In a slab avalanche, the mass of descending snow may reach a speed of 130 km (80 miles) per hour and is capable of destroying forests and small villages in its path. Avalanches kill about 150 people a year in North America and Europe.
What is a slab avalanche?
Slab avalanches have a distinct, broad fracture line. They can occur only when a bonded layer of snow (the slab) is lying on top of a weak layer over a sufficiently large area. Triggering requires the application of an additional load and a slope angle of at least 30°.
What are the different types of avalanches?
Avalanches are not identical, but can be assigned to several distinct categories. Slab avalanches are especially dangerous for winter sport participants. Slab avalanches have a distinct, broad fracture line. They can occur only when a bonded layer of snow (the slab) is lying on top of a weak layer over a sufficiently large area.
What is a powder avalanche?
Powder avalanches arise mostly from slab avalanches. A powder cloud forms in the presence of a large altitude difference when a sufficient quantity of snow becomes suspended in the air. Powder avalanches can reach a speed of 300 km/h and cause tremendous damage. They occur most commonly when the avalanche danger is high or very high.
