The European avalanche warning services divide avalanches into five size categories (based on the Canadian classification). The avalanche size is defined, among other things, by the potential damage caused.
Under this definition, fatal 'skier-triggered avalanches' are often classified as 'medium' or (barely) as 'large' avalanches and reaches considerable dimensions, being typically 150 m in length and having a slab size of some 50 m by 80 m and an average slab thickness of around 50 cm. This is equivalent to a slab volume of approximately 2000 m3 or around 400 tonnes.
Size 1: Small avalanche (sluff)
Potential damage:
Unlikely to bury a person, except in unfavourable runout zones
In extreme terrain there is a danger of falling.
Runout
Stops on a steep slope
Typical dimensions
Length: < 50 m
Volume: 100 m3
Size 2: Medium avalanche
Potential damage:
Can bury, injure or kill people
Many avalanches that kill people are classified as 'medium'.
Runout
Can reach the end of the relevant slope
Typical dimensions
Length: 50 – 200 m
Volume: 1000 m3
Size 3: Large avalanche
Potential damage:
Can bury and destroy cars, damage trucks, destroy small buildings and break a few trees
Many avalanches that kill people are classified as 'large'.
Runout
Can cross flat terrain (well below 30°) over a distance of less than 50 m
Typical dimensions
Length: Several hundred metres
Volume: 10,000 m3
Size 4:Very large avalanche
Potential damage:
Can bury and destroy trucks and trains Can destroy fairly large buildings and small areas of forest. Very large avalanches can occur at danger level 3 and are typical of danger levels 4 and 5.
Runout
Traverses flat terrain (well below 30°) over a distance of more than 50 m
Can reach the valley floor
Typical dimensions
Length: > 2 km
Volume: 100,000 m3
Size 5: Extremely large avalanche
Potential damage:
Can devastate the landscape and has catastrophic destructive potential
Typical for danger level 5
Runout
Reaches the valley floor
Largest known avalanche
Typical dimensions
Length: > 2 km
Volume: > 100,000 m3