Avalanche terrain: basics and limits

The most dangerous kind for winter sports is the slab avalanche. A cohesive, bonded layer of snow – the “slab” – breaks loose on a weak layer beneath it and slides off as a whole. Such weak layers can persist in the snowpack for weeks, for example when loose, angular crystals form in cold weather. A lot of seemingly firm snow can then lie on top.

Most slabs release on slopes of about 30 degrees and steeper. That is steeper than it feels, yet considerably less steep than a ski jump, and many popular winter slopes lie in exactly this range. New snow, wind that moves snow and deposits it on lee slopes, and rapid warming raise the danger. Avalanches can also run out a long way into the flatter terrain below.

Besides slabs there are loose-snow avalanches, which start at a single point and spread out in a pear shape, as well as wet-snow and gliding avalanches, which occur mainly in warm weather and rain. The European avalanche warning services describe typical “avalanche problems” in their bulletins, such as new snow, wind-drifted snow, persistent weak layers, wet snow and gliding snow, because each one has to be judged differently.

The avalanche bulletin is the most important tool anyone can use. In Europe it is based on a common five-level scale: low, moderate, considerable, high and very high. It matters not to read only the number. The bulletin also says which avalanche problems exist, at which elevations and on which slope aspects the danger is greatest and which danger signs to expect. The middle levels in particular are often underestimated.

Training is the second building block. Alpine clubs, mountain schools and comparable organisations offer avalanche courses in which you learn to assess terrain, make decisions and search and dig out people in an emergency. These courses should be refreshed regularly. This text deliberately does not explain slope and route assessment, because without training and experience it is dangerously misjudged.

Emergency equipment consists of three parts that belong together: avalanche transceiver, probe and shovel. It only helps if everyone in the group carries it and practises with it regularly. And it does not prevent avalanches. Anyone who buys equipment but does not get trained feels safer without being safer.

Without training, stay on cleared winter trails and secured pistes. Closures and warning signs exist for a reason – even if others ignore them. Tracks on a slope are no proof that it is safe; the snowpack may give way under the tenth person, not the first. Do not rest at the foot of steep slopes, because flat ground below can also be reached by avalanches.

There are alarm signs that laypeople can recognise too: fresh avalanches nearby, a dull “whumpf” sound as the snowpack settles beneath you, and cracks that shoot out across the snow. Lots of new snow, strong wind and rapid warming also belong on the list. Each of these signs is a reason to turn back and avoid steep terrain.

When someone is buried, the first minutes count. Immediately call the local emergency number (112 in the EU) and, if you are trained and have the equipment, start companion rescue at once. Do not leave to fetch help while the group can still search itself. The technique for this is learned and practised in a course, not from a text.

Getting started is easier than many people think. In winter, read your region's avalanche bulletin regularly, even on days when you are not going into the mountains. That way you learn the language of the bulletins and notice how conditions change over the season.

Then comes a basic course with an alpine club, a mountain school or a comparable organisation. After that it is best to go out with experienced, trained people or with a certified mountain guide and have the decisions explained to you. Experience grows slowly, and even experienced people stay cautious.

Even with training a residual risk remains. That is why turning back is part of the normal repertoire of every good ski tourer and winter hiker. A day on which you gave up a tour is not a lost day – the mountains will still be there next week.