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?