1. Volcanoes

2. Sweet Volcano Music Video!

3. What is a Volcano? The term volcano has two main definitions:
The opening in Earth’s crust through which molten rock, gases, and ash erupt
The landform that develops around this opening.

4. Volcanoes
Why volcanoes erupt paper!

5. BOOM!

7. Volcanoes In order for a volcano to form we need magma to form.
The following three conditions allow magma to form:
A decrease in pressure can lower the melting temperatures of materials in the asthenosphere. (divergent plate boundaries)
An increase in temperature can cause materials in the asthenosphere to melt. (hot spots)
An increase in the amount of water in the asthenosphere can lower the melting temperatures of materials there. (subduction zones)

8. Divergent Plate Boundaries
Remember that divergent plate boundaries occur where two plates are moving away from one another.
As the plates move away the lithosphere is being thinned and the pressure on the asthenosphere is being released.
This causes a rift to form where magma that is circulating through the mantle due to convection can rise to the surface and form volcanoes.

9. Divergent Plate Boundaries

10. Subduction Zones
Subduction zones occur at convergent plate boundaries when one plate goes underneath the other as they collide.
Two types of convergent zones result in subduction:
Continental-oceanic
Oceanic-oceanic

11. Continental-Oceanic Convergence

12. Oceanic-Oceanic Convergence

13. Hot Spots
Hot spots are areas of volcanic activity that result from plumes of hot solid material that have risen from deep within Earth’s mantle.
Hot spots remain in the same place as the lithospheric plates move across them.
The Hawaiian Islands formed as the pacific plate moves over a hot spot.

14. Hot Spots

15. Meet Loihi
18,000 years away from a new island!

16. Another Hot Spot

17. Where do they occur?
Now that you know a little bit of background information on volcanoes lets see where they commonly occur.