Transcript The Mt St Helens Eruption - Welcome to Think Geography

The Mt St Helens Eruption
May 18, 1980
Where is it?
• Mount St Helens in the
USA has been one of the
most covered volcanoes in
recent years. In 1980,
witnesses watched and
filmed as the volcano
erupted – killing people
and creating much disaster
and destruction
Mt St Helens is an active volcano in the Cascade Range of
the northwestern United States. After being inactive since
1857, the mountain erupted in May 1980, causing 57
deaths and extensive damage in southwest Washington
state
.
How do volcanoes erupt?
• All volcanic eruptions begin deep in the
earth. Magma (molten rock beneath the
ground) begins to become pressurised and
tries to push a path to the surface through
the other rock. Sometimes this causes the
top of the volcano to grow and to expand.
How do volcanoes erupt?
• Eventually the pressure and gas build up
within the volcano becomes too much and
the Volcano will blow its top
• The volcano will then send gas, dust,
volcanic bombs, ash and lava into the air
Pyroclastic flows
Within a few hours of the blast – hot mixtures of volcanic gas,
pumice and ash swept down the north flank of the volcano at speeds
of up to 100 miles per hour. The temp of these was more than 1200
degress Fahrenheit
North of the volcano these flows deposited pumice that is up to 60
feet thick
The blast from the volcano reached as far as 16 miles north of the
volcano. It spread over an area of about 150 sq miles
The blast stripped trees from hillsides as far away as 6 miles from
the volcano
Different Types of Volcano
Different Types of Volcano
Different Types of Volcano
Different Types of Volcano
Views of Mt St Helens
This is Mt Rainer
- a volcano close
to Mt St Helens
The destruction
Section through the volcano
Volcano world – the best volcano
site
• The best volcano web
site is
• http://volcano.und.nod
ak.edu/
• But also try my site
• http://website.lineone.
net/~timothy.manson/