Avalanches and Snow Slides

An avalanche happens when a layer of snow becomes loose and slides downhill. Thousands of avalanches occur every winter in the mountains and are usually triggered by people. Avalanches are caused by these four factors: a steep slope, a snow cover, a weak layer in the snow cover and a trigger (such as a snowboarder, skier or explosion.)

Avalanches and Snowslides - Three Main Types

Powder Avalanches - An increasing volume of powdered snow is thrown into the air, charging down the slope like a dense cloud. It can reach speeds of 250 mph (400 kph) and can flatten anything in its path.
Wet Snow Avalanches - When the temperature warms up, snow weakens and a wet snow avalanche can happen. The snow spreads as it slowly slides. Once it stops, it settles like concrete so buried victims can't move or breathe.
Slab Avalanches - These are the most common and are usually triggered by skiers. When layers of snow don't cling together, a trigger such as the weight and tracks of a skier or snowboarder, will cause the top layer to slide. There is little chance of escaping the moving slab as it breaks and carries a victim down the slope.

Avalanches and Snowslides - Outrunning a Slide

Don't bother trying to outrun an avalanche. You won't make it. Dry slab avalanches usually cruise down a slope around 60-80 mph (97-130 kph.) They can reach these speeds about five seconds after they fracture. Wet avalanches are much slower at about 20 mph (32 kph) but it's still a miracle to outrun one.

The Most Dangerous Avalanche

The most dangerous is a dry slab avalanche - it causes the most deaths. Imagine a dinner plate sliding off a table. When the plate shatters and keeps sliding, the food on the plate hardly stands a chance. The slab shatters like glass with the victim in the middle - escape is rare.

Avalanche Facts

This usually has a lot to do with luck. But avoiding potential avalanches has to do with using your brains. Here are some avalanche facts to consider:

Your chances of surviving an avalanche are around 80% if you use/carry the proper equipment (beacons, shovel, probes, etc.).

Without proper equipment your survival chances are less than three percent.

Check the conditions and the slope stability before skiing or boarding in avalanche territory.

Skiing or boarding out of bounds increases your chances of being caught in a snow slide.

If you're caught in an avalanche, swim with the avalanche to try and stay on top.

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