Geological Hazards

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Geological Hazards
2010-06-08 14:15:02
Volcanoes Tornadoes Hurricanes Landslides Earthquakes

Geologic Hazards Final
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  1. What is a major difference in movement between landslides and earthquake?
    Landslides involve gravity, while earthquakes deal with pressure between slip planes
  2. Explain the role of water in landslides
    • Water weakens earth materials in five ways:
    • 1. Weight - Driving masses of slope is increased with water
    • 2. Interplay with clay minerals - Water molecules can attach their positive sides with the negatively charged clay surfaces
    • 3. Decreasing the cohesion of rocks -Water flowing through rocks dissolves the minerals that bind the rock together
    • 4. Subsurface erosion - (Piping) causes a system of caverns which weakens the hill
    • 5. Pressure in pores of rocks and sediments -Pressure on sediments and pore water at the surface making a collapse more likely
  3. What type of bedrock is more prone to have sink holes?
    Limestone (Karst) - formed extensively in the past when the central and southeastern US were flooded by shallow warm ocean water. The removal of water during a drought or pumping of groundwater lessens the internal support.
  4. With current world population of 6.5 billion, if we were to go back 100,000 yr with a hypothetical population of 6.5million, would we have an equal density of sink holes per unit area on Earth's surface?
    No, because there would be much less groundwater pumping/removal.
  5. Can a lack of water/drought trigger landslides? If yes, where and when did it occur?
    Yes - Sacred Falls, Oahu, Hawaii
  6. Discuss the Storrega event and compare it with the 1998 PNG event.
    Considered to be known as the largest landslides in history

    Compares to the PNG event, in that both were underwater landslides which resulted in tsunamis
  7. What is a Geotherm?
    "Conditions inside the Earth" Shows the curve in which solid earth misses the curve, but not by much.
  8. What types of warning signs may precede a major volcanic eruption?
    • 1. Earthquakes
    • 2. Bulges in the ground
    • 3. Emissions of steam
  9. What were three major types of interrelated destructive processes caused by the initial eruption of Mt. St. Helens in 1980?
    • 1. Mud flows
    • 2. Ash flows
    • 3. Ash falls
  10. Explain basaltic and andesitic volcanism
    • Basaltic Volcanism (Shield Volcanoes):
    • 1. Hotter Magma
    • 2. Less Viscous
    • 3. Relatively dry magma
    • 4. Gases easily erupted
    • 5. "Peaceful Eruptions"

    • Andesitic Volcanism (Strato Volcanoes):
    • 1. Colder Magma
    • "Rhyolites"
    • 2. More Viscous
    • 3. Wetter Magma
    • 4. Gases build up before
    • 5. "Angry" explosive eruptions
  11. What type of volcanism occurs at hotspots and mid oceanic ridge?
    Oceanic volcanoes are peaceful - Volume of magma released is larger in spreading centers.
  12. What type of volcanism occurs at subduction zone?
    Cause the tall mountains seen at the edges of the continents, but the volume of magma released at subduction zones is small compared to that of spreading centers.

    Subduction zone volcanoes are explosive
  13. Explain the sizes and shapes of shield volcano and strato volcano.
    • Shield Volcano: Flows easier, 15° (Hawaii)
    • Strato Volcano: Has difficulty flowing, 45° (Andes, St. Helens, Fugi)
  14. What type of volcano was the Mauna Loa volcano?
    Basaltic "Shield" Volcano
  15. What are volcanic bombs?
    Pieces of the Earth's crust hurtled from the volcano as projectiles
  16. What are calderas, and how are they formed?
    Volcanic depressions; formed by roof collapse into partially emptied magma reservoirs
  17. What had just happened in the middle of April that disrupted air transportation across Atlantic ocean?
    Icelandic Volcanic eruption
  18. What is the source of energy that generates a hurricane?
    Hurricanes convert the heat energy of the tropical ocean into winds and waves
  19. Why do we have a "hurricane season"?
    Warm tropical waters in the Atlantic only occur during summer months.
  20. What force causes the deflection to the right (in northern hemisphere) for air traveling to the hurricane eye?
    Coriolis Effect; point of the surface facing eastwards by its rotation. Entrained more at low latitudes
  21. Why does hurricanes die off after hitting land/continent?
    Lack of warm tropical water prevents its strengthening, and also breaks up due to the landscape
  22. The number of deaths associated with the 2005 hurricane Katrina reveals what failures in hurricane mitigation by the U.S.?
    • Failures in:
    • 1. Land-use planning
    • 2. Evacuation
  23. What is a pedestral river?
    Shape of the river is important - (Two humps) result of flooding and dumping of sediment - during the spring lots of water is dumped on the city - reason it is important is because New Orleans levee was made to accommodate the flooding from the Mississippi and not a storm surge from a hurricane like Katrina.
  24. What is fire?
    Rapid combination of oxygen with carbon, hydrogen, and other elements of organic material that produces flame, heat, and light.
  25. What are three main ingredients for fi re to occur? Can we take one out and still have fire going?
    • 1. Heat
    • 2. Fuel
    • 3. Oxygen

    Absent one of there, and a fire cannot burn
  26. T/F- The great Chicago fi re killed more Americans than any other fi re that occurred in the same year?
    No - Wisconsin fire was much worse
  27. Which wind velocity is higher in the system between hurricanes or tornadoes?
    Tornadoes - up to 500 km/h winds in its weather system
  28. Is Fujita tornado scale similar to the Richter earthquake magnitude scale?
    Tornado scale probably more empirical than the Richter Scale - Have a set range of wind velocities - more empirical and less precise. Applies to the hurricane category scales as well.
  29. What does a cold front do in tornado generation?
    Makes the system unrestrainable- Forces enormous condensation, releasing massive amounts of latent heat and resulting in higher wind speeds
  30. Is it true that most tornadoes occur in the fall?
    False - Mostly occurs in the spring, but can occur anytime
  31. Is it true that tornadoes do not hit a city? Why?
    False - Tornadoes do not discriminate, but because city buildings are generally stronger, there is less perceived damage.
  32. Explain the 1983 Bora Peak, Idaho earthquake
    • Magnitude - 6.9
    • 1. Largest recorded earthquake in Idaho
    • 2. Surface faulting associated with the earthquake
    • 3. Geologic effects included rockfalls and landslides, water fountains and sand boils, changes in the flow of spring water, and water well levels
  33. Explain the 1988 Spitak, Armenia earthquake
    • Magnitude - 6.8
    • 1. 25,000 killed, 19,000 injured and 500,000 homeless
    • 2. 16.2 Billion dollars in damages
    • 3. Surface faulting of 10km occurred

    • Poor Building Codes/Lack of enforcement
    • Bad timing (children at school)
    • Power plants/hospitals destroyed
  34. Explain the 1989 Loma Prieta, CA earthquake
    • Magnitude - 6.9
    • 1. Killed 63 people
    • 2. Occurred during the world series
  35. Explian in detail the 2010 Port au Prince, Haiti earthquake. Why were there so many deaths? How did they die?
    • 200-300,000 deaths
    • Lack of fortified housing and the fact that most of the housing was built on soil containing fluids led to liquefaction, in which all of the support structure collapsed.
  36. Convection is a process of heat transfer in fluid. Why do we have a convection in the Earth's solid mantle?
    Drives plate tectonics - expels heat from the Earth
  37. Because structures fail shear motions mostly due to S-wave, explain how bracing, retro tting columns, decoupling from ground, damping processes make structures stronger.
  38. On December 26, 2004, damages at Thailand, Srilanka, India, Madives, Somalia were cause by what type of tsunami?
  39. Explain the 2004 Banda Aceh tsunami
    • Worst hit from the tsunami generated from the earthquake off the coast of Sumatra.
    • 167,000 died and many more were injured
  40. Explain the 1999 Vanuatua tsunami
    Result of education about tsunami evacuation to the public - Earthquake caused spontaneous self-evacuation. Out of the 500 residents, only 3 died
  41. Explain the 1998 Papa New Guinea tsunami
    • *Was not a very large earthquake (6.8)
    • 1. 2200 people killed
    • 2. 10 villages eradicated
    • 3. No far field tsunami

    Generated by underwater delayed landslide (slump) triggered by the earthquake
  42. Explain the 2003 Aleutian tsunami. What is a signi cant of this tsunamigenic earthquake in terms of detecting the tsunami?
    • *Tsunami wasn't picked up at the Alaska west coast DART sites, but a new station close to the epicenter recorded the tsunami. Was interpreted that there was not a large source size, which allowed them to call off the alert.
    • 1. First successful operational use of DART sensors to call off an alert
  43. Explain the 2005 Nias tsunami. Why wasn't any far- field tsunami observed?
    • 1. Generation into shallow water
    • 2. Generation where there is an island, not water
  44. Explain the 2006 Kurile Island tsunami.
    • 1. Harbor struck 8.5 hours after seismic O.T
    • 2. Damage reached 700,000
    • 3. Wave height reached 1.7m
  45. 2004 Sumatra caused a small runup (2m) compared with Srilanka. Why?
    Pillared structures
  46. Why are pillar structures more suitable for resisting tsunami damage?
    • 1. Small dimension of the structure and steep slope minimize obstruction to the tsunami
    • 2. Run up observed is very low
  47. Explain how the DART bouy is used in tsunami warning.
    Uses a pressure sensor at the bottom of the ocean to detect the overpressure caused by the passage of the tsunami. Then relays information by satellite through a bouy

    • 1. Very complex technology - expensive to build, deploy, and maintain
    • 2. Vandalism