1. VIOLENT VOLCANOES…

2. What is a volcano?
A volcano is an opening or vent in the earth’s surface
through which molten material erupts and solidifies as lava.
Volcanic vent
http://www.youtube.com/watch?v=NBPwwt0HuVo&feature=fvst

4. Label this cross section of a volcano
Volcanic
Crater bombs, ash,
lava, gases
Parasitic
cone
Main vent
•Volcanic bombs,
ash, lava, gases
•Magma chamber
•Parasitic cone
Magma •Crater
chamber
•Main vent

5. What comes out of a volcano?

6. Do all volcanoes erupt?
Active volcano – liable to erupt
e.g. Mt Etna & Mt. Merapi in
Indonesia.
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. http://www.bbc.co.uk/learningzone/clips/volcanic-scotland/9116.html
However, it is often very difficult to tell whether a volcano
will erupt again…El Chichon, Mexico erupted in 1982
after being dormant for approximately 1200 years!

7. Why do they happen?
Can you remember what is happening to the plates at a
CONSTRUCTIVE plate boundary?
The two plates are moving apart…
What comes up through the gap created in the crust?
A volcano….
Volcanoes at constructive plate boundaries don’t tend to be very
spectacular or explosive. As the crust moves apart for the
magma it is easily able to escape and just trickles out the top.
The lava here tends to be runny and flows some distance from
the crater before it solidifies. So, these volcanoes tend to be
shallow sided, or SHIELD volcanoes.

8. Volcanoes also form at DESTRUCTIVE plate boundaries.
Where one plate is forced down under the other (called subduction).
What happens to the crust that is forced down into the mantle?
It melts…
What does this create?
Excess magma…
What do you think happens to this extra magma?
Pressure builds and eventually there is a violent, explosive, volcanic eruption!
Volcanoes at destructive plate boundaries tend to be very explosive! The lava is thick
and so does not flow far from the crater. These volcanoes build up layers with each
eruption. These are called COMPOSITE volcanoes.

9. Example of a shield volcano- Mauna
Kea, Hawaii

10. Example of a composite volcano- Mt.
Merapi – Indonesia

11. Where in the world are volcanoes found?
Around which plate do we find most volcanoes?

12. Where do Earthquakes and volcanoes form?
The ‘ring of
fire’ is an
area around
the Pacific
Ocean, prone
to A map to show the
earthquakes Ring of fire
spread of Earthquakes
and and volcanoes around
volcanoes the earth

13. The Ring of Fire

14. Hawaii
The Hawaiian islands are a chain
of volcanoes in the Pacific Ocean.
Look at their location on the map below.
Why is this an unusual place for them to
be located?

15. Hot spot volcanoes
In the animation above, why are the volcanoes to the left of
the ‘hot spot’ extinct?

16. HOT SPOT volcanoes are found in the middle of a plate.
Here the crust is weaker than usual. There is a plume of hot magma rising from
the mantle and it is able to push through the crust at this point.
The plate moves across this ‘hotspot’ forming a chain of volcanoes over millions
of years e.g. Hawaii.

19. Your tasks:
• You have one side of A3 paper on which to
produce a ‘fact sheet’ about volcanoes. You
need to include:
1. Completed ‘pop-up’ volcano.
2. An explanation as to how volcanoes form. Try
to include information about both constructive
and destructive plate boundaries and what the
different volcanoes are known as (shield and
composite).
3. An explanation as to what is meant by active,
dormant and extinct volcanoes.
4. An explanation of ‘hot-spot’ volcanoes.