MOUNT ST HELENS, A VOLCANIC ERUPTION IN AN

MEDC (More Economically Developed Country)

Where is Mount St Helens? Mount St Helens is

a volcano in north west USA.

It is in the Cascade Mountains which are FOLD mountains T

he

Cas

cad

es

Mt St. Helens

Mt St Helens – causes of the eruption

Juan de Fuca North American Plate

Mt St HelensLocated in the USA

Mt St Helen’s eruption (May 1980)

JUAN DE FUCA PLATE

NORTH AMERICAN PLATE

DESTRUCTIVE PLATE BOUNDARY

Internet Linkshttp://volcano.und.nodak.edu/vwdocs/msh/msh.html

Mt St Helens is located on a destructive plate boundary where a continental plate (North American) meets an oceanic plate (Juan de Fuca).

Juan de Fuca plate North American plate

Which plate is denser?Describe what happens when the oceanic plate descends under the continental plate.

Mt St Helens – causes of the eruption

Mt St Helens – the eruption

WATCH VIDEO CLIP OF MOUNT ST HELENS ON FROG WEBSITE

BEFORE

AFTER

MOUNT ST HELENS, USA

DESTRUCTIVE

JUAN DE FUCA AND NORTH AMERICAN PLATE

N

0 10km

Mt St Helens – consequences of the eruption

Hot mudflows raise the temperature of the rivers and lakes to 30ºC

Two million birds, animals and fish are killed.

60 people die from the eruption.

Up to 70mm of ash falls across Washington … 7000 school students have an early summer vacation due to problems on the roads

Mudflows block and divert rivers. The US army takes 18 months to dig out the debris from the River Toutle.

Communications routes threatened – railway and road bridges destroyed, Portland harbour blocked

A decrease in tourism

What damage did the eruption cause? Short termOr long term?

The post office and Lone Fir Motel shut down in Cougar.

Damage to crops=$175million

This lava is weathered (broken down) to form a fertile soil,

Tourists are attracted to areas of volcanic activity.

Geothermal energy (heat from the earth) can be produced in many volcanic areas.

Why do people live in volcanic areas? ADVANTAGES:

Minerals eg sulphur

Why do people live in volcanic areas? DISADVANTAGES:

• Explosions and eruptions cause:

1. Dangerous gases

2. Loss of life

3. Loss of homes, animals, wildlife, trees and crops

4. Disease and fires

5. Avalanches, mudflows and floods