Mt St Helens Geography Case Study
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Transcript of Mt St Helens Geography Case Study
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Natural Disasters
Mount St Helens
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Location: Mount St Helens,
Skamania County,
Washington
Date: May 18th 1980
Time: 8:32 am
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Location
Mount St Helens is an active volcano in Washington in the North-west of the
United States.
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What happened?
On the 18th May 1980 at 8:32 am, an earthquake caused the entire north face of
the volcano to collapse spewing red-hot lava and volcanic ash over the surrounding
land.
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Why did it erupt?
Mount St Helens is situated on a destructive plate boundary between two tectonic plates:
the North-American and Juan de Fuca plates. As the Juan de Fuca plate is a less dense
oceanic plate, it slides under the North-American plate and melts. The molten magma then rises through the North-American plates to form the Cascade Mountain range which
Mount St Helens belongs to.
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magma
Juan de Fuca plate
North-American plate
Mount St Helens
plate melts
magma rises
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Why did the eruption occur?
The magma from the melted plate rose to the crust and eventually enough built up to cause earthquakes and eventually to blow the top off Mount St Helens. This was the eruption.
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Consequences of the eruption
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PrimaryEconomic:• “most economically destructive volcanic
eruption in the history of the United States”.
• 15km3 timber destroyed
• Agriculture downwind of volcano suffered (e.g. 12 million salmon died when their hatcheries were destroyed)
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Primary
Social:
• 57 people killed
• 200 homes destroyed
• 300km of main roads destroyed
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PrimaryEnvironmental:• 60 000km2 covered with volcanic debris• Wildlife (deer,elk, bear, birds and small
mammals) damaged- estimated 7000 big game killed.
• Landscape said to be “more desolate than the moon”.
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SecondaryEconomic:• Overall cost estimated $1.1million• Tourism trade dipped• Commercial flights cancelled from airports for 2
weeks• Timber industries suffered• Jobs lost in area• But tourism did increase in the long term
providing more jobs
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SecondarySocial:• People moved away from neighbourhood• Residents left without some amenities for a while
(e.g. Water treatment, electricity and sewage removal damaged)
• Residents suffered emotional and stress problems
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SecondaryEnvironmental:• Local ecosystem unbalanced• Water polluted by volcanic debris • Much of landscape is still scarred today• But the soil in the surrounding area became
more fertile
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