Which term describes a weak layer deep in the snowpack and close to the ground?

• A. Slabs on weak layers buried by one or more storms
• B. Weak layer deep in snowpack and close to ground
• C. Release of entire snow cover
• D. Top fracture surface of slab avalanche

Answer: (B)

This tests understanding of the weak layer that sits at the base of the snowpack. A weak layer near the ground is called a basal weak layer. It forms at the interface between the snow and the ground and can be made of depth hoar or other poorly bonded crystals that persist at the bottom of the pack. Because it lies deep in the snowpack, just above the ground, it can be harder to detect from the surface, yet it provides the critical plane on which a slab can fail. When a load or warming weakens or shear stress is applied, the slab above may fracture and slide on this basal layer, potentially producing a deep and powerful avalanche.

The option described matches this basal weak layer concept precisely. Other choices refer to different avalanche scenarios: storm slabs forming on buried weak layers, release of the entire snow cover (a full-depth avalanche), or the top fracture surface of a slab avalanche.