Wildfire hazards are dangerous Flashcards
How fast can wildfires travel in forests?
6.7 mph
How fast can wildfires travel in grasslands?
14 mph
How might a wildfire spread?
Jumping or spotting - winds carry firebrands (hot wood embers) through the air
What can spotting cause?
Hot embers and firebrands to ignite fuels downwind from the fire
In Australian bushfires how far away are spot fires known to occur?
20 kilometres from the fire front
What impacts do large wildfires have on their immediate vicinities?
As air rises as its heated, powerful updrafts will draw in new, cooler air from surrounding area in thermal columns.
Differences in temp and humidity will cause pyrocumulus clouds, strong winds and fire whirls with the force of tornadoes at speeds of more than 50mph
What are pyrocumulus clouds?
Grayish or brown in colour because of the ashes and smoke of the fire
How may the thermal heat from a wildfire effect rocks and boulders?
Through weathering, the heat can rapidly expand a boulder and thermal shock can occur, may cause an object’s structure to fail
What is the ladder effect?
Describes the way a fire moves from ground to the canopy of the forest through a step-by-step process
What is the local distribution of wildfires?
The vegetated areas of Australian Western Cape of South Africa and throughout the dry forests and grasslands of North America and Europe
Where are wildfires common?
In places where climates are moist enough to allow the growth of trees and shrubs, but have extended dry, hot periods
Whats an example of a plant which enhances a fire?
Cistus monspeliensis and Australian Eucalyptus tree
How does the cistus monspeliensis enhance fires?
It has evolved to burn. The fire will mechanically rupture the seeds of Cistus, the smoke and heat will trigger germination of the next generation
How does the Australian Eucalyptus tree enhance wildfires?
It is full of VOCs (Volatile Organic Compounds) that are highly flammable and encourage the fire to develop once they are alight
What is an example of a plant which resists fires?
Pinus Pinea
How does the Pinus Pinea resist wildfires?
It is a passive pyrophyte
What is the frequency of wildfires?
The number of fires are decreasing due to the fact we are able to identify, protect, and response better than ever before
The area affected is increasing - only reasonable answer is global warming
How are wildfires caused?
90% are caused by humans - arson, campfires, cigarettes, burning debris, fireworks
Remaining 10% are started by lightening of lava
What is the El Nino phenomenon?
It dictates weather in Australia and influences the climate
What is the El Nina?
Easterly winds push warm water along the equator, over too the west
The lack of warm water along the coast of America leads to the pull up of cold water to replace the missing warm water (upwelling)
This leaves the coast of America very dry (lack of rising air), unlike Australia, where the warm water evaporates, rising into the air where it cools and condenses, forming clouds
When does the pattern of El Nina reverse?
Every 7 years
What is the El Nino?
The reversal of the El Nina
What is the El Nino phenomenon?
East trade winds weaken, therefore the warm water doesn’t fully get pushed over, subsequently rainfall falls elsewhere, and dry air circulates around where rainfall takes place, leaving the east coast of Australia in risk of drought.
How does conduction spread a fire?
Conduction is the transmission of heat through material/
Fire brands produce ferocious specs of fire embers which conduct bits of fire up to 1km away producing spot fires