1. Intro to Volcanoes

2. What is a Volcano
Volcano: a weak spot in the crust where molten rock (magma) comes to the surface
Most volcanoes are located around subduction zones and hot spots
Over 75% of worlds volcanoes are found th Pacific Rim (ring of fire)

3. How they form Volcanic eruptions occur when magma rises to the surface
Caused as the asthenosphere melts
A decrease in pressure (mid-ocean ridge or rift valley)
An increase in temperature (hot spot)
An increase in the amount of water in the asthenosphere (subduction zones)

4. Where Most volcanoes occur at Divergent boundaries
Convergent bounders that have subduction
Hot spots

5. Divergent Boundaries
A decrease in pressure allows magma to rise as plates pull apart from one another
These can often cause fissure volcanoes such as the Mid-Atlantic Ridge and the Great Rift Valley

6. Convergent Boundaries
Subduction increase the amount of water in the asthenosphere which lowers the melting temp
As the denser oceanic crust is pushed lower, it melts into magma
Volcanoes can form on land or under water to rise up and form islands

8. Hot spots
Volcanoes can also occur at places that are not plate boundaries These hot spots are areas where hot magma rises from deep in Earth’s mantle Magma escapes where the crust is the thinnest or weakest It starts out solid then it melts when it reaches areas of lower pressure

9. Example of Hot Spot
Volcanoes that make up Hawaii.

10. Volcano Anatomy

11. Four types Composite volcano (stratovolcano) Shield volcano
Cinder Cone
Fissure Volcanoes

12. Composite Volcano Also called a stratovolcano
Made of alternating layers of ash and lava
Steep slopes, tall
Explosive! Violent eruptions of thick lava and/ or ash and rock
Most commonly form from subduction zone
Examples: Mt. Shasta, Mt St. Helens, Pinatubo, Mt. Vesuvius

13. Mt. St. Helens, WA

14. Shield Volcano Large, broad volcanoes Gentle slopes
Made from frequent lava eruptions
Lave tends to be thin, runny
Most often form at a hot spot
Examples: Kilauea, and Mauna Loa in Hawaii

15. Mauna Loa, Hawaii

16. Cinder Cone Simplest type of volcano
Made of particles and chunks of lava, material ejected from vent
Small with bowl-shaped top
Often near other larger volcanoes
Example: cinder cones around Shasta, Cerro Negro in Nicaragua

17. Krakatau, Indonesia

18. Cinder Cones
Iceland

19. Fissure Volcanoes
Form in long cracks where plates are pulled apart and near other volcanoes where the crust is weakened
Typically near cinder cone or shield volcanoes

20. Fissure volcanoes

21. Yellowstone
Check out how large some of the lava flows were from the Yellowstone Volcano!!!

22. How does a Caldera Form? A) A Volcano’s pressure starts to build up
B) The Volcano releases large amounts of Lava
C) As the Lava is released, the pressure decreases and the volcanic mountain begins to collapse, forming a concave shape in the center of the volcano.
D) The center of the volcanic mountain may begin to fill with water and form a lake.

23. Crater Lake in Oregon State should actually be called Caldera Lake

24. So if that’s not cool
Volcanoes are also beginning to play a role in extreme sports activities
Volcano boarding is a real thing that you can go do
That’s right you can go on vacation and basically snow board/sled down ash
Just don’t fall

25. Label the parts of a volcano
Word Bank:
Main Vent/Crater
Secondary Vent
Magma Chamber
Lava
Ash & Dust Cloud
Tephra Bombs
Cone