Kinds of Avalanches - Snowmobilers

Kinds of Avalanches

Avalanches come in many shapes and sizes. In general, there are two types for snowmobilers to consider:

1) Dry slab avalanches: Most fatalities occur in dry slab avalanches. These types quickly fracture over wide areas with the victim often caught in the middle. Dry slab avalanches can even be triggered from FLAT TERRAIN at near the bottom of the slope. Fractures can propagate through the snow at speeds of 50-200 mph. Victims like the skiers in the video to the right rarely have a chance to escape. When climbing snowmobilers frequently do not have the ability or momemtum to get off the moving slab. Occasionally riders can escape the slab when descending and near the bottom. See Anatomy of a Slab Avalanche* below...*
2) Wet avalanches: These types occur when warm temperatures weaken the bonds between layers in the snowpack. Wet avalanches sometimes look like concrete quickly pouring down a slope. Look for them: If temperatures have been above freezing for extended periods. When daytime temperatures rise rapidly and snowballs or pinwheels begin rolling down slopes. If you squeeze a hand full of snow and it makes your glove wet or if water literally drips out of the snow

Anatomy of a Slab Avalanche
Mouse over the terms below and get the definition for each

2) Sluffs or loose snow avalanches: Sluffs are cold snow powdery surface slides that typically are the least dangerous type of slide; however, sluffs can and often do injure snowmobile riders by pushing them over cliffs and rock bands in steep terrain.

Click on the video on the right to see some sluff avalanches in steep gnarly terrain. Sometimes you can ride next to them or through them but if they knock you over in the wrong spot they can definitely ruin your day.

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