1. Volcanoes

2. They result from plate tectonics
Volcanoes
They result from plate tectonics
The movement of plates or plate shifting
Vents- openings in the Earth’s crust; magma exits

3. 3 things they release
Molten rock (magma)
When it reaches the Earth’s surface it is called lava
Ash
Poisonous gases

4. Shield Volcano Composite Volcano Cinder Cone Volcano
3 types of Volcanoes
Shield Volcano
Composite Volcano
Cinder Cone Volcano
Depends on the type of eruption

5. Eruptions can happen several times
Shield Volcanoes
Largest volcanoes
Mild eruptions
Eruptions can happen several times

6. Shield Volcanoes magma
Rich in iron
Very fluid
Can flow a great distance
Produce gently sloping mountains

7. Where are they found?
Hawaii
Mauna Loa

8. Shield Volcanoes

9. Composite Volcanoes
Made of alternating layers of:
Ash
Cinders
Lava

10. Composite Volcanoes
More violent eruptions

11. Composite Volcanoes Magma
Rich in Silicates
Thicker lava
Gases are trapped in magma

12. Composite Volcanoes
Because of gases
This causes eruptions that alternated between flow and explosive activity
Steeper slopes
1000’s of meter high

13. Examples
Mount St. Helen
Mount Fuji

14. Smallest & most abundant Violent eruptions Gases are trapped in magma
Cinder Cone Volcanoes
Smallest & most abundant
Violent eruptions
Gases are trapped in magma
Larger amounts of gases

15. Hot ash and lava are thrown from the vent forming a cone.
Cinder Cone Volcanoes
Hot ash and lava are thrown from the vent forming a cone.

16. They are only active for a short period of time.
Cinder Cone
They are only active for a short period of time.

17. Cinder Cone

18. They are called seamounts Similar to Shield volcanoes
Can occur under water
They are called seamounts
Similar to Shield volcanoes

19. Converging Boundaries
Volcanoes occur at convergent Boundaries.
Usually around the Pacific Ocean
Ring of fire – 75% of all volcanoes are located on the Pacific Plate Boundary.

20. Convergent
As ocean plates subduct:
Magma rises and forms volcanoes

21. Divergent Boundaries Volcanoes can occur at divergent boundaries also.
When plates move apart:
Magma rises and fills in gaps
Magma creates a volcanic mountain

22. Hot Spots Magma from deep inside the mantle rises to the surface
This happens in the middle of plates
This is called a hot spot
This can form Islands

23. Chain of Islands Plates can move Hot Spots do not move
This is how chains of islands are formed
Hawaiian Islands