Hostile World: Mt St Helens Flashcards
Economic effects
27 bridges destroyed (social too) $1.1 billion lost Livestock lost Increased tourism Unemployment Disrupted air travel 185km road destroyed Ash blocked car & plane engines
Social effects
57 dead
People had to evacuate
200 destroyed homes
Respiratory probs
Environmental effects
370sqm land destroyed Day into night 17 mile radius engulfed 156 tons of timber brought down 12% crops ruined Mt height reduced by 390 m Forest fire Soil fertility
Where is Mt St Helens
CASCADES Mt Range
State of Washington
North West of USA
When did Mt St Helens erupt?
May 18, 1980
Strength of eruption
27 000 Hiroshima Bombs
Type of plate boundary
Destructive plate boundary
Plates involved
Juan de Fuca — oceanic
N. American Plate — continental
When us the last eruption?
1857, 123 years before
Signs it was to erupt?
Dome at the side
•build up of earthquakes between March — May
•plumes of ash
Cause of bulge at the side
Crater vents blocked by previous eruption
•magma diverted on the north — cryptodome
•grow 6ft/day
What trigger the eruption ?
5.1 earthquake caused landslide
•magma released from the bulge
Main hazards of eruption
Landslide Gas escaping, multiplying factor 22x Pyroclastic flow 700m/h Smoke & ash Lahar
What was done to reduce the effects of the eruption?
- 20 mile exclusion zone
- scientific instruments
- map zone techniques
- volcanologists observing
- media coverage
- people awareness
How were the effects reduced: before
Monitoring Scientific instruments Exclusion zones Evacuation News reports
