Bushfires Flashcards
(38 cards)
The fire triangle has three elements
Oxygen, heat, fuel
The greater the fuel load the _____ the fire is
Hotter
What accounts for over half of bushfires?
Lightning
Do Flames at the fire front ignite anything flammable?
Yes
What is the most dangerous type of fire front?
Running crown fire
How do spot fires start?
When hot embers or debris are picked up by the wind
How far can embers fly in the wind?
Up to 30 Kms
How fast do grass fires pass?
5-10 seconds
How long do grass fires smoulder for?
Only Minutes after fire has passed
How intense are grass fires?
Low to Moderate
Do bushfires move faster than grass fires?
No
What are hotter bushfires or grassfires?
Bushfires
How do Australian eucalypts survive in times of drought?
By reducing water loss by shedding their leaves
Why do eucalypts contain aromatic oils and waxes?
To discourage insects from eating them
The low water content along with the oils characteristic of eucalypts in drought means?
They burn explosively in bushfires
When a fire passes through three crowns, they appear to explode when?
The oil rich vapour ignites in a fire ball
Bushfire conditions are dangerous when humidity is below?
25%
Fires seem to spread more quickly up?
Hillsides and slopes
Why do fires spread up Hillsides and slopes faster than flat land?
The fires preheat their fuel source with the risen hot air
Temperature rises by double every?
10 degrees of slope
Every 10 degrees of slope temperature _____?
Doubles
In what time period do eucalypt trees grow another layer of bark?
Every year
What defines a low pressure cell?
A group of isobars where the pressure decreases toward the middle
What is the type of pressure when a group of isobars where the pressure decreases toward the middle?
Low pressure system
