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Geography Case Studies
Volcanoes…read more

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Mount St. Helens
May 18th 1980…read more

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Location and Hazard
· In the Cascade mountains
· A composite volcano with andesitic lava
· Destructive plate boundary ­ Juan de Fuca and North American plates
· In March 1980 there were a series of small earthquakes and a bulge
· On May 18th there was a 5.1 magnitude earthquake followed by an
eruption of volcanic material ­ rock, ash, steam and hot gases
· The lateral blast covered an area of 600km² north of the volcano
· Pyroclastic flows, lahars and floods
· 540 million tonnes of ash deposited across an area of 57,000 km…read more

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Social Impacts
57 killed, including
200 homes Unemployment rose
a volcanologist and
destroyed tenfold
Harry Truman
Social facilities were
lost e.g. impossible
to fish in Spirit Lake
(filled with toxic
gases)…read more

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Environmental Impacts
Out of 32 small
mammal species,
240km² of forest 7,000 big game
only 14 are known
was lost animals died
to have survived
(burrowing animals)
Sediment in Spirit
Lake raised the
bottom by 90m…read more

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Economic Impacts
$2.2 million
24km of railway
It cost $1.1 spent clearing
and 300m of
billion up ash in
road destroyed
Timber industry Airports shut for
affected as 2 weeks and
240km² of 1000 flights
forest destroyed cancelled…read more

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