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Avalanche sizes newly named

Small becomes medium, very large becomes extreme.

by PowderGuide 12/17/2018
In order to describe avalanches - for example in avalanche bulletins, after accidents or for feedback from the terrain - standardized terms should be used for their size. From the 2018/19 season, the official EAWS terminology has been adapted to common usage in order to improve comprehensibility for winter sports enthusiasts.

This week, the Swiss Avalanche Bulletin said several times "These [avalanches] can get big". That sounds impressive - but what exactly does it mean? How big an avalanche is perceived to be is often subjective and depends on the circumstances. Nevertheless, the European avalanche warning services officially defined avalanche sizes some time ago.

Many winter sports enthusiasts are not very familiar with the terms or their definitions, partly because they often do not correspond to their own perceptions. This becomes particularly clear in the case of typical skier avalanches, which often have serious consequences for those affected, but have so far been described as "small avalanches" according to the official scale.

For avalanche sizes 1 to 5, the following terms are now used instead of the old terms

slide, small avalanche, medium avalanche, large avalanche, very large avalanche

(the rest of the classification remains unchanged):

small avalanche, medium avalanche, large avalanche, very large avalanche, extreme avalanche

Why do we need definitions?

The size designations are often used in the avalanche bulletin: In addition to the probability of triggering, the size of the expected avalanches is also important to describe the hazard situation. Only those who understand these terms correctly can interpret the avalanche bulletin correctly. Conversely, the avalanche warning service can only classify feedback correctly if it has reliable information on the size of the avalanches.

Size 1: Small avalanches (slide)

Damage potential

  • Burial is unlikely, except in unfavorable run-out areas

  • In extreme terrain, the risk of falling outweighs the risk of burial


  • Comes to a standstill in the area of the steep slope.

Typical dimensions

  • Length: < 50 m

  • Volume: 100 m³

Size 2: Medium avalanche

Damage potential

  • Can bury, injure or kill a person
    This size corresponds to the "skier avalanche".


  • Can reach the foot of the slope.

Typical size

  • Length: 50-200 m

  • Volume: 1000 m³

Size 3: Large avalanches

Damage potential

  • Can bury and destroy cars, damage heavy trucks, destroy small buildings and break individual trees.

  • If skiers are caught in avalanches of this size, the risk of death is very high.


  • Can overcome flat terrain (well below 30°) over a distance of up to 50 m.

Typical size

  • Length: several 100 m

  • Volume: 10,000 m³

Size 4: Very large avalanches

Damage potential

  • Can bury and destroy heavy trucks and trains.

  • Can destroy larger buildings and small wooded areas.

  • Very large avalanches are possible at danger level 3-Substantial, at danger level 4-Large and 5-Very Large typical.


  • Overcomes flatter terrain (well below 30°) over a distance of more than 50 m.

  • Can reach the valley floor

Typical extent

  • Length: 1-2 km

  • Volume: 100,000 m³

Size 5: Extreme avalanches

Damage potential

  • Can devastate the landscape, catastrophic destruction potential possible.

  • Typical for hazard level 5-Very large.


  • Reaches the valley floor

  • Largest known avalanche

Typical size

  • Length: > 2 km

  • Volume: > 100,000 m³

Photo gallery

This article has been automatically translated by DeepL with subsequent editing. If you notice any spelling or grammatical errors or if the translation has lost its meaning, please write an e-mail to the editors.

Show original (German)

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