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  • 1. VOLCANISM The Walker School Geology
  • 2. Volcanism is a Constructive Process  Atmosphere  Water  Crust Painting of Early Earth’s Volcanism
  • 3. Current Volcanism  Iceland  Hawaiian Islands  Azores  Galapagos Islands Volcanism at Hawaii’s National Park
  • 4. Notable Volcanic Eruptions Table 5-1, p. 135
  • 5. Mount Vesuvius Continues to Errupt Fig. 5-1, p. 134
  • 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. Viewing Volcanoes in Google Earth
  • 8. Basic Volcanic Structure
  • 9. Pyroclastic Materials  Blocks  Bombs  Lapilli  Ash Size Volcanic Bomb
  • 10. Lava Tubes at Volcanic National Park, HI Lava Tube in Hawaii Fig. 5-3a, p. 137
  • 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. 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. Columnar Jointing at Devil’s Post Pile National Monument, CA Fig. 5-5b, p. 138
  • 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. Craters of the Moon National Monument, ID Fig. 5-3b, p. 137
  • 17. Types of Volcanoes
  • 18. Fig. 5-18, p. 149
  • 19. Plutonic Bodies
  • 20. Formation of a Caldera Fig. 5-9a-d, p. 142
  • 21. Crater Lake, OR Caldera Caldera Floor of Crater Lake Wizard Island, Crater Lake, OR
  • 22. Shield Volcanos Fig. 5-10a, p. 143
  • 23. Shield Volcano, Mauna Loa, HI •Low Viscosity Basalt Flows •Lava fountains •Most common in ocean basins
  • 24. Cinder Cones Fig. 5-11a, p. 144
  • 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. Stratovolcanoes (Composite Cones) Fig. 5-13a, p. 146
  • 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. Lahar Flows, Mt. Pinatubo, Philippines Mt. Pinatubo from Space Fig. 5-14a, p. 146
  • 29. Lava Domes Fig. 5-15b, p. 147
  • 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. Mt. Saint Helens Eruption
  • 33. Types of Erruptions
  • 34. Fig. 5-17, p. 148
  • 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. Columbia River Basalt Plateau Fig. 5-19, p. 150
  • 37. Volcanic Explosive Index
  • 38. Primary Effects of Volcanoes  Pyroclastic Flows  Fumaroles  Landslides  Ash Fall  Earthquakes  High Temperatures
  • 39. Secondary Effects of Explosions  Suffocation from Ash  Asphyxiation from Volcanic Gasses  Tsunamis  Temperatures Decreases
  • 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. 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. 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
  • 44. Supereruptions
  • 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?
  • 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. USGS Volcano Hazards Program
  • 49. Alaska’s Volcano Observatory
  • 50. Alaska’s Volcanoes
  • 51. Cascade Volcano Observatory
  • 52. The Cascade Range
  • 53. Lassen Peak, CA  Largest Lava Dome in the World
  • 54. Lassen Peak Diagram Concept Art, p. 154
  • 55. Mid-Atlantic Ridge & Iceland
  • 56. Formation of Surtsey Island, Iceland
  • 57. Important Monitoring Techniques Fig. 5-23, p. 159
  • 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. 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. 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).
  • 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. Hydrothermal Plume White Black smoker smoker Sulfide deposit Tube worms Magma White clam White crab
  • 64. Location of Major Vent Systems
  • 65. Learn More About Vents
  • 66. Hydrothermal Vent Chemistry