A deadly start to the avalanche season by Alex Deakin
Abundant snow from the Rockies to the Alps is leading to forecasts of a particularly active avalanche season this winter.
In the northwest USA, early season snow fell during October and November, providing an unstable base for the heavy December snowfall. 19 people have been killed in avalanches in the northwest over the past two weeks alone.
Ski resorts in Canada, Japan and the Alps are also feeling the effects of the early season snow. Last week, eight snowboarders lost their lives in a series of avalanches near the resort of Fernie and one man was killed in an avalanche in Austria.
Avalanches are triggered when two main factors combine; a slope (of around 35 degrees or more) and instability. Instability can be caused by snow compacting to form slippery layers, or by changes in the weather conditions, leading to thaw and refreezing episodes.
There are two main types of avalanche, loose snow and slab. Loose snow avalanches occur when powder snow cascades down slope. Slab avalanches can be much more deadly, and occur when large volumes of snow rush down mountainsides, picking up rocks and trees in their path.
For skiers and snowboarders worldwide, the first snowfalls of winter are eagerly awaited, but it is often these first snowfalls that dictate how bad the avalanches will be throughout the winter.
