AVALANCHE AWARENESS

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AVALANCHE AWARENESS
for Snowmobilers
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U.S. Avalanche Fatalities by Activity1950/51 to
2000/01
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U.S. Avalanche Fatalities by Activity1993/94 to
2000/01
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TYPE OF RESCUE (US) 1950/51-1998/99
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With avalanches you have three choices

• Avoid avalanche terrain
• Learn about avalanches, minimize your risks
• Roll the dice (or pull the lever!)

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POINT RELEASE aka SLUFFS
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SLAB AVALANCHE
Starting zone
Track
Runout zone
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• Slab Avalanche
• Crown face
• Bed surface
• Flanks
• Stauchwall

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A slab is just a cohesive mass of snow
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Slab avalanches can propagate for long distances
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WET SLAB
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KEY FACTORS

• Terrain
• Weather
• Snowpack
• Human Factors

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TERRAIN

• Is the terrain capable of producing an avalanche?

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RECOGNIZING AVALANCHE TERRAIN

• Factors to consider
• Slope angle
• Slope size and consequences
• Slope shape
• Vegetation/trees
• Runout
• Aspect w/respect to wind
• Elevation

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60 deg
Slope Angles
45 deg
30 deg
15 deg
0 deg
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Slope Shape
convexity
concavity
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Size doesnt matter
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Vegetation damage is a sure-fire indicator of
avalanche terrain!
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Vegetation damage is also a helpful indicator of
runout!
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TERRAIN TRAP!!
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INDEPENDENCE SLIDE, BIG TIMBER, MTFebruary 24,
2001
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Trigger Point
Burial Point
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500 FOOT FRACTURE
TRIGGER POINT
800 FOOT RUNNING DISTANCE
BURIAL
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2 TO 3 FEET DEEP
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CROWN FACE PROFILE
DEPTH IN INCHES
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NEW SNOW
WIND SLAB
NEAR-SURFACE FACETS
CRUST
RELATIVE HARDNESS
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Burial Point
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Victim was buried 5-6 feet deep!
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WEATHER

• Is the weather affecting the snow stability?
• Snow and Rain
• Wind
• Temperature

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Wondering what the winter will be like?
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More Snow Equals More Avalanches!!
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LIONHEAD AREA, WEST YELLOWSTONE, MTApril 4, 2001
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Victims Track
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Crown is 6-8 feet deep
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PATH
75 Feet
Victim
Snowmobile
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BURIED 2 FEET DEEP
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SNOWPACK

• Could the snow slide?

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Stress vs. Strength
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Surface Hoar
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Faceted Snow
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HENDERSON MOUNTAIN, COOKE CITY, MTFebruary 4,
1992
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HUMAN FACTOR

• Are you willing to make an objective assessment
  of the avalanche danger?

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CALL YOUR LOCAL AVALANCHE CENTER
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Pay Attention To OBVIOUS Signs of Instability
These include collapsing, cracking or
whumphing of the snow, and
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Recent avalanche activity
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Snowmobiler highmarking adjacent slope
Investigating avalanche from day before
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Everyone is facing uphill, engines off, with
nowhere to run.
Yesterdays Slide Path
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Investigating crowns can give you valuable
information about the snowpack!
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Test Small Slopes
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Poorly executed highmark
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Descending a slope from the top is safer than
riding up from the bottom
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Ride the slope one at a time!!
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• 63 of snowmobile avalanche accidents occur
  while highmarking
• Bottom Line if youre going to highmark dont
  expose more than one rider at a time on the slope

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Dont ride up to help out your stuck buddy!!
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CARRY RESCUE GEAR!!
Or better yetmake sure your PARTNER has rescue
gear!
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KEY POINTS

• Ride the slope one at a time. Dont ride up to
  help dig out your stuck partner.
• Recent avalanches are an obvious sign of
  instability, so dont play on adjacent slopes
  blindly.
• Test lots of small slopes on your way in and get
  off the packed trail as much as you can. Get off
  your machine and walk around occasionally.
• Riding a slope from the top down is a safer
  option than from the bottom up, because you are
  facing a better direction if anything goes wrong.

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• If the goal is to highmark then gather as much
  information as possible on initial passes by
  riding low and fast and not getting stuck. Turn
  away from the center of the slope.
• If youre at the bottom waiting your turn and
  cant avoid sitting in a big runout zone, keep
  your machines running and pointed away from the
  slope for a fast escape.
• Carry rescue gear on you and know how to use it.

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Putting it all together
Recognize that patterns exist based on elevation,
aspect and slope angle!
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SAFE TRAVEL
Slope angle, aspect with respect to sun and wind,
consequences, slope shape, trees, runout,
elevation, patterns of avalanche activity
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Created by

• Gallatin National Forest Avalanche Center
• US Forest Service National Avalanche Center
• Photographs courtesy of
• Doug Chabot, Tom Evans, Ron Johnson, Lance
  Reik,Karl
• Birkeland, Bruce Tremper, Scott Schmidt, Ian
• McCammon, Don Bachman, Doug Fesler/Jill Fredston
• and CAIC.
• Special thanks to Doug and Jill for using their
• Terrain/Weather/Snowpack method from Snow Sense.