Case Studies Flashcards
Where is the volcano Mt St Helens situated?
In North America in Washington state USA and it is part of the Cascade Range Mountains.
When did Mt St Helens erupt?
18th of May 1980.
Why was the Mt St Helens eruption so catastrophic?
It was the largest and worst eruption ever to hit the USA.
Why did Mt St Helens erupt?
Mt St Helens lies on a destructive plate boundary where the Juan de Fuca plate is subducted underneath the North American plate. The Juan de Fuca plate is subducted into the mantle because of convection currents in the mantle, the Juan de Fuca plate then is melted and rises through cracks in the crust causing an eruption. The eruption was triggered by a magnitude 5 earthquake.
How did the Mt St Helens eruption effect the landscape?
Pyroclastic flows killed every plant and animal within 25km north of the volcano - approx 7000 animals died.
Pyroclastic flows caused every tree within 30km of the volcano to be flattened.
Lahars covered a vast area choking rivers and 12 million salmon died.
Destroyed 250 homes, 47 bridges, 15 miles of railways and 185 miles of highway.
How did the Mt St Helens eruption effect the people and the economy?
57 people died - mostly from poisonous gasses or by suffocating on ash.
The cost of ash damage to farmers crops and machinery totalled £100 million.
15cm of ash fell causing traffic chaos and airline flights to be cancelled.
The timber industry in the area was destroyed by the flattening of trees which cause unemployment.
Local water supplies were contaminated with ash.
What was the short term aid after the Mt St Helens eruption?
The national guard and state troopers rescued stranded people.
Providing shelter for those who lost their homes.
Giving medical supplies to those who were injured.
The authorities were able to mobilise the emergency services quickly to help those in need.
The operation rescued 198 people.
What was the long term aid after Mt St Helens?
A million tonnes of ash were removed from roads, buildings and airports.
Removing the ash cost over $1 million in the town of Yakima and it took ten weeks.
Millions of trees were replanted because there was a huge loss of timber which would cost $300 million.
Compensation was given to farmers who’s crops had been destroyed by ash.
New tourist facilities were built because there were less tourists, meetings and conferences in the area after the eruption.
Money was given to build a new highway and also to rebuild houses that were destroyed.
In total there was $1.1 billion of property damage.
What time period did Montserrat erupt in?
1995-1997.
What happened at Montserrat?
A volcanic eruption that sounded like a jet engine.
Scientists arrived to study the volcano (it had lay dormant for centuries)
9 seismometers were installed
1 month after first eruption ash and mud shot 2km in the air
Everything was covered in ash (ash Monday)
Lava dome started to build.
Pyroclastic flows
Blasts destroy village
1.8 m diameter boulders
Tilt meters were installed
Lava dome grew
Radios broadcast
Alarms activated.
Why did Montserrat erupt?
Destructive boundary, subduction zone, North Atlantic plate under Caribbean plate.
What were the impacts of Montserrat eruption?
A lot of people evacuated (80% of pop lived in Plymouth)
Crops and homes destroyed
A lot of ash damage.
What were the responses to the Montserrat eruption?
6,000 people were evacuated by government and British army.
The housing for evacuees was basic and started to become squalid.
Volcanologists were brought in.
The airport was closed
A temporary port was opened.
