Avalanche Size
Avalanche Size : Also: Avalanche Class. In the US the five level scale is: (1) Sluff: any slide running less than 50 meter slope distance regardless of other dimensions; (2) Small: relative to the path; (3) Medium: relative to the path; (4) Large: relative to the path; (5) Major or Maximum: relative to the path. These categories are in relation to path size, so a size or class number is not so meaningful without information on, or familiarity with, the path. A reporting system used in Canada has the following size classifications: (1) Relatively Harmless, Typical Mass: Less than 10 tons, Typical Length: 10 meters, Typical Impact Pressure: 1 kPa. (2) Could bury, injure, or kill a person, Typical Mass: 100 tons, Typical Length: 10 meters, Typical Impact Pressure: 1 kPa. (3) Could bury a car, destroy a small building, or break trees, Typical Mass: 1000 tons, Typical Length: 1000 meters, Typical Impact Pressure: 100 kPa. (4) Could destroy a rail car, Typical Mass: 10,000 tons, Typical Length: 2000 meters, Typical Impact Pressure: 500 kPa. (5) Relatively Harmless, Typical Mass: 100,000 tons, Typical Length: 3000 meters, Typical Impact Pressure: 1000 kPa. Other systems have been proposed by Japanese and Swiss researchers, but have never come into use. There is an international system which is based on morphological classification. It does not have categories that could lead to a term such as 'Class 3'. (Int Comm on Snow and Ice. 1981. 'Avalanche Atlas. Illustrated International Avalanche Classification.' Paris:UNESCO 265pp.)
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