Lohkolumivyöry

Lohkolumivyöry, also known as a slab avalanche, is a type of avalanche characterized by the fracture of a cohesive slab of snow that slides down the slope as a single unit. This is distinct from loose snow avalanches, which originate from a point and spread outwards. Slab avalanches typically involve larger volumes of snow and can be significantly more destructive.

The formation of a slab avalanche requires specific conditions. A weak layer of snow must exist beneath a stronger, more cohesive layer. This weak layer can be formed by factors such as surface hoar, faceted snow crystals due to temperature gradients, or ice crusts. When the weight of the overlying slab exceeds the strength of the weak layer, a fracture occurs, initiating the avalanche. The slab then slides down the slope, often gathering momentum and volume as it moves.

Factors that contribute to the risk of slab avalanches include recent snowfall, wind loading, and temperature fluctuations. Wind can transport snow, creating thicker and heavier slabs on leeward slopes, increasing the likelihood of failure. Rapid warming can also weaken a slab or the underlying weak layer. Understanding snowpack structure and identifying the presence of weak layers is crucial for avalanche safety. Avalanche forecasting services assess these conditions and issue warnings to help people avoid dangerous areas.