1. VOLCANOES

2. Volcano Basics
Active – a volcano that has erupted recently (geologically speaking)
Dormant – (sleeping) has erupted within the past few thousand years – will likely erupt again
Extinct – hasn’t erupted in 10’s of thousands of years; unlikely to erupt again

3. Mt. Rainier - active

4. Mount Baker - dormant

5. Shiprock Peak – extinct volcano

6. magma: molten rock inside the Earth lava: magma that has emerged on the Earth’s surface

7. er
lava
                              
magma

8. What makes a Volcano Violent?

9. viscosity: a fluid’s resistance to flow high viscosity = high resistance to flow (THICK) Low viscosity = low resistance to flow (THIN)
Nope…not movin’

10. You’re as slow as MOLASSES!!

11. Low viscosity magmas allow gases to escape easily and move easily through cracks.
In higher viscosity lavas, gas pressures build up and erupt explosively.
VIRTUAL LAB!!

12. Viscosity is determined by silica content and temperature.

13. The higher the silica content, the higher the viscosity.
The hotter the magma, the less viscous it is.

14. 1. Shield 2. Composite 3. Cinder cones
TYPES OF VOLCANOES
1. Shield
2. Composite
3. Cinder cones

15. Shield Volcanoes
- largest volcanoes (tallest when measured from the ocean floor)
- shaped like a gentle arch or shield
basaltic lavas (low silica content)

17. - usually non-explosive eruptions - results in lava flows - found in Hawaii (Mt. Kilauea) and Iceland

19. lava tubes: caves left behind after lava flows

21. Composite Volcanoes - coned shaped; sometimes called stratovolcanoes
- lava contains mostly andesite or rhyolite (higher silica content)
- more viscous

22. Combination of explosive activity (pyroclastic) and lava flows Responsible for most deaths of any type of volcano ex. Mount Saint Helens Mt. Pinatubo Mt. Fuji Mt. Vesuvius

23. Mount Saint Helens, Washington State

25. Mt. Saint Helens, after eruption

26. Mount Pinatubo, 1994

27. Mount Fuji, Japan
                                                    

28. Mount Vesuvius / Ruins of Pompei

30. Cinder Cones
- smaller volcanoes
- form quickly
are active for a few years and then usually go dormant

31. Wizard Island
                                                    

32. ex. Paracutin, Mexico - 1943, hole in ground
- 2 weeks prior, small tremors
- 1st day grew 10 m
- By 5th day it was 100 m tall
- After 2 yrs, it was 400 m tall
- went quiet after 9 years

35. Where are volcanoes?

36. Ring of Fire Area of the world where volcanoes are common
Outlines the Pacific Ocean

38. hot spot: area of volcanic activity independent of lithospheric plates ex. Hawaii

41. Features of Volcanoes
crater - depression found at the top of a volcano; formed by the explosion of the upper portion of the cone

42. hot springs: water is heated by the hot rock and reaches Earth’s surface
geyser: heating and circulation of water forms a pattern (RARE!)
ex. Old Faithful

43. Half of the 1,000 geysers in the world are in Yellowstone National Park, WY (United States)
                                

44. caldera: a giant crater that can be more than 12.5 miles in diameter
formed by rare, very violent eruptions
none have occurred in recorded history (they are 1000 times more violent than Mt. St. Helens!)
- Yellowstone caldera was formed 600,000 years ago!

45. Crater Lake, OR

46. Long Valley, CA

47. Aniakchak, AK
                                                    

48. Primary Effects Secondary Effects
Volcanic Hazards
Primary Effects
Secondary Effects

49. Lava flows: eruption of magma at Earth’s surface
Lava flows vary based on the composition of the magma.

56. tephra: any material that is blown out of a volcano (mostly ash)
Pyroclastic Activity: explosive volcanism where tephra is physically blown into the atmosphere
tephra: any material that is blown out of a volcano (mostly ash)

59. ash fall: huge quantities of rock, glass and gas are blown high into the air
- kills vegetation
- contaminate water
- structural damage
- jet engine “flame out”
- respiratory irritation

61. lateral blast: explosions of gas and ash from the side of the volcano; destroys part of the mountain ex. Mt. St. Helens

63. Poisonous Gases
- CO2, carbon monoxide, sulfur dioxide, and hydrogen sulfide
- can cause acid rain; contaminates water supply and vegetation

65. Secondary Effects lahar: debris flows and mudflows
volcanic debris becomes saturated with water
ex. Mt. Pinatubo, Philippines

67. Buildings buried after lahars at Pinatubo

68. Aerial View, Pinatubo Aftermath

69. Predicting Volcanoes
1. Monitoring of Seismic Activity- often the earliest sign
2. Thermal monitoring - measuring ground temperatures

71. 3. Topographic Monitoring - mountain may tilt and swell before an eruption 4. Volcanic Gas Emissions - changes in composition of gases may indicates rising of magma

72. 5. Geologic History - geologists map and date rocks around the area