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Volcanoes
A2 Natural Hazards – Year 10
Lesson 5
Why do volcanoes vary?
What is a volcano?
How do they vary?
How do they form?
Key Question today is…
What sub-questions do we need to consider to answer the key question?
Starter:Unscramble these letters to identify the famous volcanoes…NTEA SEVVIUSU IFUJ AOKRKATA
What is a volcano?
A volcano is an opening (Vent) in the ground where magma forces its way to the surface.
Magma which reaches the Earth’s surface is called lava.
We usually find volcanoes at plate boundaries...
Volcanoes happen where…One plate is pushed under another
• Plates move towards each other:• Oceanic plate gets pushed under the continental plate
There is a lot of pressure build up where two plates push together…
This means volcanoes that happen here are…
ExplosiveHave steep
sides
There is usuallyLots of dust, ash,gases and debris
Volcanoes happen where…Where two plates pull apart • Plates move away from each other
• Magma rises between them, forming new ocean floor
When two plates pull apart they leave a ‘gap’ where magma
rises…Volcanoes that happen here are quite different…
Not very steep
Gentle eruptions because there is little pressure build up
Often happen under the sea, e.g. Mid Atlantic Ridge
Dead or just sleeping?
No eruption for
thousands of years
Has erupted recently and is likely to do so again...
These are the ones we have to worry about!
Dormant = sleeping...If it has not erupted for
years/ centuries..But gas still
escapes sometimes
Task: Complete the worksheet “how is a volcano formed?” using the following
missing words
Oceanic
Continental Crust
Erupts
Active
Constructive
Melt
Pushed down
Dormant
Conservative
Magma
Layers
Destructive
Earthquakes
Extinct
Mantle
Temperature
Ocean
Away
Collision
Formed
Atlantic
Gentle
Worksheet – how is a volcano formed? – ANSWERS (in order)
1. Constructive
2. Destructive
3. Conservative
4. Collision
5. Earthquakes
6. Oceanic
7. Pushed Down
8. Temperature
9. Melt
10. Magma
11. Continental Crust
12. Erupts
13. Layers
14. Formed
12. Away
13. Mantle
14. Ocean
15. Atlantic
16. Gentle
17. Extinct
18. Dormant
19. Active
How do you ‘grow’ a volcano?
Volcano erupts
Volcano builds up
Volcano formed
Plenary…
1 Krakatau, Indonesia
What is the area at the top of the volcano, shown in the pictures, called?
Kilauea, Hawaii
What is this substance?
Clue: it flows!
2
What type of plate boundary is this?
3
What is the name for this ‘ring’ of volcanoes?
4
Belknap, Oregon
Mauna Loa, Hawaii
What type of volcano are these?
5
Mt St Helens, USA
What type of volcanoes are these?
Mount Etna, Italy
6
Iceland
Do you think this volcano is at a constructive or destructive plate boundary?
7
Pinatubo, 1991
What is the cloud coming out of the top of the volcano made of?
8
9 Edinburgh Castle, Scotland
What would you call a volcano such as this?