Mount st Helens


Key facts:

- Mount st Helens in Washington is one of the volcanic peaks in the cascade mountains 

-cascade mountains- above destructive plate margin, Juan de fuca plate forced under north american plate 

-composite volcano 

-1980 March-signs of an eruption including earthquakes, bulge on side of volcano, ash and steam 

-1980,18th May- large earthquake, magnitude of 5.1, a massive eruption of volcanic material 

-eruption covered 600km north of volcano-the blast zone 

-all vegetation/buildings destroyed in blast zone-30km

-pyroclastic flows, lahars, floods 

-eruption of ash/steam-540 million tonnes of ash

Economic impacts:

-total cost of damage-$1.1 billion

-200 homes/cabins destroyed 

-airports temporarily closed  due to


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