Loose snow avalanches account for only a small percentage of deaths and property damage. “Slab” avalanches (the most lethal) are cohesive plates of snow sliding as a unit.
Each year avalanches kill more than 150 people worldwide.
In 90 percent of avalanche accidents, the victim or someone in the victim’s party causes the snow slide.
The human body is 3x denser than avalanche debris and will sink quickly. When the slide slows, clear air space to breathe, then punch your hand skyward. Once the avalanche stops, it settles like concrete.
Unlike its portrayal in movies, noise does not trigger avalanches. Avalanches are caused by four factors: a steep slope, snow cover, a weak layer in the snow cover and a trigger.
An avalanche is often triggered when a person’s body weight provides just enough extra stress to collapse the weaker layer below.
Avalanche risk is at its greatest 24 hrs. following a snowfall of 12 inches or more.
These moving masses can reach speeds of 80 miles/hr. within about 5 seconds.
Any slope capable of producing an avalanche eventually will. Cracks and whooping sounds are good warnings of a pending avalanche.
If a victim can be rescued within 18 minutes, the survival rate is greater than 91 percent. The survival rate drops to 34 percent in burials between 19 and 35 minutes.
The primary cause of death among all people completely buried by an avalanche is asphyxiation (aka severe lack of oxygen to the body).