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Volcanic Hazards p. 138-140, web reading

Volcanic Hazards p. 138-140, web reading. Volcano Facts Volcano Hazards Fall processes Flow processes Other types Predicting Volcanic Eruptions. Yellowstone Old Faithful. Ground collapse ~ Area of NYC Material ejected ~1000 km 3. Ash Fall. Giant Caldera Volcano: Yellowstone.

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Volcanic Hazards p. 138-140, web reading

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  1. Volcanic Hazardsp. 138-140, web reading • Volcano Facts • Volcano Hazards • Fall processes • Flow processes • Other types • Predicting Volcanic Eruptions

  2. Yellowstone Old Faithful Ground collapse ~ Area of NYC Material ejected ~1000 km3 Ash Fall Giant Caldera Volcano: Yellowstone

  3. Toba, IndonesiaThe Biggest Eruption? • 75,000 years ago

  4. Toba, IndonesiaThe Biggest Eruption? • Caldera diameter 100x35 km • Volume erupted 2,800 km3 • 10 cm of ash fell in India, 3000 km away • Volcanic winter for a decade • With global cooling 3-5°C • Might have affected human evolution

  5. Volcanic Eruptions over the last 10,000 years • 1300 active volcanoes • 550 eruptions (< 2000 yrs) • <10% potentially destructive volcanoes have been studied in detail ~800 million people worldwide @ risk >50% of world’s volcanoes in nations with per capita GDP <20% US

  6. Volcanic Hazards Fall Processes Flow Processes Web reading

  7. Lava Flows Basaltic lava (low viscosity) Usually slow moving (<10 mph) Rarely life threatening

  8. Nyiragongo volcano, Congo Goma, Jan. 19, 2002

  9. Nyiragongo volcano, Congo Goma, Jan. 19, 2002

  10. Pyroclastic Flows High density mixture of hot ash, rock, and hot gases Temp. >500C Velocity > 80-100 mph

  11. Pyroclastic Flows

  12. Mt Unzen, Japan • Pyroclastic flows • Eruption in June, 1991, killed 40 journalists and 3 experienced volcanologists

  13. Ash Falls (Tephra Falls) • can cover large areas for days to weeks • ash will last on the ground for months to years • making land and water unusable • provide material for future hazards (lahars) Mount Pinatubo, Philippines June 1991

  14. Ash fall in Rabaul, Papua New Guinea, 1994

  15. Volcanic Ash–Danger to Aircraft Volcanic ash can be a serious hazard to aviation even thousands of miles from an eruption. Airborne ash can diminish visibility, damage flight control systems, and cause jet engines to fail. USGS Part of a 747 engine

  16. Volcanic Smog-Vog Lake Nyos, Cameroon Poisonous Gas Emissions CO2, SO2, HCl, HF H2S

  17. Poisonous Gas EmissionsLake Nyos, Cameroon (1986) Controlled degassing, 1995 Lake Nyos “River” of CO2 50 m thick layer Bottom of lake Saturated in CO2 CO2 gas from Magma

  18. Volcanic Landslides Mt. St. Helens May 18, 1980 Debris Flow 2.3 km3 of material Largest debris landslide in recorded history

  19. The avalanche traveled approximately 15 miles downstream at a velocity exceeding 150 mph. It left behind a hummocky deposit with an average thickness of 150 feet and a maximum thickness of 600 feet.

  20. Mt. St. Helens May 18, 1980 Figure 5.10

  21. Mt. St. Helens

  22. Lahars (Mudflows) • A mixture of volcanic fragments and water • Mudflows are channeled along valleys on the flanks of volcanoes. • Mudflows have the consistency of wet concrete and move at high speeds (up to 20-60 mph). Pinatubo

  23. Nevado del RuizNov. 13, 1985 Canyon that channeled the lahar that destroyed Armero and killed 23,000 people

  24. Town of Armero The November 13, 1985 lahar from Nevado del Ruiz

  25. Volcano Monitoring and Prediction Goal: Prevent a Volcanic Crisis from turning into a Volcanic Disaster

  26. Volcanoes of the “Lower 48”

  27. Volcano Monitoring and Prediction Long-Term based on Historical Records and Geologic History Age-dating of volcanic deposits  Eruption Frequency Types and amounts of eruption products  Size of Eruption

  28. Volcano Monitoring and Prediction Short Term: systematic observations of volcano’s visible and subsurface activity Seismicity Ground tilt Gas emissions

  29. Rising Magma Ground Deformation Rising magma and increasing pressure exerted by gases often cause volcanoes to deform, or swell, before an eruption

  30. Rising Magma Moving Magma and Volcanic Fluids Trigger Earthquakes High pressure causes rocks to break, triggering earthquakes Rising magma and volcanic gases exert pressure Magma rises into reservoir beneath volcano

  31. Forecasting Volcanic Activity • Ideal Forecast includes • Location • Timing • Character of eruption and magnitude

  32. Forecasting Volcanic Activity • Ideal Forecast includes • Location • Timing • Character of eruption and magnitude • Effective Forecasting involves • Scientists • Public officials • News media • Informed Public Friday Video Path of a Killer Volcano Mt. Pinatubo eruption of 1991

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