Fires In Nature Wildfires

Question 1

What is a wildfire?

Answer 1

An uncontrolled brushfire in North America.

Question 2

What are the 3 types of wildfires?

Answer 2

1. Ground
2. Surface
3. Crown

Question 3

What are ground wildfires?

Answer 3

Burn on the ground only, often below the level of leaves

Question 4

What are surface wildfires?

Answer 4

They burn on the surface of the forest with flames reaching as high as 1.3 metres.

Question 5

What are crown wildfires?

Answer 5

Burning occurs in the tree tops and spread exceptionally fast. These fires are the most destructive. A ladder effect occurs here where fires burn from the floor to the canopy.

Question 6

What is the wild urban interface?

Answer 6

Any area where humans and their development meet or intermix with wild land fuel. This is the zone of transition between unoccupied land and human development.

Question 7

What are 2 causes of wildfires? How do they spread?

Answer 7

1. An ignition source - lightning is often the main cause of wildfires and climate change increases the frequency of wildfires
2. Fuel - dry vegetation - the duration of droughts is increased by climate change

Question 8

What is the fire triangle?

Question 9

How does weather (ENSO circulation) contribute to wildfires development?

Question 10

How do winds contribute to wildfires development?

Answer 10

• Acts to drive a fire by blowing the flames into fresh fuel, providing a continuous supply of oxygen
• It causes fires to spread by causing spotting to occur (the ignition of new fires by burning embers lofted into the air by wind)

Question 11

How does topography and aspect contribute to wildfires development?

Answer 11

• Wildfires burn quicker moving up a slope, preheating unburned fuel and making them more combustible, this increases the rate of fire spread
• South and West facing slopes have drier fuels than North and East facing slopes.

Question 12

How does fuel and heat transfer process contribute to wildfire development?

Answer 12

Fuels are vegetation and structures:
- Large dense trees burn for hours (high heat)
- Dried grasses produce a flashy fire (low heat)

Question 13

How do volcanoes contribute to the development of wildfires?

Answer 13

• The red hot lava ejected can start wildfires
• Earthquakes can trigger fires through the damage of pipes

Question 14

How does lightning contribute to development of wildfires?

Answer 14

1. Hot lightning - flashes with continuing current
2. Cold lightning - flashes containing only return strokes - causes small and short duration wildfires

Question 15

What percentage of wildfires in New South Wales, Australia are caused by lightning?

Answer 15

23% of wildfires

Question 16

What are the human causes of wildfires?

Answer 16

• The act of deliberately starting fires (arson)
• Sparks from trains or machinery
• Slash and burn forest clearance

Question 17

Describe the distribution of wildfires.

Question 18

How is wildfire risk measured?

Answer 18

The McArthur FDI scale is used to represent the level of risk of a fire spreading and becoming severe once lit.

Question 19

GIve 3 primary impacts of wildfires

Question 20

Give 3 secondary impacts of wildfires.

Question 21

What is pyrophytic vegetation?

Answer 21

Plants which are adapted to tolerate fire. They may be resistant due to: thick bark, tissue with a high moisture content, underground storage structures.

Question 22

Give an example of pyrophytic vegetation.

Answer 22

The Banksia plant.

Question 23

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