Avalanches Facts

Avalanches Facts
An avalanche occurs when snow rapidly flows or slides down a slope, and it is also often referred to as a snowslide or a snowslip. An avalanche can be the result of loose snow, which tends to not be as destructive or lethal, or it can be from a slab of snow that slides as a unit and engulfs and destroys almost everything in its path. Slab avalanches are the most deadly. Avalanches result when there is a steep, snow covered slope with a weak layer in the cover, and a trigger sets it off. Most avalanche accidents are the result of the victim or someone in their group causing the avalanche to start. Roughly 150 people die each year around the world from avalanche accidents.
Interesting Avalanches Facts:
Most avalanches occur on a slope that has an angle between 30 to 45 degrees as steeper slopes slough off the snow continuously, which avoids snowpack buildup.
The most risky time for an avalanche is in the 24 hours following a 12+ inch snowfall.
An avalanche can reach high speeds in a short period of time, as fast as 80km an hour in only 5 seconds.
In some areas prone to avalanches crews will trigger them under safer conditions to reduce the buildup on dangerous slopes.
The human body sinks in avalanche debris quickly. After the avalanche snow slide has begun to slow, a buried victim should clear space to breathe and punch their hand upward, before the snow slide stops as the snow becomes like concrete immediately.
The survival rate of a victim buried by an avalanche is 91% if rescued in 18 minutes or less.
When rescue occurs between 19 and 35 minutes after the avalanche, the survival rate of victims is only 34%.
The main reasons that people die in an avalanche are due to wounds, hypothermia, and suffocation. Only one in three people that are buried during an avalanche are found alive.
The worst avalanche disaster in the United States took place in 1910. A train wreck triggered the avalanche and approximately 96 people died as a result.
Avalanches can occur as a result of snow build up that was wind driven and not from direct snowfall.
A snowpack can be weakened by very cold, hot, or windy weather.
Preventative measures are often taken in areas where human life is threatened by avalanches. Repeatedly traveling on a snowpack can help to stabilize it. Explosives can be used to trigger small avalanches.
When explosives are used they can be delivered by hand, dropped by helicopter, or even shot as a projectile to its intended target area.
It is estimated that approximately 40,000 to 80,000 soldiers died during World War I as a result of avalanches at the Austrian-Italian front.
In the 1955-51 winter season, there were 265 people killed in avalanches in the Alps of Germany, Italy, Switzerland, France, and Austria. The avalanches became collectively referred to as the 'Winter of Terror'.
In 1999 in Montroc, France, an avalanche killed 12 people in their chalets after burying them in 100,000 tons of snow.


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