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Lecture

Chapter 9 Avalanches.docx


Department
Geophysics
Course Code
GOPH 375
Professor
All

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Chapter 9: Avalanches
Presentation
Two types
o Point release usually small
o Slab avalanche big, huge chunk comes down
BC Prince Rupert slide
T_ creek 1989; 1 person killed, town was pre-warned
Avalanche consultant tell towns of potential hazards
St John’s Signal Hill national park – 1959 5 people killed, rock fall
Jan 1st 9 fatalities, 25 injured
Road avalanches;
No avalanches in Canada since 1986? But we do have many road closures
1976 last road avalanche in Canada
Kicking Horse pass - Golden BC, avalanche shut down trans Canada for 2 weeks
1979 storm across BC, Grandview chairlift
Alpine meadows 1984
Davos, Switzerland
Mitigation nets to stop avalanches
o Gazex exploders that release propane and oxygen to get a large explosion out and
release the snow. Expensive
We lose an average of one person per year from avalanches
Vast majority of fatalities are recreational voluntary risk
Skiing is in avalanche terrain
15 fatalities per year
Forecasting: stabilize slopes by using explosives. Forecasting is very experienced based
o Snow packed test determining how hard the snow is strength (how much it’s
packed)
o Ritch block test numbers 1-5 scale
o Each square is one day on 6.2 graph
Evaluator: pocket card, measures risk 8.6
Rescue gear: ballon packs inflates so that you rise higher than the flow
o Avalon put it in your mouth and it separates where you inhale/exhale from to avoid
the ice masks that forms when your exhale breath freezes snow around you
Human factors youth, snowmobilers
Transceivers: underclothing can pick up a reading from 60-70m a part. Useful for 2
snowboarders, if ones caught the other can receive a signal that tells them where they are
Purposely start small avalanches before layers build up enough to be dangerous
Avalanches are Canada’s most destructive geological forces
Gravity is the main power behind avalanches. All slopes will eventually fall; over time (creep) or
suddenly.
o Gravity pulls rocks to earth’s center with force = rocks mass X gravitational acceleration
(9.8 m/s2)
o Gravity pulls rock straight down, another force pulls it perpendicular to the slope,
causing it to roll parallel to the slope down the hill
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