In slab avalanche mechanics, which factor represents the resistance along slab boundaries that must be overcome by the downslope force?

• A. Friction between slab and bed surface
• B. Snow grain bonds at slab boundaries
• C. Pinning effect of anchors
• D. Air drag on loose snow

Answer: (B)

The upslope driving force must overcome the shear resistance provided by how well snow grains bond to each other along the slab’s boundaries. This intergranular bonding gives the slab its cohesion and shear strength, so the strength of those grain-to-grain bonds at the slab boundaries is what resists the downslope motion. When those bonds are strong, the slab can resist larger shear before failing; when they weaken, the slab is more prone to sliding over the weak layer beneath. Friction at the bed surface is a separate resisting factor, but the specific resistance along the slab boundaries comes from the snow grain bonds.