Avoiding Avalanches
Avalanches are probably the most fearsome hazard in the winter backcountry because they are both lethal and hard to predict. Everyone who travels in the high country in winter should take an avalanche seminar. Local mountaineering and search-and-rescue groups often offer such seminars; check with your local outdoor shop to see who offers one in your area. What follows is merely the basics.

Avalanches are most common on slopes ranging from 30 to 45 degrees in steepness, but they can occur even on more gentle slopes when conditions are very unstable. They occur most frequently on slopes that are heavily loaded with snow by the wind. Wind-scoured, west-facing slopes are generally safer than east-facing slopes where that wind-scoured snow is subsequently deposited. Cornices – overhanging wave-like formations – frequently form at the top of dangerous, wind-loaded slopes. Avalanches can be triggered by the collapse of a cornice, by the addition of snow to a slope by wind or a snowstorm, or by the weight of a skier or snowshoer. Many avalanches run during and immediately after large storms. Gullies and broad concave bowls accumulate snow and are therefore more dangerous than ridges, where the snow pack is usually more shallow. However, travelers on ridges should take care not to walk on top of cornices, which can collapse under their weight. Not all steep slopes will avalanche if you ski them, but predicting which ones will slide and which won't is nearly impossible. A trained observer can gain some clues by digging a snow pit and examining the layers in the snow pack, but digging a pit and then deciding to ski a slope because you think it's safe is like betting your life on a fortune-teller's reading of tea leaves.

To avoid avalanches, stay off open slopes between 30 and 45 degrees. Widely scattered trees will not necessarily protect you. To be safe from avalanches, a forest must have trees that are too closely spaced to provide enjoyable skiing. Give avalanche runout zones a wide berth. Avalanches that have fallen a considerable distance build up enough momentum to travel for long distances on flat ground. Finally, listen for warning signs. An unstable snowpack, even on level ground, will frequently settle with an ominous whompf! under the weight of your skis. The sound is caused by the collapse of weak layers in the snowpack. If you hear the snowpack settle, exercise even greater caution than normal. Many people have been hit by avalanches even though they themselves were on nearly level ground. The snowpack settled beneath their skis, and the fracture propagated uphill into the avalanche starting zone. The avalanche broke loose high above them, then swept down and engulfed them. Give avalanche runout zones an even wider berth than normal when you hear the snowpack settling beneath your feet.

Everyone traveling in avalanche terrain should be equipped with an avalanche beacon, a device that transmits a signal which other avalanche beacons can hear. If one member of a party is buried by an avalanche, the other members can set their beacons to receive the buried beacon’s signal and so locate the victim. The newest models can provide the distance and direction to the buried beacon; older models simply beep ever more loudly as the rescuer comes closer to the victim. In addition to a beacon, every member of the party should carry a stout shovel. Avalanche debris sets up like concrete and time is critical. Only half of avalanche victims survive the first 30 minutes of burial. Extricating a buried victim quickly requires an aluminum-bladed shovel.

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