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Avalanches
Natty D Exam Notes on Avalanches
14
Bible Studies
Undergraduate 1
12/13/2011

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Term
Direct Effects of Avalanches
Definition
- impact
- burial
Term
Indirect Effects of Avalanches
Definition
- tsunami generation if the avalanche enters a lake
Term
Shear Strength
Definition
- internal resistance to movement
Term
Safety Factor of an Avalanche
Definition
Shear strength/shear stress
- if safety factor<1, the slope is unstable
Term
Shear Stress
Definition
- force causing movement parallel to slope; increases w/ slope angle
Term
Def. Loose Snow Avalanche
Definition
- surface phenomenon
- easier to get out of
Term
Def. Slab Avalanche
Definition
- more dangerous than loose slow
- slab detaches and slides down
- does not remain intact
- very hard to get out of due to huge mass and force
Term
What are the features of the head of the avalanche?
Definition
- 2X as thick as the body
- encounters friction with the atmosphere which leads to mixing of the snow
- as a result the front moves slower than the rest
- in slab avalanches it is more dangerous
Term
Describe Flow Avalanches
Definition
comes from slabs
- 5-10m in height
- collision of particles is why the avalanche flows
- interior of the flow has a high density core near the base
- particles collide resulting in heat (friction)
- when the flow stops the melted sections can freeze and set like concrete
Term
Describe Airborne powder snow avalanches
Definition
- can have a velocity of over 100 m/s
- can be over 100 m thick
- thick but dilute therefore move much quicker
- newly fallen snow becomes incorporated
Term
Describe Powder Snow Avalanche Runout Area
Definition
- flow around obstacles while flow avalanches do not
- when they hit a barrier the lower dense portion is stopped while the dilute cloud moves like a fluid over/around the obstacle
Term
Are there more or less avalanches happening in Canada? Why?
Definition
- more avalanches
- more people doing more snow related activities
- the most common triggers are human related and not natural
- dry slab most common
- leeward slopes are the most stable protected by the wind
Term
Mitigation
Definition
- avoid steep slopes and gullies
- setting off explosive charges to artificially induce avalanches and remove unstable snow can prevent avalanches
Term
Name and describe the types of engineered works that are used to mitigate avalanches.
Definition
Reforestation- stabilizes slopes and snow
Terracing- in avalanche prone zones without trees
Deflectors- to divert the flow
Arresters- slow/ stop, but be high enough or they can accelerate the intensity
Splitters- redirect around and single object
Mounds- used to slow flowing snow at the end of the runout zone
Snowsheds- allow the avalanche to pass over a structure
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