A new analysis shows that there remains an unknown element of risk, which these tests cannot determine. Cross-country skiing is an exhilarating and popular sport. However, away from the prepared pistes of the alpine resorts, there is a risk of the skier triggering an avalanche and being seriously injured or killed. As the popularity of off-piste skiing increases, so does the number of casualties from avalanches.
Avalanches present huge objective danger to skiers and mountaineers.
Skiers use tests such as the 'Rutschblock' test or the 'shovel shear' test to gauge the stability of slopes. Both tests involve digging a hole in the snow and, crudely, jumping up and down, or pushing the snow sideways with a shovel to judge its strength. These tests allow the skier to identify weak layers in the snow-pack, estimate their strength and so assess the risk of an avalanche. Although the presence of a weak layer is a pre-requisite for an avalanche, the trigger for an avalanche depends on the strength of the overlying layers of snow and on the growth of cracks in the snow. In many cases, these influences increase the probability of an avalanche, so that an area may not be safe even if the standard tests indicate that it is.