Reunavyöryjä

Reunavyöryjä, also known as slab avalanches, are a type of avalanche that occurs when a large, cohesive slab of snow breaks off from the underlying snowpack and slides downhill. This slab is typically made up of a relatively uniform layer of harder, denser snow that sits on top of a weaker, less supportive layer. The fracture line, or "crown," forms at the top of the slab, and the entire mass then detaches and moves as a single unit.

The formation of reunavyöryjä is often attributed to specific weather conditions. Persistent weak layers, such as surface hoar or faceted snow, can form during periods of clear, cold weather. When a new layer of snow falls on top of this weak layer, it can create the necessary stress for a slab to form. Temperature fluctuations and wind can also play a role in compacting the new snow and contributing to slab formation.

Reunavyöryjä are considered particularly dangerous due to their size, speed, and destructive potential. Because the entire slab moves as one, they can carry large amounts of snow and debris, posing a significant threat to anything in their path, including skiers, snowboarders, and infrastructure. Identifying potential slab avalanche conditions is crucial for backcountry safety and typically involves assessing snowpack stability through various tests and understanding current weather patterns and recent snowfall.