Card Set Information
natural hazards disasters
major review topics for test IV
What does a fire need to start?
List both natural and human ignition sources.
natural: lightning, firebrands from existing fires, volcanic eruptions
human: prescribed burns out of hand, campers
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
describe heavy fuel -vs- fine fuel and different fires of each and how they spread
heavy fuel: longer to heat & ignite
flames at higher temperature
tree trunks and large branches
fine fuel: fast-drying
easy to ignite
grass, leaves and sticks less than 1/4 inch diameter
How are fires classified?
1) ground fire in ground fuel
2) surface fire in surface fuel
3) crown fire in aerial fuel
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
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
What are the stages of combustion?
glowing and smoldering
What are some factors that influence fire behavior?
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
List primary effects of wildfires
destabilization of slopes
death of plants and animals
mineral ash enriches soil
pyrocumulus clouds can form
List secondary effects of wildfires.
soil erosion and surface runoff
debris flows and landslides
propagation of some plants
How do you mitigate for wildfires both for the public and private home?
public: flexible fire management
red flag watches and warnings
homeowner: defensible space
fire-resistant exterior construction
wet down house and surrounding areas
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