Y13 MB - Wildfires

Question 1

What is a wildfire?

Answer 1

An uncontrolled rural fire

Question 2

What are wildfires known as in Australia and North America?

Answer 2

Bushfires

Question 3

What are the three main types of wildfire?

Answer 3

Ground fire
Surface fire
Crown fire

Question 4

What is a ground fire?

Answer 4

A slow smouldering fire that burns organic matter in the soil (such as peat)
They spread slowly and at fairly low temperatures for long periods of time
There may be no flame

Question 5

What is a surface fire?

Answer 5

The burning of leaf litter and low lying vegetation
The most common type of fire
Can be low or high intensity
Cool quickly and are relatively easy to control

Question 6

What is a crown fire?

Answer 6

Fire that moves rapidly through the canopy (top layer of vegetation)
Hottest type of fire
Very difficult to contain

Question 7

What is the hottest kind of fire?

Answer 7

Crown fire

Question 8

What is the most common kind of wildfire?

Answer 8

Surface fire

Question 9

What is the process by which fire may spread from the ground to the tree canopy?

Answer 9

The ‘ladder effect’

Question 10

What is the ‘ladder effect’

Answer 10

Where fire spreads from the ground to the tree canopy by igniting low branches and shrubs

Question 11

What is needed for a wildfire to occur?

Answer 11

Ready supply of fuel (dry vegetation)
Ignition source (natural or human)
Favourable climatic or weather conditions

Question 12

Where is the only continent a wildfire can’t take place?

Answer 12

Antarctica

Question 13

Describe what conditions cause wildfires to travel faster

Answer 13

Wildfires travel faster uphill than downhill
The steeper the slope the faster they travel

Question 14

Give an example of a low heat output and high heat output area for wildfires

Answer 14

Grassland - low heat output
Forested area - high heat output

Question 15

What is the impact of eucalyptus and pine trees on wildfires?

Answer 15

They contain lots of oil so burn easily

Question 16

What are firebrands and in what conditions do they occur?

Answer 16

Firebrands are when eucalyptus trees shed long strings of bark which then encourage the rate of the wildfire spreading

Question 17

What conditions are optimum for the spread of a wildfire?

Answer 17

Rainfall sufficient for the growth of vegetation (fuel source)
Distinct dry season (when vegetation dries up it becomes more flammable)
Strong winds (provide oxygen and help the fire spread)
Cyclical climatic events such as El Niño

Question 18

What is the El Niño cyclical climatic event?

Answer 18

Westerly trade winds weaken so less warm water is transferred to the west which reduces the pressure difference between the east and the west
The temperature of the eastern Pacific Ocean rises causing warmer temperatures in South America
There is therefore more precipitation in South America so drier conditions in Southeast Asia and eastern Australia increasing the risk of wildfires there

Question 19

What are the natural ignition sources of wildfires?

Answer 19

Lightning
Volcanic eruptions
Burning fragments (firebrands) being blown ahead of flames and igniting new areas of forests - spot fires
Heat transfer processes heat vegetation further ahead of the flames causing the fire to spread more quickly

Question 20

How are spot fires caused?

Answer 20

Firebrands being blown forwards and igniting new areas of forest ahead of the wildfire front
Firebrands rolling down steep slopes and creating spot fires there

Question 21

Why are wildfires so good at climbing uphill?

Answer 21

Heat transfer processes (e.g conduction and convection) heat vegetation ahead of the flames causing fires to spread more rapidly
Hot air rises so heat is transferred vertically

Question 22

What are the human ignition sources of wildfires?

Answer 22

Discarded cigarettes
Poorly controlled campfires
Arson

Question 23

What are the areas called where woodland particularly close to urban areas is vulnerable to wildfires caused by humans?

Answer 23

Wildland-urban interfaces

Question 24

How may wildfires have positive impacts?

Answer 24

They remove dead or dying material from the forest floor as well as harmful insects and diseased plants —> encourages new plant growth
Some species of plant cannot reproduce without fire e.g the Douglas fir need fire to aid seed germination

Question 25

Give some mitigation strategies for wildfires

Answer 25

Satellites with infrared sensors to detect thermal variation
Back burning where controlled fires are lit to burn the fuel (vegetation) ahead of a wildfire

Question 26

What are firebreaks and is this an example of mitigation, adaptation, prevention or preparedness?

Answer 26

Where areas of vegetation are burned in forested areas to halt fires from spreading
Adaptation strategy

Question 27

What percentage of wildfires are due to humans?

Answer 27

85%