Depth hoar

Depth hoar is a type of snow that is characterized by its special crystal form and is created in the wake of the so-called constructive transformation. Depth hoar is an essential and particularly insidious factor in the formation of snow boards.

Freshly fallen snow, the classic snow crystals in their hexagonal structure. Depending on various factors, inter alia, Temperature and sun exposure, these are changing rapidly by more or less in coarse-grained Altschneekristalle, which are characterized by a good bond and a corresponding strength ( this process is called degrading conversion ). Inter alia for this reason takes the avalanche danger is usually a few days after the last snowfall in most exposures significantly.

Under certain conditions, namely when the temperature gradient in the snow cover exceeds about 0.25 ° C / cm, the coarse-grained Altschneekristalle convert again and form the characteristic calyx forms of floating snow out. This process is particularly promoted by an inhomogeneous layer structure, as hard snow layers are thermally conductive, with its greater number of ice crystals, so that there is, for example, under Harsch layers at very large temperature jumps. In this area, the underlying snow depth hoar is established. Depth hoar has due to its crystal structure, only a very poor or no network. Hoar therefore trickles when it is scattered out of the hand, similar to sugar.

Depth hoar is the perfect solution as overlay for a snow board. The overlying layers then slide onto the unstable depth hoar layer. Especially with the typical combination of depth hoar under Harsch particular can transmit very large forces, the crust layer, so this combination can cause snow boards of gigantic proportions.

The particular danger of floating snow over other potential anti-friction coatings such as eingeschneitem rime is that it arises later. This may be avalanches later an already safe slope. Also, the presence of conditions under which hoar occurs much less obvious than, say, the formation of frost or snow drift. Hoar it one of the most insidious phenomena of avalanche awareness.