Mt St Helens Flashcards
When was the eruption
18 May 1980
Where is Mt St Helens
In the South of the state of Washington
How many deaths
57
Height before eruption
9,677 feet
Height after eruption
8,363 feet
When did the volcano go dormant
1850
What economic activity was the most prevalent on the volcano
Logging
When did the volcano become slowly active
January 1980
What showed the growing pressure in the volcano
Bulge growing on North side due to magma rising from a fault
What was the impact of this growing threat on scientists and tourists
Scientists became highly concerned yet tourists were attracted
When was a state of emergency declared and why
3 April 1980
To keep the tourists away from the volcano
Who was allowed in the Red Zone
Law enforcement and scientists
Who was allowed in the wider Blue Zone
Loggers
Why was there anger around the danger zones
Some wanted stronger action (loggers wanting security and safety when working)
Some wanted less harsh restrictions (wanting to return home)
Magnitude of earthquake that triggered the eruption
5.1
What did the earthquake cause
Entire north side of the volcano slipped in the largest landslide in recorded history
How fast did the landslide travel
155mph
VEI
5
How much sulphur dioxide was released
1.5 million tonnes
Category
Plinian
Why was the affected area so much larger than predicted
The eruption was a lateral blast, so covered a huge amount of land to the north, rather than the predicted small area around the whole volcano
How much land did the pyroclastic flow destroy
600km²
How far away were some trees burned
Over 30km
What did airborne ash particles cause
Lightning, which triggered many forest fires
How high were the ash clouds
23km
Impacts of ash in the air
Pollution of water supplies
Killing livestock
Restricting air traffic
What did ash settling on glaciers cause
It liquefied them, causing jökulhaups to destroy property and many bridges
What happened with the jökulhaups?
They travelled 27km into the Columbia River
3,000,000m³ of material was transported
They blocked many rivers and damaged aquatic habitats
What was destroyed
200 homes
47 bridges
185 miles of road
15 miles of railway
Many forests
Recovery within a year
Many of the bridges and roads rebuilt
900,000 tonnes of ash removed from roads
Routes into other areas reestablished
Logging restarted
What happened in 1980 - 1986
Numerous smaller eruptions
What happened in the early 2000s
Lots of activity, with eruptions of steam and ash, as well as new lava domes forming in the crater of the volcano
How did scientists use the event
To research how plants and animals could recover after a disaster such as this
