Depth hoar is best described as a buried weak layer formed by growth of large crystals within the snowpack near the base.

• A. Depth hoar
• B. Surface hoar
• C. Facets
• D. Graupels

Answer: (A)

Depth hoar is a buried weak layer in the snowpack formed when grains at the base grow into large, often faceted crystals under a temperature gradient. This growth creates a layer with much weaker bonds between grains and between layers above and below, so it’s easy for stress to cause a shear failure there, especially when new snow or load is added. That combination of a distinct, deep weak layer and large grains is what makes depth hoar particularly dangerous for avalanche release.

Surface hoar, by contrast, forms frost crystals on the snow surface during clear, cold nights and only later becomes a buried weak layer if the snowpack reorganizes above it. Facets refer to angular, poorly bonded grains that can develop during metamorphism and may be part of depth hoar, but the defining feature described here is the buried weak layer near the base due to large crystal growth. Graupels are ice pellets formed by riming and are not the same kind of weak layer.