Volcanoes –
Friend or Foe?
What are the effects of
volcanoes on man and the
environment?
Mt St Helen’s Eruption (May 1980)
Mt St Helens
located on the ‘Ring
of Fire’
Mark Mt St Helens on your map of where volcanoes and earthquakes are located.
Mt St Helens - Causes of the Eruption
Juan de Fuca plate
North American Plate
Which is the oceanic plate?
Task 2: Describe how a volcano is created in 2 sentences.
Mt St Helens - The Eruption
Video: Mt St Helens
• Make notes about the effects of this
volcanic eruption on people.
Mt St Helens
AFTER
BEFORE
Mt St Helens
Consequences of the Eruption
N
O
10km
What damage did the eruption cause?
Up to 70mm of ash falls across Washington and East Montana…7000 school
students have an early Summer vacation due to problems on the roads
Two million
birds, animals
and fish are
killed.
Deer mice,
chipmunk,
vole, gophers,
salamander
survive the
blast.
Mudflows block
and divert rivers.
Hot mudflows raise
the temperature of
the rivers to 30ºC
60 people die from
the eruption.
The post office and
Lone Fir Motel shut
down in Cougar.
Damage to
crops $175
million
More tourism
Less tourism
Communications
threatened – railway
and road bridges
destroyed, Portland
harbour blocked
Gophers, through their
tunnelling, mix the soil with
the ash. This increases the
fertility of the soil.
Separate the above into the short term and long term impacts of the eruption.
Homework: Due:______
• What are the affects of a volcanic eruption
on people? Give examples.
• Write about 100 words to answer the
above question.
Homework review:
Hot spot volcanoes - Hawaiian Islands
Active volcanoes
Extinct volcanoes
Hot spot
In the diagram above, why are the volcanoes
to the right of the ‘hot spot’ extinct?