Unit 1: Topic 2 - Case Study 4 - Mt St. Helens (Composite Volcano)

Question 1

Where?

Answer 1

One of the 5 volcanoes in the Cascade Range in the Washington State, USA.

Question 2

When?

Answer 2

Pre-eruptions on 27th March 1980 (Phreatic (Steam) eruptions)

Eruption on the 18 May 1980 8.32am

Question 3

Why?

Answer 3

DESTRUCTIVE PLATE MARGIN (SUBDUCTION)

Juan de Fuca Plate (Oceanic) ->

Question 4

What?

Answer 4

BEFORE THE ERUPTION

• Before the eruption, there was a large bulge that could be seen in the volcano.

ASH

• Ash made the area pitch black and volcanic ash rained down on cities. Not particularly lethal but could be in the long term.
• Ash which fell into the river, raised the temperature and killed the fish. (SECONDARY)
• 12% of total crop was ruined by settling dust. Crops and livestock was lost due to flooding. (SECONDARY)
• Eruption produced approximately 1 cubic kilometre of ash.

LANDSLIDE

• 5.1 Richter scale caused landslide on North-East side of volcano.
• Landslide caused a 300ft tsunami
• Flash flood because the glacier on the volcano flooded.

OTHER

• The main eruption was followed by smaller eruptions. (SECONDARY)
• There were huge columns of gases throughout the day. (PRIMARY)
• Trees within a 25km radius were flattened (PRIMARY)

Question 5

Who?

Answer 5

LOSSES?

• 61 people died died from poisonous gases.
• Farmers lost crops
• Damage to peoples’ properties

WIN?
- Tourist industry recovered - 3 million visitors every year.

AID?
- Army helped rescue although unorganised.

Question 6

How?

• did people react?
• might things be different?

Answer 6

…MIGHT THINGS BE DIFFERENT?

• Used ‘spiders’ to monitor temperature, earthquake and monitor volcanic gases.
• Careful infrastructure and not building on roads of mudflows.
• Better predictions and idea of composite volcanoes
  
  • More knowledge to know how to react to volcanoes to evacuate quicker
• Animals predicted eruptions
• Scientists studied earthquakes using seismometers and studied geothermal energies. Scientists are also recording heights of lava domes and patterns.
• Remote-sensing instead people risking lives.

…DID PEOPLE REACT?
- Some refused to leave their homes and were thought to be ‘patriotic’ as they did not evacuate.