1. Volcanoes

2. volcano: place where magma reaches the surface

3. magma: liquid, molten rock underground
lava: magma that reaches the surface
lost gas, gained rock

4. MID-OCEAN RIDGE: occurs where plates are moving apart
lava flows out smoothly and fluidly from cracks

5. SUBDUCTION ZONE: occurs at subduction boundaries
usually explosive and erupted material is mostly lava

7. HOT SPOTS: areas of volcanic activity in lithospheric plates

8. Hawaiian Islands are an example

12. - Temperature - Composition
• Viscosity: the measure of a material's resistance to flow (Ex: water is thin, so it has a low viscosity)
• Factors affecting viscosity of lava:
- Temperature
- Composition

13. two types of lava:
felsic: much silica, light-colored, slow moving (continental crust)

14. mafic: low silica, dark-colored, fast moving (oceanic crust)

15. Aa Lava
Pahoehoe
Lava

16. Pahoehoe

17. Aa

18. Aa

19. Pillow lava from Hawaii
Click me!

21. many magmas contain dissolved gases that are given off
water vapor, carbon dioxide (CO2), sulfur (S)
magmas with more gases have more explosive eruptions

22. tephra: solid fragments ejected from a volcano
ash (fine, glassy fragments)
lapilli (walnut sized particles)
blocks (hardened lava)
bombs (ejected as hot lava)
Sometimes called pyroclastic material

23. • Composition of the magma • Temperature of the magma
 Factors that determine the violence of an eruption:
• Composition of the magma
• Temperature of the magma
• Dissolved gases in the magma

24. Examine video clips of erupted materials.

31. Other Volcanic Hazards
1) Ash in the atmosphere can disrupt air travel and, in severe instances, affect climate.
Mount Pinatubo, Philippines - Plane on its tail because of weight of ash in 1991
Lascar (northern Chile) erupted in Eruptions such as this can send large amounts of fine ash particles high into the atmosphere, where they sometimes remain for years. The ash particles scatter incoming sunlight, shading and slightly cooling Earth's surface. Some very large eruptions can have a measurable effect on climate worldwide.

32. http://www. livescience. com/31127-iceland-volcano-ash-plume-trouble

33. Other Volcanic Hazards
2) Lahars - Mudflows made up of volcanic debris. They flow like liquids, but because they contain suspended material, have a consistency similar to wet concrete. Lahars can travel at speeds of over 50 mph and reach distances dozens of miles from their source.

35. Other Volcanic Hazards
3) Volcanic Gases - Most of the gas released in an eruption is harmless water vapor (H2O), but volcanoes also produce carbon dioxide, sulfur dioxide, hydrogen sulfide, fluorine gas, and other gases. All of these can be deadly.
Lake Nyos, Cameroon – ,700 people and 3,500 livestock died when suffocated by CO2 from the lake bottom.

37. composed of quiet lava flows
Shield Volcano
composed of quiet lava flows
form gently sloping, dome- shaped mountain
basaltic (mafic) magma

39. largest = Mauna Loa in Hawaii

40. Made mostly of pyroclastic material Formed from explosive eruptions
Cinder Cone Volcano
Made mostly of pyroclastic material
Formed from explosive eruptions
Not very high, narrow base, steep sides
Granitic (felsic) magma

44. built up of alternating layers of rock and lava
Composite Volcano
(Stratovolcano)
built up of alternating layers of rock and lava
explosive eruptions at first with tephra, then quiet with lava
forms large, cone-shaped mountains
made of felsic and mafic magma

45. Mount Rainier (left) and Mount Hood (right)

47. Mount Fuji