1. What Are Volcanoes?
Volcanoes are openings (vents) in the ground where magma (molten rock) from deep in side the earth forces its way to the surface. The magma may appear as flows of molten lava; volcanic bombs; or ash and dust
Steam, gas and dust
Crater
Falling Ash and Volcanic Bombs
Secondary Cone
Layers of ash and lava from previous eruptions
Lava Flow
Main Vent
Magma Chamber

2. WHITEBOARD: FASTEST FINGERS ON THE BUZZER!!!
Which is the largest volcano in the world?

3. The largest volcano in the world is Mauna Loa in Hawaii
The largest volcano in the world is Mauna Loa in Hawaii. Its whole volume is about 80,000 cubic kms. It is a shield volcano.

4. Recent Volcanic activity in the news…

6. H/W TASK 1
Describe and explain the global distribution of volcanic activity .
Which areas are of particularly high risk from volcanoes? ( 6 marks)
Tips
Which areas of the world have the majority of volcanoes?
Locate specific named examples
Why is this? Think about plate boundaries. Are they always ON plate boundaries?
In your answer please refer to the phrase ‘ areas of high volcano risk’
Ref: Using the previous map and/ or Fig 1.2 Hodder P.3

7. The Tectonic setting of Volcanoes
A. Island Arcs - Alaska, Japan and Indonesia
B. Hot Spots – Hawaiian Islands, Canary Islands
C. Ocean Ridges – Iceland
D. Continental Margins – Rockies/Andes of the Americas
E. Continental Rifts – East African Rift Valley

8. What Happens At Plate Boundaries To Create Volcanoes?
The majority of volcanoes are found at plate boundaries (where 2 or more plates meet). There are 3 different types of plate movement that cause volcanoes: -
1) Plates Move Apart
2) Plates Move Together
3) Hotspots (anomalies- see next lesson

9. Web geology animations
( see volcanoes and vulcanism- the occurrence of volcanoes)

10. Constructive (DIVERGENT)
Plates move apart
Usually under ocean
Cracks and fractures form where no solid crust.
Magma forces its way up to the surface to form a VOLCANO

11. Iceland: An example of continental rifting where volcanoes form
Iceland has a divergent plate boundary running through its middle
Iceland is located right on top of a divergent boundary. In fact, the island exists because of this feature.
As the North American and Eurasian plates were pulled apart (see map) volcanic activity occurred along the cracks and fissures (see photographs).
With many eruptions over time the island grew out of the sea!
Question: Why don’t we have islands like Iceland where ever we get an Ocean Ridge?
Answer: Scientists believe that there is a large mantle plume (an upwelling of hot mantle material) located right underneath where Iceland has formed. This would mean that more material would be erupted in the Iceland area compared with if there was just the divergent boundary without the plume underneath it.

12. Volcano Eyjafjallajökull :ICELAND
Volcano Eyjafjallajökull (AY-yah-fyah-lah-YOH-kuul) has only erupted three times since the Vikings settled the island in the 9th century (1200 years ago..)
The last eruption was in 1820 but after being dormant for nearly 200 years, the volcano began erupting in late March 2010

13. How are volcanoes formed at constructive/divergent plate boundaries?
Basic lava/shield volcanoes:
Formed at constructive plate boundaries where two plates are moving away from each other. Magma rises up to fill the gap and gentle volcanoes form as a result e.g. Mauna Loa, Hawaii

14. Continental Rift System Volcanoes
Examples: Kilimanjaro and Ol Doinyo Lengai (Tanzania), Nyiragongo (Congo), Erta Ale (Ethiopia) in the East African Rift system

15. E.G:‘Erte Ale’ volcano , Ethiopia( with a permanent lava lake in the crater)
See Ian Stewart absailing down to the crater in ‘Power of the Planet-Volcano!’