Card Set Information

2014-05-07 23:53:17
natural hazards disasters
major review topics for test IV
Show Answers:

  1. What does a fire need to start?
    • heat
    • fuel
    • oxygen
  2. List both natural and human ignition sources.
    • natural:  lightning, firebrands from existing fires, volcanic eruptions
    • human:  prescribed burns out of hand, campers
  3. What are the kinds of natural fuel?
    • ground:  roots, duff and peat
    • surface:  leaves, needles, twigs, logs and low brush
    • aerial:  branches, crowns, hanging moss, leaves and snags
  4. describe heavy fuel -vs- fine fuel and different fires of each and how they spread
    • heavy fuel:  longer to heat & ignite
    • burns slowly
    • flames at higher temperature
    • tree trunks and large branches

    • fine fuel:  fast-drying
    • easy to ignite
    • rapidly consumed
    • grass, leaves and sticks less than 1/4 inch diameter
  5. How are fires classified?
    • by location
    • 1)  ground fire in ground fuel
    • 2)  surface fire in surface fuel
    • 3)  crown fire in aerial fuel
  6. What are the phases of a wildfire?
    • preignition - absorbs energy
    • combustion - energy released as heat and light
    • extinction - insufficient heat and fuel to sustain combustion
  7. What is pyrolysis?
    • when volatile organic chemical compounds form fuel gas clouds
    • long-chain organic carbon molecules are broken into smaller
    • 3 products:  fuel gases, tar smoke, and char residue
  8. What are the stages of combustion?
    • ignition
    • flaming
    • glowing and smoldering
  9. What are some factors that influence fire behavior?
    • fuel
    • topography
    • weather
  10. How does weather effect wildfire conditions?
    • humidity:  ignition @ low humidity
    • fires move faster in afternoon
    • influences moisture content of fuel

    • temperature:  effects ignition point of fuel
    • peak intensity in afternoon

    • wind:  supplies oxygen, dries fuel and controls direction of burn
    • transports firebrands (embers) to ignite spot fires
  11. List primary effects of wildfires
    • destabilization of slopes
    • death of plants and animals
    • mineral ash enriches soil
    • pyrocumulus clouds can form
    • air pollution
  12. List secondary effects of wildfires.
    • soil erosion and surface runoff
    • debris flows and landslides
    • propagation of some plants
  13. How do you mitigate for wildfires both for the public and private home?
    • public:  flexible fire management
    • prescribed burns
    • fuel treatment
    • red flag watches and warnings

    • homeowner:  defensible space
    • fire-resistant exterior construction
    • disaster plan
    • emergency access
    • wet down house and surrounding areas
  14. How has Forest Service policy regarding fires changed?
    they used to put out all wildfires, but now they are picking and choosing to prevent a huge uncontrollable fire down the road