Bushfires

Everything you need to know about Australia's flame-filled phenomenon.

Geographical Processes Responsible for Bushfires

Go to —->
Areas Most Seriously Affected by Bushfires
The Impacts of Bushfires
The Response of Society to Bushfires

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How are bushfires caused?

There are two ways that a bushfire can be caused. These are by natural means, such as a lightning strike or due to human influence, such as arson.

Natural Means

The main way a bushfire will start due to completely natural causes, is by lightning strike. 

Did you know that a minimum of 100 lighting flashes strike our planet every second? When calculated, this totals to over 8.6 million strikes each day. Each stroke of lightning can carry one hundred million volts of electricity and can reach a temperature of over thirty thousand degrees Celsius. When this heat energy hits dry vegetation such as leaves, trees, bushes or shrubs, a bushfire can ignite.  

 Lightning is also the highest single cause of a bushfire, with 26% of fires starting this way. 

Human Means

The majority of bushfires are caused by humans, whether accidental or deliberate. 

Examples of accidental bushfires include those initiated by unattended or improperly extinguished campfires, agricultural burns that have not been monitored carefully enough, sparks or heat from machinery or equipment, car exhaust and discarded cigarettes.

Unfortunately, some bushfires are deliberately lit by arsonists and can destroy thousands of acres of land. Arson is the second most common cause of initial combustion, with 25% of fires being lit this way. 

What happens once the fire has been lit?

After the initial ignition, many factors influence the course of a bushfire. Once it has begun, a bushfire can be dealt with and extinguished quickly or it can rage out of control, and the environment has a big impact on which one of these outcomes is the one which occurs. 

These factors include

  • Lack of rainfall. A dry environment allows for dry vegetation, leaves and twigs to become fuels for bushfires. 
  • Wind. The wind provides oxygen, which a fire needs to stay strong and continue burning onwards. The stronger the wind is, then the stronger the flame becomes. As well as this, wind can carry embers into the air which are then deposited ahead of the blaze causing spotting (small fires and burnt-out areas).
  • Humidity. Humidity of less than 20% causes the fuels to dry out and consequently they become flammable.
  • Temperature. Hot air can lower the amount of moisture in vegetation, making them more efficient fuels. 

As well as these factors, the terrain on which the fire is raging can alter its speed. For example, it is known that fires have a tendency to spread quicker up the side of slopes. 

Related Links

http://clearlyexplained.com/nature/earth/disasters/bushfires.html#how

http://www.skwirk.com/p-c_s-57_u-479_t-1306_c-5027/bushfires-and-bushfires-in-australia/qld/bushfires-and-bushfires-in-australia/disasters/natural-hazards

http://www.dpi.vic.gov.au/dse/nrenfoe.nsf/LinkView/>

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Go to —->
Areas Most Seriously Affected by Bushfires
The Impacts of Bushfires
The Response of Society to Bushfires