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Volcanoes Chapter 4 Part 2 Volcanic gases

Volcanoes Chapter 4 Part 2 Volcanic gases Up to 9% of composition Water vapor [can be 50 – 80%] A primary source of original oceans (also comets) Carbon dioxide Sulfur dioxide Hydrogen sulfide Lesser gases HCl, HF, Cl Form vesicles when trapped in lava

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Volcanoes Chapter 4 Part 2 Volcanic gases

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  1. Volcanoes Chapter 4 Part 2Volcanic gases • Up to 9% of composition • Water vapor [can be 50 – 80%] • A primary source of original oceans (also comets) • Carbon dioxide • Sulfur dioxide • Hydrogen sulfide • Lesser gases • HCl, HF, Cl • Form vesicles when trapped in lava

  2. Mount Unzen, Japanone of 75 active volcanoes in Japan On island of Kyushu 1991 eruption – ash flows at 200 km per hr; 1792 eruption killed 15,000

  3. Lake Nyos, Cameroon, Africa1986 event Landslide and convective overturn of lake water released CO2 3000 cattle and 1700 people died

  4. Gas and steam as lava hits ocean water

  5. Mt Pinatubo 1991 Aerosols, extra fine particles, remained in atmosphere for one year

  6. Fig. 7.08 Stephen Marshak

  7. Fig. 7.10 Scoria cones are hills of basalt and andesite pyroclastic material produced by a single eruption

  8. Paricutin Volcano, Mexico 1943

  9. also much wider than high Shield volcano – note low angles on flanks Fig. 7.12a W. W. Norton

  10. Fig. 7.13 W. W. Norton

  11. Calderas large volcanic craters Examples include Crater Lake, OR; Yellowstone NP, WY; Jemez caldera, NM

  12. Which type of structure is this? What characteristics tell you it is that particular structure?

  13. W. W. Norton Worldwide volcanism

  14. Central point vs. fissure eruptions Fig. 7.09ab W. W. Norton

  15. Flood basalts • Low viscosity covering immense areas • Large volume of basalt • Siberia – 3 million cu km about 250 My ago • Major effect on life at the time • Deccan plateau [India] – 1.5 million cu km about 65 My ago • Added to meteorite impact, this caused problems! • Columbia River [Pacific NW] – 1.2 million cu km about 10 My ago

  16. Fig. 7.18a W. W. Norton

  17. Columbia River basalt flows Photo by D Best

  18. Volcanic tuff deposits along I-40just west of Kingman, AZ Photo by D Best

  19. Volcanic hazards • Pyroclastic debris – flows, ash, pumice, lapilli • Blast – both vertical and lateral • Landslides • Lahars • Earthquakes and tsunami • Gas • Climatic changes due to particulates

  20. Tectonic action in the Pacific Northwest Subducting slab is only 8 my old Evidence of M 9 EQ in 1700 Top of Juan de Fuca plate and the N American continent are locked together—holding stress

  21. Mt Rainier, WA Potential major eruption or landslide Highest peak in Cascades Problems Great height Largest ice pack in lower 48 states Hot water spring system under surface Photo by D Best

  22. Mitigate the hazard • Forecasting an eruption by using • seismic data • thermal changes • surface tilting and swelling • volcanic gas emissions • past history

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