Deep Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 1.5–3
Weak layers are most likely to be triggered where the slab is 2-3 feet thick and on very steep slopes over 35 degrees. Signs of instability such as cracking, collapsing, or recent avalanches may not be present before triggering a dangerous avalanche. Multiple tracks on a slope do not indicate stability with this problem type. Large triggers such as a cornice fall or multiple riders on a slope increase the odds of triggering a persistent slab. Suspect terrain includes very steep, rocky, and/or wind affected slopes where thin spots exist making it possible for humans to impact buried weak layers.
Persistent slab avalanches are capable of propagating widely across or up a slope. For this reason, it is not out of the question to trigger a larger hard slab avalanche with depths over 5 feet as a result of hitting a thin, shallow portion of the slope. Heavily wind affected slopes are where these avalanches could break deeper, such as this very large persistent slab on Lava Mountain that occurred on February 10th.
The last human triggered persistent slab avalanche occurred on March 2nd in terrain similar to this.
Photo: Dakota Richardson