The Late Hour Of Avalanches

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Of the ten off-piste ski avalanches during the period studied, seven took place between 1pm and 3 pm and the three others around 11.30 am. There seem to be two affects at work, nibbling at the ski area and acclimatisation to risk. As the day goes on skiers exploit more and more of the slopes, including those they judged as too dangerous in the morning.

But why do skiers lose this perspective on danger? One hypotheses is that the pleasure of skiing in endless powder numbs the sense of danger. Skiers who start early will, given the choice, select the least dangerous slopes (we are assuming that they are equipped to make a rational choice of course). As the day goes on the areas of virgin snow are rarer and rarer and because of the selection process naturally riskier, at the same time the stability of the snow mantle has continued to evolve. However haven't they already skied many similar slopes today with no harm, as the saying goes 'a virgin slope at midday is already a future avalanche". Off-piste skiers are caught by their own game when they head for virgin powder in the afternoon, on the same slopes they identified as dangerous earlier in the day.

It appears that the cause off-piste avalanche accidents are as much if not more the result of a faulty risk analysis by the skiers themselves as caused by an degradation in the stability of the snow pack. In volume 68 of the revue, Neige et Avalanches Alain Duclos describes an accident that seems to fit this pattern: "at the time of the avalanche all the off piste visible from the lifts had been skied." The snow was cold on the surface, between -5° to -7°C which rules out a degradation in the snow mantle.

Categories: Snow Safety