Avalanche Blackwood Canyon (USA), secteur Polaris Point, Near Stanford Rocks
skiers skinned up towards Stanford Rocks. When they reached this area where
they wanted to ski, they dropped a small piece of cornice onto the slope as a
test. This cornice drop released a slab a few inches deep that propagated
widely across the slope. The first skier then started to ski the slope.
On his third turn, he triggered a slab avalanche about one foot deep that
failed within the storm snow. He grabbed onto a tree and was able to stop
himself from being taken down slope. The avalanche then stepped down another
15-20 inches to a lower persistent weak layer and pulled this skier away from
his tree and down the slope into the trees below."
"This deep slab avalanche failed within a layer of faceted snow sandwiched
between two crusts. This known persistent weak layer is located just below the
old/new snow interface. "
"The fracture was 481 feet wide (environ 146m) and ran 1235 feet (environ 376 m) through the trees downslope".
Voir les vidéos très intéressantes sur le site du Sierra Avalanche Center en cliquant sur le "lien vers une description".