 INTRODUCTION
TYPES
OF AVALANCHE
THE
MECHANISM OF AVALANCHE RELEASE
FORECASTING
SNOW AVALANCHES
AVALANCHE
CONTROL TECHNIQUES
AVALANCHE
HAZARD RATINGS
AVALANCHE
TRAINING FOR DOGS
INFO
ON THE PAGE OWNERS
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Forecasting
Snow Avalanches
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Why forecast and how do we do it?
Although
the general features of snow instability are known, many details of avalanche
formation are not clearly understood. Forecasting snow
avalanches is therefore largely an empirical art based on accumulated experience.
Known physical and mechanical principles of snow behavior
provide a qualitative understanding of avalanche origin, but quantitative
extension of these principles to specific situations is difficult,, for
nature presents too many variables to allow exact calculation
of snow stress and strength variations with time. The precise time a given
slope will avalanche cannot be predicted, but the general
degrees of instability in a given area can be estimated with reasonable
accuracy.
There
are two basic methods of anticipating avalanche hazard. One is the examination
of snow cover structure for patterns of weakness, particularly
those leading to slab avalanches. This method finds its greatest success
in forecasting climax slab avalanches caused by structural
weaknesses which may be evolved over a period of time and by a variety
of weather conditions. The second method is analysis of
meteorological factors affecting snow depositions. The latter is now successful
in forecasting direct action soft slab avalanches which run in fresh surface
snow layers where structure is poorly differentiated. In
practice the two methods overlap and both are used. Emphasis on one or
the other depends on local climate,, snow type, and avalanche
characteristics. Both apply principally to winter avalanches in dry snow;
forecasting wet spring avalanches depends on knowledge
of heat input to the snow surface as well as elements of the foregoing methods.
 Referring
to the picture on the left:
Typical
snow structure at the fracture line of a slab avalanche.Layers of new,
partly metamorphosed and old snow are separated from an icy crust by a
thin layer of very fragile depth hoar crystals. The
profile of ram resistance at right indicates low strenght in the slab layer
which slid away.
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Picture Gallery
In this section, you will
get to see pictures of avalanches happening worldwide...dated from the
1900s...
Maps of avalanche-affected
areas
Click on the globe to see
frequently hit places...
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