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:
• Climbing/Hiking/On foot
Here is an example of an intentional human triggered avalanche:
Here is an example of an accidental human triggered avalanche. Note how the consequences of this slab avalanche are very high. The slide takes the skier over cliffs and into a narrow gully.
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.