Volcanism

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Volcanism

  1. 1. VOLCANISM The Walker School Geology
  2. 2. Volcanism is a Constructive Process  Atmosphere  Water  Crust Painting of Early Earth’s Volcanism
  3. 3. Current Volcanism  Iceland  Hawaiian Islands  Azores  Galapagos Islands Volcanism at Hawaii’s National Park
  4. 4. Notable Volcanic Eruptions Table 5-1, p. 135
  5. 5. Mount Vesuvius Continues to Errupt Fig. 5-1, p. 134
  6. 6. Maps of the World’s Major Volcanoes •550 Are Currently Active •About 1 dozen are erupting at anyone time •Responsible for extrusive igneous rock
  7. 7. Viewing Volcanoes in Google Earth
  8. 8. Basic Volcanic Structure
  9. 9. Pyroclastic Materials  Blocks  Bombs  Lapilli  Ash Size Volcanic Bomb
  10. 10. Lava Tubes at Volcanic National Park, HI Lava Tube in Hawaii Fig. 5-3a, p. 137
  11. 11. Lava Textures Pahoehoe (pah-hoy-hoy) is Aa (ah-ah) is characterized by a characterized by its smooth and rough, clinkery surface and is often ropey or wrinkly surface and what most viscous and hot lava is generally formed from more flows look like. fluid lava flows. Fig. 5-4a, p. 137
  12. 12. Lava Composition  Felsic Lava: high percentage (>63%) of silica, and trapped gasses; highest viscosity, lowest temperatures  Andesitic Lava: (52-63%) of silica  Mafic Lava: (45-52%) of silica + high percentage of Magnesium (Mg); typically occur at subduction zones  Balsitic Lava: (45-52%) of silica + high percentage of Iron (Fe); typically occur at oceanic divergent pages  Ultramafic Lava: (=<45%) of silica; lowest vicsosity, highest temperatures
  13. 13. Columnar Jointing at Devil’s Post Pile National Monument, CA Fig. 5-5b, p. 138
  14. 14. Inversion of Topography  1. Lava flows into the valley  2. Lava cools and crystallizes, forming extrusive igneous rocks.  3. Areas adjacent to the flow erode more easily then the flow  4. Over time, an inversion is produced. Fig. 5-6ab, p. 139
  15. 15. Craters of the Moon National Monument, ID http://www.nps.gov/crmo/ Fig. 5-3b, p. 137
  16. 16. VOLCANIC TYPES
  17. 17. Types of Volcanoes
  18. 18. Fig. 5-18, p. 149
  19. 19. Plutonic Bodies
  20. 20. Formation of a Caldera Fig. 5-9a-d, p. 142
  21. 21. Crater Lake, OR Caldera Caldera Floor of Crater Lake Wizard Island, Crater Lake, OR
  22. 22. Shield Volcanos Fig. 5-10a, p. 143
  23. 23. Shield Volcano, Mauna Loa, HI •Low Viscosity Basalt Flows •Lava fountains •Most common in ocean basins
  24. 24. Cinder Cones Fig. 5-11a, p. 144
  25. 25. Cinder Cones, Mojave Desert, CA •Eruptions are short-lived. •Large, bowl-shaped craters. •Ash builds up rapidly. •Few lava flows. •Lava flows typically from base of cone.
  26. 26. Stratovolcanoes (Composite Cones) Fig. 5-13a, p. 146
  27. 27. Stratovolcano, Mt. Rainier, WA From Space •Composed of layered sills. •Lahars, or volcanic mud flows are common. •Have steep slops near summit. •Lava flows from andesite.
  28. 28. Lahar Flows, Mt. Pinatubo, Philippines Mt. Pinatubo from Space Fig. 5-14a, p. 146
  29. 29. Lava Domes Fig. 5-15b, p. 147
  30. 30. Lava Dome, Mt. St. Helens, WA •Composed of felsic magma. •Formed from intermediate magma forced up under great pressure. •Highly unstable, will collapse under weight of rock. Fig. 5-15a, p. 147
  31. 31. Mt. Saint Helens Eruption http://www.youtube.com/watch?v=bgRnVhbfIKQ
  32. 32. VOLCANIC ERUPTIONS
  33. 33. Types of Erruptions
  34. 34. Fig. 5-17, p. 148
  35. 35. Fissure Eruptions  Generated along a linear fracture  Composed of low- viscosity melt  Commonly occur along divergent plate boundaries  Also common on the edges of large Fissure eruption in Iceland volcanoes.  Produces a curtain of fire.
  36. 36. Columbia River Basalt Plateau Fig. 5-19, p. 150
  37. 37. Volcanic Explosive Index
  38. 38. Primary Effects of Volcanoes  Pyroclastic Flows  Fumaroles  Landslides  Ash Fall  Earthquakes  High Temperatures
  39. 39. Secondary Effects of Explosions  Suffocation from Ash  Asphyxiation from Volcanic Gasses  Tsunamis  Temperatures Decreases
  40. 40. Environmental Effects  Involved in the formation of continental crust and offset weathering and erosion  Provide nutrient rich soils  By trapping clouds at their peaks, water for agriculture  Agriculture based cultures are attracted to their bases
  41. 41. Volcanic Gasses  Water Vapor  Carbon Dioxide  Nitrogen  Sulfur Dioxide  Hydrogen Sulfide  Carbon Monoxide  Hydrogen  Chlorine Gasses emitted from fumaroles at the Sulfur Works in Lassen Volcanic National Park, CA Fig. 5-2, p. 136
  42. 42. Effects of Volcanoes on Climate  Nucleation, condensation, and sedimentation of aerosols (acid rain)  Change in Albedo from ash cloud  Tropospheric cooling from the addition of sulfur to the stratsophere  Ozone destruction through the formation of atomic chlorine
  43. 43. SUPER ERUPTIONS
  44. 44. Supereruptions http://www.pbs.org/wgbh/nova/megavolcano/about.html
  45. 45. Discovery Questions  What does it take to be classified as a super eruption?  When did the last one occur? Why is their controversy about the date?  What would be the primary effects of such an eruption?  For those who survived the initial eruption, what would happen in the following months, or years?  How did the Toba explosion effect the evolution of humans?
  46. 46. DISTRIBUTION & MONITORING
  47. 47. Distribution of Volcanoes  Circum-Pacific Belt (60%)  Mediterranean Belt (20%)  Mid-Oceanic Ridges (20%)  More common along both divergent than convergent plate boundaries.  Mainly composed of intrusive magma flows.  Composed of mafic magma that forms beneath spreading plates.  Pyroclastic materials are not common because lava is fluid.  Water pressure prevents gasses from expanding and escaping. Fig. 5-20, p. 151
  48. 48. USGS Volcano Hazards Program http://volcanoes.usgs.gov/
  49. 49. Alaska’s Volcano Observatory http://www.avo.alaska.edu/
  50. 50. Alaska’s Volcanoes
  51. 51. Cascade Volcano Observatory http://vulcan.wr.usgs.gov/
  52. 52. The Cascade Range
  53. 53. Lassen Peak, CA  Largest Lava Dome in the World
  54. 54. Lassen Peak Diagram Concept Art, p. 154
  55. 55. Mid-Atlantic Ridge & Iceland
  56. 56. Formation of Surtsey Island, Iceland http://www.youtube.com/watch?v=4MmX_i7S9u4
  57. 57. Important Monitoring Techniques Fig. 5-23, p. 159
  58. 58. Fumarole Gas Monitoring  Chemically-selective sensors for SO2 and CO2 measure gas concentrations and a wind sensor measures wind speed and direction.  Data from solar-powered stations are transmitted to GOES geostationary satellite and then down to observatories every 10 minutes, providing near real time data on degassing of volcanoes
  59. 59. Ground Deformation Monitoring  Paint  Electronic Distance Meters  determine the horizontal movements that occur on active volcanoes  Tiltmeters  leveling surveys to measure vertical motions  Global Positioning Systems  allows us to measure horizontal motions much more accurately and conveniently, and also to estimate vertical motions in the same survey
  60. 60. Remote Sensing  The Advanced Very High Resolution Radiometer (AVHRR) is a space-borne sensor embarked on the NOAA family of polar orbiting platforms.  The primary purpose of these instruments is to monitor clouds and to measure the thermal emission (cooling) of the Earth.  The main difficulty associated with these investigations is to properly deal with the many limitations of these instruments, especially in the early period (sensor calibration, orbital drift, limited spectral and directional sampling, etc).
  61. 61. WHAT ARE BLACK SMOKERS?
  62. 62. Hydrothermal Vents  Distributes heat and drives water circulation in the ocean through convection  Provides energy source in the form of hydrogen sulfide to benthic chemotrophs  Distributes minerals and influences the composition of the ocean
  63. 63. Hydrothermal Plume White Black smoker smoker Sulfide deposit Tube worms Magma White clam White crab
  64. 64. Location of Major Vent Systems
  65. 65. Learn More About Vents http://www.divediscover.whoi.edu/vents/index.html
  66. 66. Hydrothermal Vent Chemistry

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