Hazards - Fires In Nature Flashcards
How does a wildfire spread?
1) Ground – fire spreads burning tree roots, peaty soil and coal underground. Slow smouldering with no flame and little smoke.
2) Surface – low-lying vegetation and leaf litter burned. Low or high intensity.
3) Crown – fire burns rapidly through tree canopy. Intense and fast-moving.
What are some human causes of wildfires?
1) Arson
2) Discarded cigarettes
3) Unextinguished
4) Glass/solar rays
5) Slash and burn farming
6) Electricity pylons
What are some natural causes of wildfires?
1) Lightning
2) Volcanic eruptions
3) Spontaneous combustion
What vegetation type is needed for the formation of wildfires?
Moist results in low-intensity fire whereas dry creates high-intensity. Thick undergrowth and densely grouped trees allow fire to spread more rapidly. Eucalyptus and pine trees contain volatile oils in leaves and bark increasing intensity of fire. Finer material catches fire more easily.
What type of climate/weather is needed fo the formation of wildfires?
Hot , low humidity climates promote fire spread. Usually occurs in areas with distinct dry season where rainfall is low for a time. Vegetation and ground is less damp so catches fire more easily. Indian Ocean Dipole is the atmospheric disturbance caused by difference in sea temperature. Results in rainfall decrease and temperature increase in Indonesia/Australia.
What type of wind is needed for the formation of wildfires?
Strong winds feed fire with oxygen, spreading burning embers influencing fire direction. Changing winds makes fire unpredictable.
What type of topography is needed for the formation of wildfires?
Fire travels faster uphill so wildfires are more intense and fast spreading in upland areas.
What are anabatic winds?
A warm wind which blows up a steep slope or mountain side, driven by heating of the slope.
What are katabatic winds?
Downslope winds that carry high-density air from higher elevations down the slope.
How is prediction used in response to wildfires?
Australian Bureau of Meteorology predicts fire spread identifying areas where evacuation was necessary. Weather forecasts can foresee periods of drought and high temperatures. Changes to wind direction can make fires spread unpredictably.
How is prevention/preparedness used in response to wildfires?
Controlled burning of vegetation. Educating public on dangers, using campfires and evacuation procedures. Fire warning systems, air patrols and lookouts.
What are some responses to wildfires?
Firefighters spray fire with water and extinguishing foam. Fire-retardant chemicals ejected from airplanes. Fire breakers - removing lines of vegetation and digging trenches. Back-burning – areas ahead of fire’s path are cleared of vegetation to remove fuel supply.
What are crown fires?
Burnt though the canopy layer which is the top layer of vegetation. They are usually the most dangerous and destructive type of wildfire because they move quickly and often produce intense heat and flames.
What is a wildfire?
Uncontrolled fires that occur in natural areas such as forests and grasslands.
What are groundfires?
Burn beneath the ground surface with tree roots and peat layers burning. They are smouldering, slow moving fires that can burn for days and weeks with no visible flames and little smoke.
What are surface fires?
Burn through low-lying vegetation such as grass bushes and small trees. They are the most common and can move quickly.
What are some natural causes of wildfires?
- Lightning strikes
- Volcanic eruptions
- Heat from the sun (UV rays)
What are some human causes of wildfires?
- Campfires and barbecues getting out of control
- Cigarettes being discarded when they are still lit
- Sparks from machinery or power lines
What must a natural fire have to occur and spread?
1) An ignition source - in the case of natural fires, lightning is by far the main cause. Climate will affect the frequency of electrical storms, especially when there is hardly any rainfall.
2) Fuel - the fuel has to be of sufficient quantity and dry enough to burn. Climate affects the frequency and duration of droughts as well as the type of vegetation.
How is fuel characteristics a condition for wildfires?
The amount of available fuels, such as trees, grass and dead plant materials affects the likelihood and severity of fires. Fine, dry material such as grasses and twigs can catch fire and burn very easily.
How is climate and recent weather a condition for wildfires?
Dry weather and droughts dry out vegetation an increase its flammability. High temperatures and heatwaves increases rates of evaporation. Strong winds can fan the flames of a fire and cause it to spread more quickly.
How is fire behaviour a condition for wildfires?
Refers to the physical characteristics of a fire such as its intensity, rate of spread and flame length.
How is vegetation type a condition for wildfires?
Denser vegetation tends to lead to more intense fires that can spread quickly and burn for longer. Some types of vegetation are more flammable than others.
What is the process of adaptation in response to wildfires?
Ember and heat resistant building materials.
What is the process of prevention in response to wildfires?
- Education
- Managing the vegetation using firebreaks, for example.
What is the process of mitigation in response to wildfires?
- Advice on how to reduce and prevent property damage.
- Fire resistant landscaping
What is the process of preparedness in response to wildfires?
- Education
- Community action
- Computer modelling
What are some primary impacts of wildfires?
- Loss of life
- Loss of property
- Release of toxic gases and particulates
- Loss of wildlife
- Damage to soil structure and nutrient content
What are some secondary impacts of wildfires?
- Evacuation
- Increased flood risk
