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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:

Size	Description	Typical Mass	Typical Length	Typical Impact Pressure
1	Relatively Harmless	Less than 10 tons	10 meters	1 kPa
2	Could bury, injure, or kill a person	100 tons	100 meters	10 kPa
3	Could bury a car, destroy a small building, or break trees	1000 tons	1000 meters	100 kPa
4	Could destroy a rail car	10,000 tons	2000 meters	500 kPa
5	Largest known	100,000 tons	3000 meters	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.)

This glossary is a work in progress and is made possible by AlpenPro.

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