Lesson 21- What are the causes and characteristics of wildfires? Flashcards
1
Q
What is happening to the number of natural disasters over time ?
A
- Natural disasters are more frequent than 30 years ago and are costing us more
2
Q
What conditions are required for wildfires to form?
A
- The fire triangle- heat, fuel and oxygen
- 90% of all fires are started by humans
3
Q
How many wildfires are there?
A
- More than 100,000 per year
- in recent years they have burned more than 9 m illion acres of land in a single year
4
Q
Where are they located?
A
- Mainly occur in rural areas but people are inhabiting more areas like California, Australia and Southern Europe with dry vegetation and lightening strikes as they are the most sucept to them
5
Q
Natural causes of wildfires?
A
- 300 degrees flashpoint is the most common source but sometimes can be volcanoes and earthquakes
- lack of precipitation
- natural spontaneous combustion
6
Q
Human causes of wildfires?
A
- Approximatley 90% of wildfires in California are started by people
- Due to how fire suppression leads to mass fuel build up that results in very large wildfires
- cigarettes, BBQ’s, agriculture, train lines and falling power lines
7
Q
Key condition for intense wildfires-Vegetation type
A
- Thick, close together vegetation allows fires to spread quickly and easy
- Therefore, trees and bushes lead to more intense wildfires
- Vegetation with flammable oils -Eucalyptus trees
8
Q
Key condition for intense wildfires-Fuel characteristics
A
- Vegetation should be dry to allow it to catch fire
- Finer vegetation causes fires to spread quicker but lomnger thicker forms of vegetation can also cause it to spread quickly
9
Q
Key condition for wildfires to start-Climate and recent weather
A
- Must be in a climate that has enough rainfall, but considerble amounts of dry spells and droubts to dry out the fuel
- Areas with dry seasons such as California allows for these intense wildfires
10
Q
Ground fires
A
- Ground fires burn beneath the surface, slow moving, burn with little smoke for days, weeks and months
11
Q
Surface fires
A
- Surface fires burn through low-lying vegetation such as grass, bushes and small trees. They are the most common and can move quickly and burn up to 100 degrees
12
Q
Crown fires
A
- Can spread through the canopy of trees. These are very destructive as they move quickly
13
Q
Pyrophyte plant definition
A
- A plant that is specially adapted to fire
14
Q
Passive pyryphytes
A
- Resist the effects of fire, particularly when it passes over quickly and can out-compete less resistant plants which are damaged
15
Q
Active pyrophyte plants
A
- Have a similar advantage to passive pyrophytes but they also contain volatile oils which are a form of fuel for a fire which makes the fire burn more easily
