Download Volcanoes

Volcanoes
Plate Tectonics
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What is a volcano?
Why do volcanoes occur?
Where are volcanoes found?
Contents
A case study: Mount St Helens
Can eruptions be predicted?
Why do people live in volcanic areas?
Summary activities
The key concepts covered are:
Place, Space and Physical and human processes.
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Whatisisaa volcano?
volcano?
What
By the end of this section, you will:
Know what a volcano is
and what happens beneath
the surface of a volcano.
Understand about the
different types of volcano
that exist.
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What is a volcano?
A volcano is an opening, or vent, in the earth’s surface.
Volcanic vent
This opening allows molten lava to erupt through it and
solidify as igneous rock. Other materials are also ejected.
What happens beneath the surface to
cause an eruption?
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Inside a volcano
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Cross section of a volcano
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Cross section of a volcano
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Volcanic production
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Volcanic emissions
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Volcanic emissions
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Volcano types
There are three different types of volcano. Geographers call
the categories active, dormant or extinct.
An active volcano is liable
to erupt at any time,
e.g. Mt Etna.
A dormant volcano has not
erupted for years. Mt
Pinatubo erupted in 1991
after 500 years of dormancy.
An extinct volcano has not erupted for a very long time
and is unlikely to erupt again, e.g. Edinburgh.
Categorizing volcanoes can be tough. Chaitén in
Chile erupted in 2008 for the first time since 7400BC!
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What type?
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Why do volcanoes
Why do volcanoes
occur?
occur?
By the end of this section, you will:
Know more about how plate
tectonics cause the formation
of volcanoes.
Understand the role
destructive and
constructive boundaries play
in the formation of volcanoes.
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Plate movements
The surface of the Earth is covered in plates that are in
constant motion.
The motion of
the plates can
cause problems
to the surface of
the Earth.
Most of these
problems occur
at plate
boundaries.
A plate boundary is where the edges of two plates meet.
The vast majority of the Earth’s volcanoes can
be found on a plate boundary.
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Important boundaries
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Destructive plate boundary
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Constructive plate boundary
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Volcanic activity at plate margins
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Where
volcanoes found?
Where
areare
volcanoes
found?
By the end of this section, you will:
Be able to recognize the
areas of the Earth where
volcanoes are usually found.
Know what is meant by the
term ‘Ring of Fire’.
Know what is meant by a
hot spot volcano.
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Where are volcanoes found?
Volcanoes are usually found at plate boundaries.
One area of the world is
well-known for the number
of volcanoes around it.
This area is known as
the ‘Ring of Fire’.
The Ring of Fire is located
around the Pacific rim.
Can you think of any volcanoes that are
located on the Ring of Fire?
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The Ring of Fire
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Hawaii
The Hawaiian islands are a chain of volcanic islands that are
situated in the
Pacific Ocean.
Why is this
an unusual
place for
them to be
located?
Most volcanoes are located on plate boundaries. Hawaii is
nowhere near a plate boundary.
Why are the Hawaiian islands volcanic?
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Hot spot volcanoes
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A casestudy:
study – Mount
Mount StSt
Helens
A case
Helens
By the end of this section, you will:
Have a better understanding
of what happened in the
Mount St Helens eruption.
Understand what some of
the consequences of the
eruption were.
Realize what damage the
eruption caused.
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Mt St Helens – the eruption
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Mt St Helens – consequences of the eruption
The effects of the Mount St Helens eruption were enormous.
The pyroclastic surge spread
27km from the volcano and
flattened acres of woodland.
Ash clouds stretched 26km above
sea level.
However, there were some positives.
Some plants and animals were
resilient enough to survive.
The lack of human interference
encouraged nature to spring
forth again.
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How great was the damage?
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Back to the future
What does the future hold for Mount St Helens?
Since 1980, there has been more activity on Mount St Helens.
Between 1980 and 1986 a new
lava dome was formed.
Magma reached the surface of
the mountain in October 2004.
In 2005, a 36,000 foot plume
of steam was emitted. There
was also a small earthquake.
It seems likely that Mount St Helens will erupt
again in the future. Will we be able to tell when?
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Can eruptions be predicted?
Can eruptions be predicted?
By the end of this section, you will:
Know what a
volcanologist does.
Understand some of the
difficulties that are
associated with predicting
volcanic eruptions.
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The problem of prediction
Volcanologists – people who study volcanoes – are skilled
at predicting the likelihood of an eruption.
However, it is difficult to pinpoint
when an eruption will happen.
The movement of magma
may be detected, but often
no eruption occurs. Instead
it cools below the surface.
Monitoring potential
eruptions is expensive.
With many volcanoes erupting only every few hundred years,
it's not possible to monitor every site.
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Predicting eruptions
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Why
do people
live in volcanic
Why
do people
live in
areas?
volcanic areas?
By the end of this section, you will:
Know why people are
attracted to live near
volcanic areas.
Realize some of the pros
and cons of living
alongside a volcano.
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Why do people live in volcanic areas?
Although volcanic areas are exceptionally dangerous, there
are still a lot of people who live in zones that are affected by
volcanic eruptions. Why?
Tourists are attracted to areas of
volcanic activity. This provides
money for the local economy.
The lava produced by the volcano
is weathered (broken down) to
form a fertile soil. This is perfect
for growing crops.
Geothermal energy can be
produced in many volcanic areas.
Can you think of any other reasons?
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Pros and cons
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Summary
activities
Summary activities
By the end of this section, you will:
Know the key points of
volcanoes and volcanic
eruptions.
Understand important
words and phrases relating
to volcanoes.
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Summary quiz
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Glossary
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Anagrams
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