
This article is part
of Willderness Way VOLUME 5, ISSUE 1. You may view
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A “flagged” tree
indicates that an Avalanche has occurred here in the
past. Notice that the uphill branches have been removed due to
past avalanche activity.

“In 1986, one of the
longest avalanche “runners” with an extremely small slope angle of 18
degrees devastated this area. “A” is where it started and “B” is
where the run out zone stopped.

Even after 13 years
the destruction of this avalanche is still evident. Notice the
pattern of the dead tree trunks.

An avalanche slid
here in the past. The bottom layers of the snow pack did not slide, while
the top layers did.


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Imagine yourself on a winter, back
country trip. It could easily be on skis, snowshoes or that brand new
snowmobile. While enjoying the scenery of the snow-covered hills and
mountains, something hits the side of your body, causing you to lose your
balance. While rolling head over heels, it becomes dark and difficult to
breath. Suddenly, all movement comes to an abrupt stop. It is dark and
cold, and you attempt to scream for help, but no one hears your pleas. As
you breathe your last breath, you wonder, “What happened?” Finally, the
breathing stops, and hypothermia begins to kill you. In this
scenario, you were caught in an avalanche. A common misconception is that,
“I would never be in an area where avalanches occur.” When watching an
avalanche released on television, they are filmed moving down high
mountain slopes. What most people do not see is that those avalanches have
been triggered by some type of explosive for film crew to cap ture. Pretty impressive, right? The majority of all avalanches
do not occur on that type of terrain. Avalanches do not occur by
accident but rather by a particular reason. As people desire to venture
further into the back country, the danger increases. We allow ourselves to
feel a false sense of security by our clothing, equipment and machines.
Mother Nature will be unforgiving for mistakes made, and believe this—she
is relentless. During my trips into the back country, I have seen on
numerous occasions snowmobiles and their tracks on snow-covered terrain
that is just waiting to slide and bury anything in its path. A video tape
can not capture the full impact of watching one occur in real
life.
In the U.S. between 1950 and 1993, 420 people are known to have
died in 310 separate snow avalanches. These are only the documented
avalanche slides. Avalanches occur almost daily during the winter season
unrecorded. So what is an avalanche? An avalanche is a large mass of
snow, ice, rock and/or debris detached from a slope and sliding or falling
suddenly downward. It can move (without including vertical drop) as little
as 100 yards or as far as a couple of thousand yards. Avalanche speeds can
range from 20 to 150 mph, depending on the moisture in the snow pack, with
snow depth ranging from 5 to 35 feet. The destruction left in its path is
unbelievable. Without getting into snow metamorphism, understand that
as snow lies on the ground, it attempts to bond with other snow crystals.
The bonding that occurs forms what is called the snow pack. Sometimes due
to various reasons, some snow crystals do not bond well with older snow,
forming a weak layer in the snow pack. As more snow falls the weight on
top of the snow pack becomes enormous. All the snow is waiting for is
something to trigger it. A trigger can be man-made or natural. The best
way to explain a trigger is to visualize an old rubber band. Snow is like
a rubber band. It likes to stretch back and forth. If the old rubber band
is pulled too fast and quickly, it will snap. As with snow, if it is not
allowed to slowly move and bend, it too will break at the weak layer. By
overloading it at the precise moment it is trying to move and bend, it
breaks. This overloading is known as the trigger. Most avalanches catching
people are triggered by people. Once the avalanche has started, it has
several parts: starting zone, track and run out zone. All of these areas
are extremely dangerous. Imagine that you trigger an avalanche in the
starting zone. The snow would immediately carry you into the track. In
this area you will find yourself being bounced off of rocks and trees,
almost like a pinball. Finally, the snow will bury you into the run out
zone. The energy and friction of moving snow will cause it to become
ice-like, so forget about being able to dig yourself out, if you are even
alive.
Understanding what an avalanche is and what it can do is the
first step. The best method of safe travel into the back country is
avalanche recognition and avoidance. Nearly all avalanche accidents can be
avoided. The signs are there if you read them. Slope angle is one of
the most important signs. Contrary to common belief, steep slopes are not
prone to avalanche conditions. This is due to the constant sloughing of
snow downslope. The majority of avalanches occur in the 30–45 degree range
which is not very steep. In fact, it is generally a great slope for
snowmobiles to conduct their “high-marking.” A clinometer on a good
compass can serve as a useful tool to measure slope angles. There are
other commercial products and math formulas that can be used to determine
slope angle. Overall, I would use extreme caution when traveling on any
slope in the 15–60 degree range. Vegetation is another sign to tell the
history of an area for such things as tracks and run out areas. Trees
missing in an open area should send up a warning sign. This means that
something has happened here in the past. Certain slops are historical
“runners.” Even though your movement may be in a tree line, continually
look at the uphill branches. Trees that are missing their uphill branches
are called flat trees. A small avalanche has occurred here in the past
which was strong enough to remove the branches, yet too weak to uproot the
trees. Small islands of trees are another sign. These islands are
usually higher than the track. Sometimes this small island may offer
protection. Look for patches of pioneer growth in a climax forest. Patches
of new trees, such as aspen growing among older trees such as pine, is
something else to pay attention to. Although these are the two signs
from nature I highlighted, there are many more. Slope orientation, slope
configuration and elevation should also be considered. Probably one of the
most important facts is information about an area from people who know the
area well. Finally, the last sign from nature is the instability and
stability of the snow pack which you are traveling on. There is no one
thing to consider, but rather several. To truly understand the snow pack,
a rutschblock should be dug to test the bonding strength of all layers. A
rutschblock is too detailed for this article but is something all back
country travelers should know how to make.
When traveling in avalanche prone areas, every one should carry
snow shovels, probe poles and transceivers. Should someone be caught in an
avalanche, time is essential. These pieces of equipment could mean the
difference between life and death for the one buried. Should you have
to travel across an avalanche-prone slope, take the following precautions;
button up your jacket and place the hood over your mouth. This prevents
snow from being inhaled and delays hypothermia. Cross one at a time while
someone is always watching. The spotter may have noticed them somewhere in
the path. Consider using the same track to minimize disturbance to the
snow and exposure time to the hazard. Finally, trail an avalanche cord of
approximately 100 feet. This can be parachute cord with brightly colored
tape attached at various points for easier identification. If caught in
an avalanche, attempt a backstroke swimming motion to stay on top of the
slide, and hopefully reducing the burial depth at the end of the ride.
Attempt to remain upright with your head uphill. If those methods are not
working, cover your face with your hands to create an air pocket before
the slide solidifies. Remain calm and quiet to conserve energy. Only call
out if you hear a rescue party, or you will use up valuable
oxygen. Statistically, after 30 minutes of burial the chance of living
is 50% and 20% after one hour. Speed is essential for recovering a live
victim. Hypothermia and suffocation are the main causes of death. A search
should not be called off for at least 24 hours. Initially, search the last
known spot and down the slope while looking for clues such as clothing and
equipment. Look on the outside of bends or the uphill side of trees and
boulders. If you have no luck during a hasty search, spare what you can
in manpower to send for help. An organized search has to be conducted
which will include probe lines, and hopefully with the use of search dogs.
Generally, by the time they arrive it is usually a body recovery
operation. Winter back country travel is a wonderful experience, but
one with many dangers. Avalanche study is a science—a science with little
understanding for the “tender-foot.” Although this article only touched
the basics on many facets of avalanches, it cannot replace the amount of
study, knowledge and experience to travel safely into a place of solace.


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