1. Volcano Types and Formation

2. Shield Volcano Typically occur at divergent boundaries and hot spots.
Molten rock pushes its way up to the surface as the plates spread.
Oceanic crust passes over a hot spot in the mantle.
Very large in scale.
Erupt in gentle lava flows ( mainly basaltic lava)

3. Formation over a hot spot.

4. Haleakala, HI

5. Mauna Loa, HI

6. Cinder Cone Usually Small in scale.
Formed from cinders piling up on itself.
Typically felsic lava.

8. Pyroclastic Layers

9. Pyroclasts Rock fragments from a volcanic eruption. Smallest = Ash
Medium = Cinder
Largest = Bombs
Which is the most deadly?

10. Composite Volcanoes Contain granite lavas that are very viscous.
These lavas can trap gas and act as “plugs” in the vent of a volcano.
Pressure builds up and can cause explosive eruptions.
Formed from alternating layers of lava flows and pyroclastic eruptions.
Mixture of felsic and basaltic lava.
Continent-Oceanic convergent boundaries

11. Dissected Stratovolcano

12. Mt. Hood, Washington

13. Mt. Egmont, New Zealand

14. Calderas
Formed from the largest and most explosive volcanic eruptions.
Extremely large volumes of magma are removed from below the ground.
The empty chamber then collapses.

15. Crater Lake, Oregon

16. Yellowstone National Park, WY