Lecture 2 - WIldfires and Plate Tectonics

Question 1

When was the Fort McMurray fire, and how long did it last?

Answer 1

May 6th, 2016, lasted 458 days (15 months)

Question 2

What are the requirements to maintain a fire?

Answer 2

Fuel, Oxygen, Heat

Question 3

What happens to a fire on a windy day?

Answer 3

It spreads faster because it’s being moved around, and as well there is more O2

Question 4

What are the phases of a wildfire?

Answer 4

• preignition phase
• combustion phase
• extinction phase

Question 5

What two steps must occur during the preignition phase?

Answer 5

• Preheating: vegetation loses water and other chemical compounds
• Pyrolysis: processes that chemically degrade the preheated fuel (gases, ash, tars, char)

Question 6

What is required in the combustion phase?

Answer 6

Ignition! - external reactions that liberate heat and light, not a single process but continuing as the fire spreads

Question 7

What are the two types of combustion?

Answer 7

• Smouldering combustion: lower temps, no need for rapid pyrolysis
• Flaming combustion: higher temp, flames, large amount of unburned material

Question 8

How does heat transfer work in a wildfire?

Answer 8

Mostly convection, as well as radiation

Question 9

Why is it neccessary that hot air rises, cools, and sinks again?

Answer 9

Brings in fresh air/oxygen to fuel the fire

Question 10

What three factors can influence the behaviour of a fire?

Answer 10

• Fuel
• Topography
• Weather (wind)

Question 11

Fuel?

Answer 11

Smaller fuels burn most readily
Density of trees plays a part: boreal forests of canada are great for fires, close enough trees to light, but not to close to block out oxygen

Question 12

Topography?

Answer 12

• Drier fuels can be found on south facing slopes or those exposed to winds
• Fire can preheat up hill from the bottom of a valley

Question 13

Weather?

Answer 13

• Fires spread more quickly under hot, dry, conditions

- Winds greatly influence the spread, intensity, and form of a wildfire

Question 14

Spot fires?

Answer 14

Little embers blown by the wind start a new fire

Question 15

What are the two types of wildfires (in terms of what they burn)?

Answer 15

• Surface fires: close to the ground, slow moving

- Crown fires: move rapidly through the crown of a forest by flaming combustion (can be intermittent or continuous)

Question 16

What happens when fires leave a near surface, water-repellent layer?

Answer 16

Increase of surface runoff/erosion, causes landslides, debris flows, etc.

Question 17

How does climate change affect wildfires?

Answer 17

Increases the intensity and frequency of fires

Question 18

What happens when there are severe insect infestations?

Answer 18

Ex. pine beetle: kill all the trees, then the dead, dry wood lights easier and burns faster

Question 19

Fire weed?

Answer 19

Uses fire to propogate

Question 20

What are some natural service functions for wildfires?

Answer 20

• increases nutrient content in the soil
• reduces competition for sunlight and rainfall among plants
• some plants (fire weed) need it to spread seeds

Question 21

What government is in charge of fire management in Canada?

Answer 21

The provinical government, unless the fire is on federal lands

Question 22

Remote sensing?

Answer 22

Satellite imagery is used to map vegetation and determine fire potential

Question 23

Fire suppression?

Answer 23

Steer the fire into an area with no fuel (fire break)

Question 24

Prescribed burns?

Answer 24

Set smaller, controlled fires in order to reduce the amount of fuel for a forest fire

Question 25

Juan de Fuca plate?

Answer 25

The plate sitting under most of north america, vancouver area

Question 26

Inner core?

Answer 26

Solid internal core of the earth, high rempt, composed of iron

Question 27

Outer core?

Answer 27

Liquid, 2000km in thickness, similar composition to the inner core

Question 28

Mantle?

Answer 28

Solid, 3000km in thickness (THICKEST LAYER), composed of iron-rich magnesium-silicate rocks

Question 29

Crust?

Answer 29

Outer rock layer of earth, (THINEST LAYER)

Question 30

Mohorovic discontinuity?

Answer 30

separates the lighter crystal rocks (crust) from the more dense mantle

Question 31

Lithosphere?

Answer 31

Cool, strong, outermost layer of the Earth (glass) | - includes the upper part of the mantle, and the crust

Question 32

Asthenosphere?

Answer 32

Hot, slowly flower layer of relatively weak rock (plasticene) - includes the inner/outer core, lower part of the mantle

Question 33

Is the oceanic crust or the continential crust thinner/less dense?

Answer 33

Oceanic is thinner but more dense, and relatively new

Question 34

How does convection work within the earth?

Answer 34

Earth's internal heat causes magma to heat up and become less dense, then it rises, cools, and becomes more dense (falls back down)

Question 35

Seismology?

Answer 35

Study of earthquakes

Question 36

Tectonics?

Answer 36

The large-scale geologic process that deforms Earth's lithosphere

Question 37

Is the lithosphere one big slab?

Answer 37

No, broken up into lithosphereic plates which move relative to eachother

Question 38

Plate boundaries?

Answer 38

Defined by areas of seismic activity

Question 39

Seafloor spreading?

Answer 39

the growing and shrinking of the seafloor

Question 40

Spreading at mid-ocean ridges?

Answer 40

New crust is added to the edges of lithosphere plates (divergent plates)

Question 41

Subduction zones?

Answer 41

Where crust is destroyed along plate edges (convergent plates)

Question 42

Divergent plate boundaries?

Answer 42

Two plates move away from one another, creating new lithosphere

Question 43

Convergent plate boundaries?

Answer 43

Two plates collide head on - result in subduction zones at oceanic-contental collisions OR - (2) continental collision boundary crumple to make mountains

Question 44

Transform plate boundaries?

Answer 44

Edges of two plates slide horizontally past one another | - ex. San Andreas Fault

Question 45

Magnetic stripe?

Answer 45

Rocks on the ocean floor are magnetically striped parallel to mid-ocean ridges, with areas of normal and reverse magnetism

Question 46

What are the two driving forces for plate tectonics?

Answer 46

- Ridge push (gravitational push away from crests of mid-ocean ridges) - Slab pull (the weight of the plate pulls a dense ocean plate into the less dense asthenosphere), this is suggested to be the more important mechanisms

Question 47

Hot spots?

Answer 47

Volcanic centers away from plate boundaries resulting from hot material deep in the mantle - ex. Hawaiian islands, Yellowstone park