1. Volcanoes

2. Super Volcanoes

3. Eruptions of the Yellowstone volcanic system have included the two largest volcanic eruptions in North America in the past few million years; the third largest was at Long Valley in California and produced the Bishop ash bed. The biggest of the Yellowstone eruptions occurred 2.1 million years ago, depositing the Huckleberry Ridge ash bed. These eruptions left behind huge volcanic depressions called “calderas” and spread volcanic ash over large parts of North America (see map). If another large caldera-forming eruption were to occur at Yellowstone, its effects would be worldwide. Thick ash deposits would bury vast areas of the United States, and injection of huge volumes of volcanic gases into the atmosphere could drastically affect global climate. 

7. Volcanoes Opening in Earth’s surface 3 places
Forms mountain when layers of lava and volcanic ash erupt and build up.
3 places
Divergent plate boundaries
Convergent plate boundaries
Hot spots

8. Magma Viscosity - resistance of a liquid to flow
Molten rock beneath earths surface
Viscosity - resistance of a liquid to flow
Higher the viscosity the slower it flows
Ex. Oil 10 W 30, syrup
Lower the viscosity the faster it flows
Water, pop
Viscosity depends on the Silica content and the temperature
Silica is made up of oxygen and silicon

9. More silica higher its viscosity
Produces light colored lava
ex. rock rhyolite
Less silica lower the viscosity
Produces dark colored lava
ex. basalt

10. Lava Magma that reaches the surface. 2 types of Land Lava
1. Pahoehoe – fast moving, hot lava, low
viscosity
Smooth, hardens into ripples

11. 1. Aa Lava – cooler and slower moving Sharp/jagged surface

12. Pillow Lava
smooth lumps
occurs underwater

13. Types of Volcanoes 3 major types 2 factors Shield Cinder-cone
Composite
2 factors
type of material that forms the volcano
type of eruptions that occur
Types of Volcanoes (Video)

14. Shield Volcanoes
Mountain with broad, gently sloping sides and a nearly circular base.
Form when layer upon layer of lava accumulates during nonexplosive eruptions
Largest of all the types
The Hawaiian Islands

15. Sheild

16. Shield Volcano

17. Mauna Loa, Hawaii

18. Cinder-Cone Volcanoes
Material ejected high into the air falls back down to Earth and piles up around the vent
Steep sides
Generally small
most are less than 500 m.
Izalco volcano in El-Salvador

19. Cinder Cone

20. Izalco

21. Composite Volcanoes Layers of volcanic fragments alternate with lava
Larger than cinder-cone volcanoes
Mount Saint Helen and Mount Rainier
found in the northwestern U.S

22. Composite

23. Anatomy of a Volcano Vent Crater Conduit Magma chamber Dike Sill
Where magma becomes lava
Crater
Bowl shaped depression
Conduit
Runs from mantle to magma chamber
Magma chamber
Holds magma
Dike
Side shoot of magma flow that breaches surface
Sill
Side shoot of magma flow that does not breach surface

26. Pyroclastic flow – a flow of hot gas, ash, and rock that moves down the side of the volcano.
Flow down a slope at incredible speeds.
travel at speeds of nearly 200km/h
may contain hot, poisonous gases VIDEO

27. What determines the magnitude of the eruptions?
Quiet Eruptions – low in silica, flows easily
Ex. Hawaii
Explosive Eruptions – high in silica, thick and sticky.
Magma build up in the volcano’s pipe plugging it like a pipe.
Ex. Mt. St Helens
Before After

28. Tephra – air debris from a volcanic explosion
Ash
Lapilli
Bomb
Blocks

29. Calderas Large, crater shaped basin Formed by volcano top collapsing
Crater Lake, Oregon

30. Pyroclastic flow
15 seconds
30 seconds
40 seconds
60 seconds
5 minutes

31. Landforms from Volcanoes
Volcanic Neck

32. Dikes