Snow is deposited in successive layers as the winter progresses. These layers may have dissimilar physical properties and an avalanche occurs when one layer slides on another (Surface Avalanche), or the whole snow cover slides on the ground (Full-Depth). In practice, any snow slide big enough to carry a person down, is important. Avalanche configurations are illustrated in the SAIS "Avalanche Recording Form".
Solo travellers in avalanche terrain run particularly grave hazards; skiers are in greater danger than walkers - the lateral cutting action of skis readily releases unstable snow. All off-piste skiers should use avalanche transceivers and have them SWITCHED ON before leaving base. They should carry collapsible probes and shovels. Climbers and walkers should consider the use of these items.
As of the winter of 2007, at least 702 avalanche fatalities have occurred in Canada since the earliest recorded incident in 1782. 60% occurred in British Columbia (BC), 25% in Alberta and Quebec. The reminder 10% occured in other provinces: Newfoundland and Labrador. The remainder occurred in Ontario, Nova Scotia and the Yukon, Northwest and Nunavut Territories.
