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The following text has been excerpted from the book Snow Sense by Jill Fredston and Doug Fesler.
The book is distributed by the Alaska Mountain Safety Center, 9140 Brewsters Drive, Anchorage,
Alaska, 99156, (907) 345-3566.
The excerpts below are only a sampling of information essential for safe travel into the
backcountry. Before heading to the backcountry, one should plan on reading the complete
text of Snow Sense and other avalanche books, as well as attending an avalanche safety class.
In the United States between 1950-51 and 1992-93, 420 people are known to have
died in 310 separate snow avalanche incidents. Four out of five, or 80% were
recreationists and of these, roughly 75% were travelling in the backcountry. A
majority of the victims triggered the avalanches that killed them. In Canada
between 1979-80 and 1993-94, 97 avalanche fatalities occurred. All but two of
these people died pursuing recreational activities. A greater number of
fatalities occurred in Europe, with 728 deaths in 12 countries between 1985-86
and 1990-91, but the types and causes of accidents were often very similar.
These numbers represent just the fatalities in selected countries.
Hundreds more incidents occur worldwide each year in which people trigger, are
caught, partly buried, buried, and/or injured in avalanches.
The number of avalanche accidents continues to climb as winter backcountry use
and skill levels increase, available equipment improves, and "limits" get
pushed. Backcountry skiers and mountaineers lead the list of those getting
caught although during the 1993- 1994 season, most of the fatalities in North
America were snowmachiners. A rise in incidents involving snowboarders is
expected as the sport continues to gain in popularity.
These statistics are not meant to intimidate, but to educate. Most of the
avalanches catching people are triggered by people, and the same mistakes are
being made repeatedly. While some accidents are a result of not recognizing
potential hazard, most accidents occur because the victims either underestimate
the hazard or overestimate their ability to deal with it, often exercising poor
route selection or choice of timing. Many of the accidents involve
"experienced" skiers or mountain travelers. There is a tendency to assume that
these people are also experts at evaluating avalanche hazard but this is often
not the case.
Nearly all avalanche accidents can be avoided. The clues are there. The key is
to learn to read "nature's billboards." Usually when avalanche accidents are
investigated, it is found that not just one or two clues were overlooked or
ignored but three, or four, or five clues by the time the group got into
trouble. Few people would choose to cross a busy four-lane highway without
listening for the traffic or looking both ways. Similarly, travelling on or
near steep, snow-covered slopes without gathering and integrating information
about the current stability of the snow is like wearing earplugs and blinders.
Steep slopes can be negotiated safely but it is a matter of timing. When the
fish are running, some people go fishing. When the avalanches are running, it
is more important than ever to carefully evaluate snow stability and choose
good routes every step of the way. There will be some days when only lower
angle slopes can be traveled safely and slopes with angles steeper than roughly
35deg. need to be avoided. There will be other days when you can safely travel
on everything in sight, no matter what the angle.
The snowpack is stable most of the time and because of this, it is common to
travel to a particular spot in avalanche terrain many times without seeing any
avalanches. As a result, we get "positive reinforcement," that is, we begin to
think of an area as safe. But if we travel to that spot often enough, sooner or
later we will be there when the snow is unstable and it may catch us offguard.
To travel safely in dragon country, you need to think like a dragon. Learn
where they live and feed, when they sleep, and what fires them to life.
Timing is everything. You can only travel safely on red terrain when the
snowpack is a green. When instability exists, you need to notch back your slope
angles.
Measure your slope angles. This not only lets you know the capability of the
terrain to produce avalanches, but also helps you categorize the type of
instability you may be dealing with. For any given avalanche cycle or
instability, failure will occur only on a certain range of slope angles. Keep
in mind that shear failure propagation is common when a sensitive weak layer
like surface hoar or young faceted snow is subjected to a new load.
Always look for tender spots or areas of stress concentration. Likely problem
areas are rollovers, places where the slope angle suddenly increases,
wind-loaded areas, shaded aspects, thin spots, a short distance below cliff
bands or near rocks and brush where weak layers are likely to be more well
developed.
Study fracture lines. Note which slopes have slid, what the bed surface slope
angles were, where the fractures broke, what they ran on, and how deep they
were. You can learn a lot from this, including developing x-ray avalanche
eyeballs for detecting tender spots and stress concentration areas. Also
measure the runout or alpha angle, that is, the angle between the furthest
extent of the avalanche and the fracture line. This angle is an indication of
the runout distance or efficiency of a given avalanche. The lower the angle,
the more efficient and longer-running the slide. If you have a path you like to
travel in regularly, take a photograph of it and make an enlargement. Overlay
the print with a plastic mylar. Draw any avalanche activity you observe during
the season on this mylar and make a note as to contributory terrain, snowpack,
and weather factors.
Integrate clues. Continually seek bull's-eye data. Once you have an opinion
about snow stability, keep seeking additional information to confirm or refute
that opinion and to further reduce your level of uncertainty. Don't be
"suckered" in by the absence of obvious clues like recent avalanche activity,
whumphing noises, or shooting cracks. Your biggest clue may just be recent
weather events.
Hammer on the snowpack. The snow stability evaluation process does not end
until the snow melts. Do not get complacent. You can travel all day and find
your problem spot within five minutes of the end of the day. Be very careful
about climbing one aspect and travelling down another. Jump on little slopes.
Cut cornices with ropes. Do belayed jump or pit tests. If you are an expert
skier and are dealing with a surface instability, ski test small slopes when
you have a good traverse line between safe spots and a reliable partner. If it
does avalanche, take a few minutes to examine why. Keep in mind that just
because a slope doesn't go, doesn't mean that it is stable.
Analyze your assumptions / beware of the human factor. Remember that the
avalanche dragons do not care if you are tired, hungry, grumpy, or late for
work. Is your attitude interfering with your objectivity? When evaluating
avalanche hazard, you need to think like an avalanche. Do not be reassured just
because there are tracks on a slope.
Choose your travel lines carefully. For your first run, choose a slightly less
steep angle or a line off to the edge of the slope rather than center-punching
the path. Always think escape routes. Which way are you going to jump if the
slope cuts loose?
Think consequences. What's going to happen to you if you get caught or buried?
Do better alternatives exist? Is it worth it?
Be conservative. When in doubt, notch back your slope angles. If you have a
"travel to die" attitude, you probably will.
Use safe travel procedures. Travel on or near steep slopes one at a time. Be
anti-social. Never stop in the middle or at the bottom of an avalanche
slope—always stop off to the side or well out away from the runout zone. Never
travel above your partner. Keep each other in sight. Choose your partners
carefully. If skiing, use releasable bindings and do not wear safety straps on
your skis or poles.
Be prepared for the worst. Have a rescue plan and carry avalanche rescue
equipment (shovel, beacon and probe per person). Understand that your beacon is
not a safety talisman. A functioning beacon just ensures that the beacon will
be recovered and does not guarantee that you will survive the avalanche.
If you are caught in an avalanche, call out so other members of your party
know to watch you as you are carried down the slope, and then keep your mouth
closed to prevent ingestion of snow. You may have a split second to grab a
tree, dig into the bed surface, or lunge, ski or "goose" your machine off to
the side. If so, do it! (Note: If you are inside a vehicle when caught,
immediately shut off the engine to avoid the danger of carbon monoxide
poisoning.) If possible, discard cumbersome gear such as skis, ski poles, and pack (if it
is heavy) although this is much easier said than done. This gear tends to drag
you underneath the surface of the moving debris. You might, however want to
keep a light pack with you as it may help protect your back and the gear in it
will probably be useful in an emergency situation. Use a swimming and rolling motion to try to stay on the surface of the snow
and/or work your way to the side of the avalanche. FIGHT with all your effort!
You will likely be out of control but try to keep your head upslope and your
feet downslope and maneuver around fixed objects like trees and rocks. The main
message is that now is the time to struggle to stay on the surface and to avoid
hitting objects which can inflict mechanical injuries. As you feel the snow slow down, thrust your hand or any part of your body
above the snow surface so it can be seen by others. You probably will be so
disoriented that you won't know where the snow surface is so just guess and
lunge. Before the snow comes to rest, cup your arm or hand in front of your face to
clear an air space. If possible, try to expand your chest during this time. A
number of buried snowmachiners have credited their survival to the air space
provided by their helmets. If buried, stop fighting and relax to preserve oxygen. Remember, you are not
supposed to panic! Occasionally, buried victims have been found by yelling for
help but usually the hearing of the rescuers is impaired by static such as the
wind, rustling clothes, the sound of footsteps, etc. Victims can often hear
more clearly because of the absence of this static under the snow. It is
probably best to save your breath and yell only if you hear someone directly
overhead.
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