanic and seismic activity reports were issued daily.
Despite the monitoring data, scientists couldn't accurately predict the eruption - on the day of the eruption there were no unusual changes that could be taken as warning signs.