Mount St Helens Earthquake
- Created by: JohnBarrington109
- Created on: 07-02-18 10:27
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- Mount St Helens Earthquake
- Background
- Mt St Helens is located in the North West of the USA in Washington State.
- Mount St Helens erupted on the 18th May 1980; it was the worst eruption to ever hit the USA.
- The
area around the volcano is a National Park.
- The population density of the area is relatively low.
- Causes
- Mount
St Helens is a volcano which lies near to as destructive plate boundary.
- The Juan de Fuca plate being subducted into the mantle is exposed to increased heat and friction causing the plate to melt.
- Mt St Helens magma chamber had been growing for over 100 years.
- The event turned out to be a lateral blast meaning more damage than expected was caused.
- The
trigger was a magnitude 5 earthquake underneath Mount St Helens on the 18th
May at 8:32am.
- The volcano then went to erupt ash and produce pyroclastic flows.
- Mount
St Helens is a volcano which lies near to as destructive plate boundary.
- What happened?
- On March 27th another earthquake led to a 65m carter opening on the summit, seismic events continued into April.
- April
the 3rd, the governor had declared a state of emergency.
- Ordered the evacuation of most of the citizens within five mile exclusion, consisting of two high risk zones,
- On
May 18th at 8:32am an earthquake of Richter scale magnitude 5.1
triggered the biggest landslide ever recorded.
- A mixture of rock, glacier ice and soil flowed as lahars into Spirit Lake causing waves 200m high.
- The valley filled with 100m of debris.
- Impacts
- The environmental impacts
- Melted 70 per cent of ice on Mt St Helens, resulting in a lahar mudslide travelling at 50kmph, sweeping up 20,000 trees.
- Ash burst out the sides and covered 575km of land with ash and rock.
- Volcanic
ash covered three states.
- Winds spread the ash around the whole globe.
- 400
metres was blown off the top of the mountain.
- Crater was left that was 500m deep.
- The social impacts
- Over 100 people ended up in nearby hospitals, with many suffering from extensive burns and broken bones.
- Overall 57 people died, 53 of these being located out of the exclusion zones, areas which were deemed safe.
- Ash that fell caused traffic chaos and airline flights to be cancelled.
- Crops were ruined and so the livelihoods of loggers were devastated with large areas of trees being flattened.
- The economic impacts
- The cost of ash damaged to farmers crops and machinery totalled £100 million.
- The lahar flow destroyed 27 bridges and 200 homes, and finally stopped 60km down river.
- Many local businesses closed temporarily, however more jobs were created once tourism began to improve.
- Disruption of imports and exports as Washington state airport was closed.
- Total cost of the damage was more than 1.1 billion US dollars.
- The environmental impacts
- Background
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