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An avalanche is a massive slide of snow, ice, rock or debris down a
mountainside. Provoked by an earth tremor, extreme precipitation or
man-made disturbances (such as a loud noise or the heavy movement of
a skier or snowboarder), an avalanche can reach speeds of over 200
m/h (300 km/h). The impact of the falling material and the winds
produced by the flow can cause extensive damage to anything in its
path. According to experts, there are some 1 million avalanches
yearly.
In the case of a snow avalanche, the new snow that
accumulates on top of another heavy layer of snow can begin to slide
down the mountainside. The risk of an avalanche can be reduced by
building a snow shed — a barrier made of rocks, soil and other
materials — or by triggering a controlled avalanche at a time when
no one is on the mountain.
The worst US avalanche occurred in 1910, when a snowslide swept
two trains into a canyon in Wellington, WA, killing 96. In January
1962, an avalanche down an extinct volcano in Peru killed 3,000.
In case of an avalanche:
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Since an avalanche always flows down the middle of a trail, be
sure to walk on the side of the trail after a snowfall.
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When an avalanche stops, snow is often packed as hard as
concrete and is very hard to dig through, making chances of
recovery and survival slim. Most avalanches that trap people are
caused by people; it is prudent to choose safe paths when
traveling on snow-covered slopes, testing for snow stability,
listening for thudding noises and watching for shooting cracks in
the ice or snow.
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Be aware of escape routes, knowing which way you would jump in
case of a sudden snowslide.
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When skiing with a partner, never travel directly above your
partner, but keep your partner in range of vision.
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If you're caught in an avalanche, call out to others in your
party so they'll know where to look for you. Then, quickly close
your mouth so it doesn't fill with snow.
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Try to grab onto a tree or make a lunge for the side of the
trail.
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If you're in a car, immediately shut off the engine in order
to avoid the risk of carbon monoxide poisoning.
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If possible, shed skis, poles and heavy packs, so you're not
dragged down more.
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Work hard using a swimming or rolling motion to try to stay on
top of the snow or work your way to the side of the avalanche; try
to keep your head upslope and avoid bumping into things like trees
or rocks.
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As the slide slows, try to get a hand or foot outside the snow
so that others will be able to see you.
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Cup an arm or hand in front of your face to form an air
pocket, and try to expand your chest.
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If buried, try to relax to preserve oxygen. Yell out only if
you hear someone directly above you.
In the case of an avalanche, the best protection is prevention;
most victims of avalanches triggered the slide that they were caught
in. Even experienced skiiers, snowboarders, and mountain climbers
often underestimate the hazard the snow poses and overestimate their
ability to cope with it. Watch out for the danger signs and take all
precautions to avoid the slide!
A landslide is a type of avalanche consisting of materials
such as rock, slag or coal. Torrential rains and storms can cause a
massive flow of mud, called a mudslide. Worldwide, there are
thousands of deaths and injuries, and billions of dollars in damage
caused by landslides. These slides are most likely to happen in
places where such slides have already occurred, at the bases of
steep slopes, at the bases of drainage channels and on developed
hillsides where leach-field septic systems are used.
In case of a landslide:
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Have a family evacuation plan including phone numbers and a
safe place to which to evacuate.
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If there is time, turn off the house utilities (gas, water,
electricity) at the main switches.
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Establish escape routes from each room in the house.
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If you are caught in a landslide, try to curl up in a ball and
protect yourself from the debris as it hurtles by.
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