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Snow has a certain amount of strength, but if you apply enough stress and overload this strength, it will fail or ‘fracture’. We call the source of the stress a ‘Trigger’.
Natural triggers are ones that come from a weather influence, for example:
- Extra weight – this could be from new snowfall, wind loaded snow, or rain.
- Rapid warming caused by warm air, sun, or rain.
Human triggers are ones caused by...you guessed it, Humans. Here are some common examples:
Below is a short video of a human triggered slab avalanche. This video has sound - please excuse his 'French'Did you notice anything about the slope before the skier triggered the slab? YES - it had several tracks already on it. We will talk more about 'Common Trigger Points' in a few pages under 'Terrain'.NOTE: Nearly all the avalanches that have killed people in the backcountry were triggered by the victim, or by someone else in their group. Knowing how to recognise and avoid terrain that has avalanche potential can help keep you safe.
- Climbing/Hiking/On foot