Download Volcanoes - Types and structure

Figure 1
1. Name the plate boundary in
figure 1. (1 marks)
2 .Describe the movement that
occurs at this plate boundary (2
marks)
3 .Name one other boundary
which can create a volcanic
eruption. (1 marks)
Volcanoes
Learning objectives
• To describe how volcanoes are formed
• To develop a greater understanding of the
structure of a volcano.
• To be able to identify and explain the different
types of volcano.
A volcano is an opening or vent in the earth’s surface through
which molten material erupts and solidifies as lava.
Active volcano – liable to erupt e.g. Mt Etna
Vent
Dormant (sleeping) volcano – a volcano
which has not erupted for many years. For
example, Mt Pinatubo erupted in 1991 after
500 years of dormancy.
Extinct volcano – a volcano which has not
erupted for many thousands or millions of
years e.g. Edinburgh.
Why might a volcano become extinct?
http://www.youtube.com/watch?v=WgktM2luLok
In the back of your books you need to draw a
diagram of how you think a volcano looks on the
inside (internal structure).
Key words to label your diagram with:
Main vent
Crater
Secondary vent
Magma chamber
Lava flow
In the front of your books draw a copy of the
diagram with the correct labels.
A good example is the North
America and Eurasian Plate
creating Surtsey, Iceland.
These volcanoes are created at
constructive margins. This is
where two plates are moving
apart from each other and
magma moves to the surface
through the gap.
The emerging lava is more fluid
and therefore the shape of the
volcano is low and wide. This is
why it is called a ‘shield’ volcano.
The eruptions from these
volcanoes are generally
more gentle and can last
for several months.
An example is Montserrat formed by the
Caribbean and South American plate.
These are formed at destructive
margins where one plate slides
underneath the other.
A slab of ocean floor slides down
and is melted due to friction. This is
called the subduction zone. This
melted magma warms up slowly
and mixes with water and carbon
dioxide released from the rock.
The hot magma is more sticky rises
in violent eruptions to form steep
sided volcanoes.
Layers of ash and lava build around
the main vent to form a strato
volcano.
The eruption is explosive and rock molten
and solid flies from the volcano. This is
followed by gas and steam which forms huge
clouds called nees ardentes.
An example is Mauna Loa Hawii.
In places where the plate is particularly
thin, magma may be able to escape to
the surface.
As the plate continues to
move the volcano dies
out and a new volcano is
formed on another area
of the plate.
Hot spots can create chains of shield
volcanoes. They therefore have gentle
oozing lava.
You are to think about one fact you have learnt
this lesson. You are to turn this into a question
and stand behind your chair once ready.
E.g. Shield volcano eruptions are gentle.
BECOMES
Describe the eruption at a shield volcanoes?
Learning objectives
• To be able to explain how and why the Mt St
Helens eruption occurred.
• To assess the social, economic and environmental
impacts caused by the eruption.
• Located in the state of Washington in the
USA.
• Located on a destructive plate boundary,
where a continental plate (North American)
meets an oceanic plate (Juan de Fuca).
• It is a strato (cone) volcano.
• The volcano erupted in 1980.
• Deadliest and most destructive volcanic
eruption in the history of the continental
United States of America.
Watch the video closely and listen and look for
information to fill in on your case study sheet
http://www.youtube.com/watch?v=-H_HZVY1tT4&feature=related
Primary effects
Secondary effects
Sediment carried
downstream ruined
barge transport on the
Columbia River.
- 63 people were killed,
mainly by poisonous
gases.
- Hot ash and gas
destroyed forests and
logging camps.
Ash blocked rivers
destroying popular
fishing sites and
causing flooding. This
in turn destroyed crops
and livestock.
- Lahars (mudflows of
ash and water) covered
an extensive area
surrounding the
volcano.
Flooding destroyed
communications such
as road and railway
bridges.
• You will be in three groups of six
• In your groups, you will be assigned the task of
considering either the social, economic or
environmental impacts of the Mt St Helens eruption.
• You must familiarise yourself with the impacts,
becoming experts in your field.
• Three of you will be reporters, tasked with questioning
each group on the facts they have found out.
• Team A – You are local residents who live and
Social
work in the Mt St Helens area
• Team B – You are government officials – who
are concerned with the economic effects of Economic
the eruption
• Team C – You are employees of the
environmental agency
Environmental