2. Volcano : opening erupt an opening in the earth’s surface through which lava, hot gases, and rock fragments erupt

3. Magma 50-100 miles below the earth’s surface slowly begins to rise to the surface As the magma rises it melts gaps in the surrounding rock As more magma rises a large reservoir forms as close as 2 miles below the surface (magma chamber) Origin of Volcanoes

4. Pressure from the surrounding rock causes the magma to blast or melt a conduit (channel) to the surface where magma erupts onto the surface through a vent (opening) Origin of Volcanoes

5. The magma, now called lava, builds up at the vent forming a volcano Origin of Volcanoes

6. Often the volcano sides will be higher than the vent forming a depression called a crater Origin of Volcanoes

7. Crater :

8. Caldera: an unusually large crater or the remains when the cone collapses into its own magma chamber

9. The Birth of a volcano

10. Anatomy of a Volcano Cone : the above ground structure built from lava and/or tephra

11. Conduit : the path that magma takes from the magma chamber to the vent

12. Magma Chamber : the reservoir located under the volcano where magma collects and becomes the supply of magma/lava to build the volcano

13. Lava: liquid molten, liquid rock on the surface of the earth

14. Parasitic Cone:  a smaller secondary volcano built on the side of or near the main volcano, but sharing the same conduit to the magma chamber

15. Fumarole: a secondary vent that emits only gases

16. Fissure : crack a long fissure (crack) from which lava flows

17. Vent : opening of the volcano, through which lava, ash and gases flow

18. Take a minute to label the parts on the diagram (not all parts are shown)

19. Magma chamber conduit mantle Parasitic Cone Ash Cloud/Gases Vent Lava Flow Crater

20. Lava— There are 3 kinds:

21. Pahoehoe lava:  Hot, thin, fast flowing  harden with a relatively smooth surface  Often has a ropy or wrinkled appearance

22. Pahoehoe lava:

23. Aa lava: Cooler, thicker, slow moving Hardens with a rough, jagged, sharp edge surface

24. Pillow Lava:  Lava suddenly cooled by water  shows sack-like segments (stuffed pillows)

25. lava Can you identify the kinds of lava from the pictures? Circle your choice.

30. Tephra (pyroclastic, rock fragments) Volcanic Dust : Smallest particles and carried by atmosphere circulation

31. Volcanic Ash:  0.25-0.5 cm diameter  Generally settles out within miles of the cone but can be carried greater distances by stronger winds.  Forms a mudflow when mixed with water

32. Bomb :  Smaller bombs (gravel, pea size) are called cinders.  Walnut size bombs are called lapilli.  Larger fragments up to 4+ feet in diameter are called bombs.

33. Lahar (mudflow):  mixture of ash, eroded land, and water flowing down river valleys

34. Lahar (mudflow):

35. Gases : water vapor, carbon dioxide, nitrogen, sulfur dioxide, hydrogen sulfide, chlorine

36. Divergent Boundaries:  As the plate move long cracks (rifts) form and lava builds up forming volcanoes. Locations of Volcanoes

37.  If the boundary is on the ocean floor, volcanoes can grow tall enough to break the surface of the ocean and become islands (Iceland)

38. Convergent Boundaries:  Places where plates are moving toward each other forming a subduction zone.  One plate melts under the other and the magma moves upward to form volcanoes.

39.  Example: Pacific Ring of Fire

40.  Example: Cascade Volcanoes

41. Subduction & Magma Chambers

42.  Magma that may originate in the mantle or outer core will move upward, breaking the surface and forming a volcano, they are independent of plate boundaries and a chain of volcanoes may form as the plate moves across a hot spot. Hot Spots

43.  (Examples: Hawaiian Islands and Yellowstone National Park) Hot Spots

44. Formation of Hawaiian Islands

45. Two factors determine the type of eruption :  Amount of water vapor & other gases in the magma  The chemical composition of the magma Types of Volcanic Eruptions

46.  Trapped gases under high pressure will violently explode when the magma reaches the lower pressure of the surface.  Has granitic magma is very thick and plugs the vent causing the pressure to build until it blows violently out the vent  The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions Explosive Eruptions

47. Mt. St. Helens Mont serrat Mt. Pinatubo

48. The eruption of Mt. st. Helens in 1980

49.  Low pressure gas  Has basaltic magma (is more fluid and will flow instead of explode)  And has low water content Quiet Eruptions

50. A typical Hawaiian Eruption

51. Soda Bottle Volcano Demo 1.Roll up the tissue with the baking soda into a little packet 2.Push the tissue into the bottle 3.Replace the lid of the bottle 4.Observe! What do you notice? Wait a minute or so… 5.Shake the bottle for about 10 seconds 6.Be sure the bottle is in the bin and back up a little 7.Remove the cap from the bottle. 8.What happens?

52. Cinder Cones :  Small base, steep-sided, loosely consolidated  Up to 1000 feet tall  Life span of a few years  Commonly built from gravel size lava rock fragments call cinders  Has violent eruptions, dangerous when close. Types of Volcano Mountains

54. Cinder Cones : Types of Volcano Mountains Cinder Cones

55. High pressure gas bubbles causes thick lava to explode into the air, lava begins to cool as it rises and falls becoming very sticky When lava hits the ground it sticks rather than flows This builds a steep cone with a small base

56. Sketch a Cinder Cone Volcano:

57. Types of Volcano Mountains Shield Volcanoes:  Large base, gentle slope, lava rock layers  A few miles high  Life span of a million years or more  The lava is hot, thin, very fluid, often basaltic.  Example : Hawaiian Islands

58. Shield volcano on Mars; Taken from space Take a look at these examples: http://www.volcano.si.edu/world/tpgallery.cfm?category=Shield%20Volcanoes The Mauna Loa volcano in Hawaii— the largest volcano on Earth—has the broad expanse characteristic of shield volcanoes. It spreads across half the island of Hawaii.

59. Shield Volcanoes Mauna Kea Shield volcanoes

60. Sketch a sheild Volcano:

61. Composite (strato) Volcanoes:  Large mountain volcano often snow capped, a few miles high  Life span of million years or more  Have alternating eruptions of tephra (air- borne) and lava. The tephra adds height to the volcano and the lava cements the tephra together and adds to the base.  Found mostly in subduction zones and have violent eruptions. Examples : Mt Rainier, Mt Fuji, Mt Kilimanjaro Types of Volcano Mountains

62. Composite (strato) Volcanoes: Mt. Rainier Mt. Fuji Mt. Kilimanjaro

63. Sketch a composite Volcano:

64. Composite/strato volcanoes

65. Types of volcanoes

66. Active (awake):  Has erupted within recent time and can erupt again at any time. Pre-eruption activities :  Increase in earthquake activity under the cone  increase in temperature of cone,  melting of ice/snow in the crater  swelling of the cone  steam eruptions  minor ash eruptions Volcano Activity Levels (Stages)

67. Mt St. Helens

68. Dormant (sleeping):  No eruption within recent times, but there is record of past eruptions  Can become active and erupt again after a “wake up” period  Example  Example: Mt. Rainier

69. Extinct:  No eruption within recorded history  Not expected to ever erupt again Example: Mount Mazama (Crater Lake)

70. Crater Lake

71. Mount Rainier dangerousThe most dangerous volcano in the US laharsThe danger is mostly from lahars traveling down river valleys at a speed of 25mph and destroying everything in its path 100,000 people live on the solidified mudflows of previous eruptions

72. Mount Rainier unstableThe mountain is dangerously unstable, a tall, steep heap of loose rock held together by the force of gravity and a cubic mile of glacier ice that could be melted or shaken loose 500 yearsLahar flows average every 500 years and have gone as far as the Puget Sound lowlands (1 in 7 chance of it happening during your lifetime) 4 timesMount Rainier has erupted 4 times in the last 4000 years with the last eruption 200 years ago

74. V ideo C lips Volcano by brainpop