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Earthsci 2GG3 > Lecture 2 - WIldfires and Plate Tectonics > Flashcards

Lecture 2 - WIldfires and Plate Tectonics Flashcards

1
Q

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

A

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

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2
Q

What are the requirements to maintain a fire?

A

Fuel, Oxygen, Heat

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3
Q

What happens to a fire on a windy day?

A

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

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4
Q

What are the phases of a wildfire?

A
  • preignition phase
  • combustion phase
  • extinction phase
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5
Q

What two steps must occur during the preignition phase?

A
  • Preheating: vegetation loses water and other chemical compounds
  • Pyrolysis: processes that chemically degrade the preheated fuel (gases, ash, tars, char)
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6
Q

What is required in the combustion phase?

A

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

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7
Q

What are the two types of combustion?

A
  • Smouldering combustion: lower temps, no need for rapid pyrolysis
  • Flaming combustion: higher temp, flames, large amount of unburned material
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8
Q

How does heat transfer work in a wildfire?

A

Mostly convection, as well as radiation

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9
Q

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

A

Brings in fresh air/oxygen to fuel the fire

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10
Q

What three factors can influence the behaviour of a fire?

A
  • Fuel
  • Topography
  • Weather (wind)
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11
Q

Fuel?

A

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

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12
Q

Topography?

A
  • 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
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13
Q

Weather?

A
  • Fires spread more quickly under hot, dry, conditions

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

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14
Q

Spot fires?

A

Little embers blown by the wind start a new fire

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15
Q

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

A
  • 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)

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16
Q

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

A

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

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17
Q

How does climate change affect wildfires?

A

Increases the intensity and frequency of fires

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18
Q

What happens when there are severe insect infestations?

A

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

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19
Q

Fire weed?

A

Uses fire to propogate

20
Q

What are some natural service functions for wildfires?

A
  • increases nutrient content in the soil
  • reduces competition for sunlight and rainfall among plants
  • some plants (fire weed) need it to spread seeds
21
Q

What government is in charge of fire management in Canada?

A

The provinical government, unless the fire is on federal lands

22
Q

Remote sensing?

A

Satellite imagery is used to map vegetation and determine fire potential

23
Q

Fire suppression?

A

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

24
Q

Prescribed burns?

A

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

25
Q

Juan de Fuca plate?

A

The plate sitting under most of north america, vancouver area

26
Q

Inner core?

A

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

27
Q

Outer core?

A

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

28
Q

Mantle?

A

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

29
Q

Crust?

A

Outer rock layer of earth, (THINEST LAYER)

30
Q

Mohorovic discontinuity?

A

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

31
Q

Lithosphere?

A

Cool, strong, outermost layer of the Earth (glass)

- includes the upper part of the mantle, and the crust

32
Q

Asthenosphere?

A

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

33
Q

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

A

Oceanic is thinner but more dense, and relatively new

34
Q

How does convection work within the earth?

A

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

35
Q

Seismology?

A

Study of earthquakes

36
Q

Tectonics?

A

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

37
Q

Is the lithosphere one big slab?

A

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

38
Q

Plate boundaries?

A

Defined by areas of seismic activity

39
Q

Seafloor spreading?

A

the growing and shrinking of the seafloor

40
Q

Spreading at mid-ocean ridges?

A

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

41
Q

Subduction zones?

A

Where crust is destroyed along plate edges (convergent plates)

42
Q

Divergent plate boundaries?

A

Two plates move away from one another, creating new lithosphere

43
Q

Convergent plate boundaries?

A

Two plates collide head on

  • result in subduction zones at oceanic-contental collisions OR
  • (2) continental collision boundary crumple to make mountains
44
Q

Transform plate boundaries?

A

Edges of two plates slide horizontally past one another

- ex. San Andreas Fault

45
Q

Magnetic stripe?

A

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

46
Q

What are the two driving forces for plate tectonics?

A
  • 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
47
Q

Hot spots?

A

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

Earthsci 2GG3 (12 decks)

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