Where is Mount St. Helens located?
Washington, USA
When did Mount St. Helens erupt?
May 18th 1980
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Where is Mount St. Helens located?
Washington, USA
When did Mount St. Helens erupt?
May 18th 1980
Why did Mount St. Helens erupt? What caused the eruption?
the Juan de Fuca plate (oceanic crust) subducted underneath the North American plate (continental crust) into the mantle
destructive oceanic-continental plate boundary
magnitude 5 earthquake underneath the volcano at 8:32am
What were some primary effects of the eruption?
61 deaths
every form of life within a 25km (17-mile) northwards blast zone range of the volcano was destroyed
370 square miles of surrounding area destroyed
tens of millions of trees destroyed
250 homes destroyed
15 miles of railways destroyed
185 miles of highway destroyed
400 metres blown off the top of the volcano
47 bridges destroyed
12 million salmon died
approximately 7,000 animals died
logging camps destroyed
largest landslide ever recorded
at least 12 US states were affected by ash fallout
What were some secondary effects of the eruption?
electricity supplies interrupted
telephone wires cut
12% of the total crop was ruined by settling dust
£100 million ash damage cost to farmers’ crops and machinery
the timber industry in the area was destroyed by the flattening of trees
traffic chaos caused by the ash ejected into the atmosphere
What were some immediate responses to the eruption?
set up a 20-mile exclusion zone on March 31st 1980
declared a state of emergency on March 31st 1980
immediate search and rescue operation
helicopter rescues to take casualties to hospital
rescued 198 people
shelter provided for those who lost their homes
medical supplies given to the injured
flights cancelled due to the ash ejected into the atmosphere
What were some long-term responses to the eruption?
created the Johnston Ridge Observatory, which was opened in 1997
money given to redevelop the salmon hatcheries
a million tonnes of ash were removed from roads, buildings, and airports
cost of over $1 million to remove ash
ash removal in the town of Yakima took 10 weeks
built new highway
money give to rebuild houses
forest area to the north replanted (millions of trees replanted, costing $300 million)
How is Mount St. Helens being managed now?
seismic monitoring stations
accelerometers
GPS stations
gas sampling stations
electronic tiltmeters