Which term is a buried weak layer within the snowpack?

• A. Facet
• B. Surface hoar
• C. Depth hoar
• D. Low density/poorly bonded layers within snowpack (graupels)

Answer: (C)

A buried weak layer is a layer within the snowpack whose strength is much lower than the layers above and below, making it prone to failure under load. Depth hoar is the classic example: it forms at the base of the snowpack when there is a strong temperature gradient over time. Water vapor moves through the snow and crystals grow into large, highly faceted grains with weak bonds between them. This results in a layer of large, poorly bonded crystals that sits within the snowpack and can trap energy until a load or rapid loading causes it to fail, often triggering an avalanche.

Surface hoar forms on the surface as frost crystals and can become a buried weak layer if new snow covers it, but depth hoar specifically refers to the buried layer at the base with large grains and poor bonding. Graupel or low-density layers describe other snow characteristics and are not the standard buried weak-layer type in this context.