Mount St Helens

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  • Created by: Ruth
  • Created on: 12-05-14 19:33
Explosion
Paroxymal explosion, VEI 5, acidic magma
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Pyroclastic flow
up to 800C, 200km/h, volume of 1km^3
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Where?
180km South of Seattle
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Social
Highly concentrated devastation in a remote area - 57 killed, 200 homes destroyed
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Economic
Railway bridge washed away (flooding due to ash), 47 road bridges destroyed, top class salmon and trout rivers lost, fish hatchery destroyed, $3 billion damage
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Environmental
Spirit Lake filled in to a depth of 60m, every tree within a 250km^2 area destroyed, widespread flooding, Columbia River disrupted by extra sediment, 540 million tonnes of ash over 60,000km^2
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When?
May 18th 1980
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Cost
$363 million to clean up, damage of $3 billion
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Evacuation
Exclusion Zone designated as uninhabitable, National Guard rescued 130 by helicopter, 2000 evacuated and issued with clean water, food rations and medical supplies, 2 million gas masks
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Evaluation
Funding is adequate, + prepared emergency services. People thought the government over reacted, so tried to get around road blocks
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Removing ash
ashfall disrupted infrastructure: Interstate 90 closed, 1000 flights cancelled. 900,000 tonnes of ash removed from highways, cost $2.2 million and took 10 weeks in Yakima, WA. Into old quarries, landfill or greenfield, grass planted to stop wind
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Small scale ash removal
Companies in Portland fined if ash not removed
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Early Warning System
Since 2005, USGS used a National Volcano Early Warning System, using hi-tech prediction on Mount St Helens and 168 other volcanoes. The Cascades observatory issues warnings as soon as change is detected
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Other cards in this set

Card 2

Front

Pyroclastic flow

Back

up to 800C, 200km/h, volume of 1km^3

Card 3

Front

Where?

Back

Preview of the front of card 3

Card 4

Front

Social

Back

Preview of the front of card 4

Card 5

Front

Economic

Back

Preview of the front of card 5
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