Mécanisme de déclenchement des plaques
What we can see, playing “stability games”
L'after-eight du 22 janvier 2021 sur le déclenchement des avalanches :
Pour les plus pressés :La présentation d'Alain et François sur le déclenchement des avalanches
Les 4 étapes du déclenchement
Vidéos
Buried weak layer
Basic identification by probing with your ski pole, confirmed (or not) by the compression test.
Crack initiation
Compression test (having isolated a column of the snow pack the shovel blade is placed over the column and tapped with the hand).
Weak layer collapse
Weak layer behavior before and after the compression test.
Crack propagation
Crack initiation using a snow saw to cut the weak layer located below a long isolated slab block, then...
The breaking-off of the slab and its transportation
The « slab » must break off before it slides sliding, if the block has not been pre-cut.
« Bridging index »
Multiply the total thickness (cm) of snow layers above the weak layer by their average hardness (1 to 5). If you get less than the critical (empirical) threshold of 130, you may initiate a crack.