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 It
was the
perfect day to hit the slopes. There was a fresh blanket of new snow,
it was not brutally cold, and the sun was shining in the bright blue
sky. It was absolutely breathtaking. The furtherest thing from your
mind was danger. You just wanted to enjoy the day. Until you heard
the rumble from further up the mountain. It became increasingly louder,
and you suddenly knew what that sound could possibly be. An avalanche.
As the wall of snow raced toward you, you took off downward, hoping
to get out of the way. Would you live or die? What could have been
done to be more aware of the situation? How do you survive an avalanche?
This page has some tips for you to help future scenarios like this.
 Avalanches
occur in mountainous areas all over the world. They occur when a slab
of snow is worked loose and slides down a mountain. Although, in many
occurances, the weight of a person on the snow can cause a slab of
snow to break away and start an avalanche, they also frequently start
without any human intervention. "Most
of the time, slab avalanches occur because the weight of new or wind
blown snow overloads the strength of the buried weak-layer. Slab avalanches
are a relatively stronger layer of snow on top of a relatively weaker
layer of snow. The weak layer fractures and the slab becomes the avalanche.
The weak layer fractures when stress equals strength. Snow can only
withstand a certain amount of stress at a certain rate. If the amount
of stress is too great or the rate is too high, then the snow fractures.
" Wind is the most common cause
of avalanches. Wind can deposit snow 10 times faster than snow falling
from storms. Wind erodes snow from the upwind side of obstacles and
deposits snow on the downwind (lee sides)." This is called "wind
loading".
 "The
added weight from snow storms also causes avalanches. If the weight
of new snow is added faster than the buried weak-layer can adjust
to its load, then it fractures and forms an avalanche. Rapid warming
or rapid melting of snow can also cause avalanches. For instance,
rain on new snow almost instantly causes avalanches. Strong sun or
warm temperatures can also cause rapid melting of the snow and creates
wet avalanches. But wind, snow or rapid warming do not always produce
avalanches. It depends on the condition of the pre-existing snow and
the conditions during the storm. With very stable snow pre-existing
snow, even heavy, new snow with wind can bond well and be perfectly
safe in the right conditions. Stability analysis is a complicated
process and it requires much study and experience to develop good
stability analysis skills."
One of the major myths about avalanches
is that they consist of a bunch or particles of loose snow. These
are called sluffs. Commonly avalanches are more like slabs of snow
that are solid and move like a sheet of snow. There are two kinds
of slabs, dry and wet. Dry slabs move very quicky, between 60 and
80 mph. Wet slabs move much slower at about 20 mph. The terms dry
and wet have to do with the texture of the snow involved in an avalanche.
Although a dry slab has the ability to be much more of a threat, both
types are to be considered very dangerous.
Do you know how to avoid avalanche conditions?
Do you know what to do should you find yourself in the middle of an
avalanche? Please read through our "Avalanche Safety Tips"
Page to learn the answers to these and other important avalanche safety
questions.
All
information obtained from www.avalanche.org
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