Mt St Helens Flashcards
Where
Washington state located on a destructive margin where the Juan de fuca plate is subducted under North American plate part of the cascade range in the ring of fire
Type of volcano
Composite
How did it occur
20th March 1980 earthquake 4.2 caused the northern flank to bulge
18th may another earthquake 5.2 caused the northern flank to collapse causing the largest landslide recorded on Mount St. Helens
What type of eruption and how long
Plinlan which lasted 9 hours
Nature of eruption
Lateral blast caused Avalanche and proycrlostic flow melted snow causing Lahars
How many airports closed
2
How far was affected by eruption
250m2 affecting 11 states with ash deposits
How many homes destroyed
200
How much forest
100,000 acres
How many killed
57 although this number could have been significantly higher but it was a Sunday so no one was working in the forest
Secondary
Lahars,
Unemployment,
Ash blocked rivers,
Sediment in river Colombia blocked barge
Long term
Tourism increased
Homelessness
Improved soil fertility
Stress and emotional
How much total cost
1.1 billion
How much crop land destroyed
12%
What equipment was used
Seismometers
Precise ground surface measurement to detected swelling
Aerial infrared to detected hot stops
