Transcript Slide

Pg. 57
The discovery of controlling fire made it an early
technology.
Examples of Fire use today
constructive -used for our benefic
destructive -causing us grief
ADD Fire triangle
Fire is oxidation in action ..... combustion is the rapid
reaction of oxygen and organic material
burning wood: produces carbon dioxide, water and heat
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STAGES OF FIRE
1. Preheating (starting the fire):
a) water removed from plant/organic material
b) temperature of material increases – pyrolysis
(chemical structure of wood breaks down yields
flammable components)
2.) Flaming combustion stand back!!!
burning=lots of energy released
3.) Glowing combustion –
no flames but those embers are hot!
FIGURE LINK
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HOW DOES FIRE SPREAD?
1) slowly along the ground
glowing combustion dominates
2) wall of fire - flaming combustion dominates
3) crown fire -fire in tree tops similar to wall of fire just
in the tree trops
ADD Ladder Fuels -stepping up from one fuel level to
the next.
ND pg. 407 Fig. 14.2
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WHAT HELPS THE SPREAD OF FIRE?
1) Wind - pushes fire, feeds with oxygen
2) Fuel: Type of vegetation burning & how much
Oils in wood (eucalyptus)
highly flammable (chaparral) vs. flame resistant
a.) Branches close to ground or not
b.) Lots of shrubby under story
Remember ladder fuels.
c.) Slash- brush piles left from clearing vegitation
3) Moisture - wet or dry and for how long
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WHAT HELPS THE SPREAD OF FIRE?
4) Topography of land - hills - fire burns faster up
slope - (convection =heat rises so preheats)topography effects vegetation types
5) Positive feedback - fire creates unstable air and
may create fire tornado-carry burning debris and
start new fires.
Heat rises, sucks in oxygen from sides=more
combustion-compare to in space to the make point
Positive Feedback is a “Vicious Cycle” but it is
“positive”?
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HOW DO HOMES CATCH ON FIRE?
1.) Physical contact -Flames travels right to home
2.) Radiant heat causes home materials to ignite.
warming your hands but be careful
*Flames do not have to touch the house.
3.) Firebrands- glowing embers blown by the wind to
new areas.
ADD pg. 58
WHAT TO DO….
1.) HOME DESIGN
A.) set back from top of slope- 100 ft minimum.
ND pg. 420 fig. 14.25
B.) building materials -flammable vs. nonflammable
C.) design- no overhanging decks/eaves
D.) wide, easily accessible driveways
E.) Roof- fire proof because of firebrands
ND pg. 419 fig. 14.23
WHY?? on all
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WHAT TO DO….
1.) LANDSCAPING
A.) keep a 30’ barrier around home
B.) Keep trees trimmed (side and over roof)
C.) use fire resistant plants -succulent ice plant
ND pg. 421 fig. 14.26
D.) Keep surrounding forest thin-ladder fuelsremove ground level that could spread to
crown
E.) keep slash -dead stuff cleared out.
Results: ND pg. 418 fig. 14.22
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WHERE DO FIRES OCCUR?
General Trend:
Regions that experience wet and dry seasons
(wet=plant growth dry=fire) Drought areas
Examples:
1.) Great Lakes 1871
clearing fields for ag. use = lots of wood debris left.
Long dry spell.
Strong winds.
Result - huge area burned farms and towns:
Peshtigo, WI wall of flames moved fast 1100+ casualties
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2.) Chicago, IL-Oct. 8, 1871
Legend: Mrs. O’Leary’s cow kicked a lantern
over = wind whipped flames - heart of the city
burned, 300 casualties.
ADD
1.) Unusually dry summer
2.) City had just finished building sidewalks out of wood
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3.) CALIFORNIA ( S.F. and S. Calif.) is a location
where fire is always a hazard certain times of year.
WHY?
a) vegetation type (chaparral - very flammable
fire species - need fire to reseed)
b) hilly - fire races uphill- CONVECTION
c) homes built close to vegetation and on steep hills
d) drought not uncommon
e) warm winds common
f) people/wacko in the woods - can start fires - arsonist
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Baja vs. Southern California
Southern California
1.) Fires in the early, cooler, wetter season are put
out quickly-allows maximal plant growth.
2.) This leaves (not intended) lots of highly flammable
chaparral to burn in the drier autumn.
3.) Fires are fought energetically and with lots of $
a.) leaves behind dense overgrowths of chaparral.
b.) as chaparral grows it becomes more flammable.
4.) Warm, dry winds occur in autumn when we
have lots of fuel
RESULTS: leaves lots of flammable fuel for the hot dry
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Baja vs. Southern California
Baja
1.) Fires are NOT fought energetically and with
little $
a.) leaves little overgrowth of chaparral.
b.) as chaparral grows it becomes more flammable.
SO…. We have less chaparral AND it is less flammable.
2.) Warm, dry winds occur in autumn BUT don’t have much
fuel to feed fires.
RESULT: less fuel during the hot dry autumn.
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Baja vs. Southern California
Total
Area *
Area
%
% Burned Number of
Fires
Burned * Burned After
Sept. 1
S.C.
2,019
166
8.2
72
203
BAJA
1,202
95
7.9
20
488
* 1000’s hectares
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Baja vs. Southern California
Distribution:
1.) S.C. a few biggies-and burns higher %
2.) Baja a bunch of little ones
ND pg. 424 fig.14.28
*BIG QUESTION: Should we continue to fight big
fires or let the early season fires go more?
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IF YOU LIVE IN A FIRE PRONE AREA
WHAT CAN YOU DO?
1.) Build for fire
NO: Wood roof, wood house, wood deck,
no. veg. near house
QUIZ
1.) Which of the following best describes the southern
California case history (compared to Baja)
a.) let little fires burn
b.) fight little fires
c.) spend little money fighting fire
d.) results in a small amount of flammable material for
the hot dry season
2.)
A)
B)
C)
D)
Why are fires a continual hazard in southern California?
older vegetation resists burning
moist conditions are common
homes on hillsides
cool moist winds are common
QUIZ
3.) Which of the following best represents the safest
course of action when designing landscaping
a.) 50’ setback from top of slope and dense underbrush
b.) fire wood stored near the house and a 30’ barrier
surrounding the house
c.) trimming overhanging trees and removing slash(debris)
d.) building on top of a hill and planning up to the house
4.) Which of the following is significant in aiding the
spread of fires:
A) types of vegetation and topography
B) size of house and building material
C) number of rivers in area and moisture
D) how many lakes there are in an area and fuel
QUIZ
5.) What best describes how convection causes burning
A) Heat rises and fire burns up hill
B) Heat rises and fire burns down hill
C) Heat sinks and fire burns up hill
D) Heat sinks and fire burns down hill
6.) What best describes how radiation causes burning?
A)The fire has to physically touch the side of the house
B) The heat of the fire has to rise uphill to the house
C) Firebrands drift onto new areas causing new small fires
D) The flames give off energy that begins to warm things
around it without touching them
QUIZ
7.) What best describes the conditions in the
Great Lakes region in 1871
A) Dry, high winds, high topography
B) Dry, low winds, high topography
C) Dry, high winds, low topography
D) Dry, low winds, low topography
8.) Which of the following best describes a fires positive
feedback behavior?
A) a fire burning down hill causing less burning
B) A fire sends out firebrands causing the fire to get
bigger and bigger
C) moist air causing less burning
D) a fire running out of fuel
QUIZ
9) What contributed to the Chicago fires of 1871?
A)
B)
C)
D)
wooden sidewalks, dry conditions, and a cow
wooden sidewalks, moist conditions, and a cow
stone sidewalks, dry conditions, and an ostrich
wooden sidewalks, dry conditions, and an ostrich