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Avoiding Avalanches: 10 Terrain Features to Watch for


 Avoiding Avalanches: 10 Terrain Features to Watch for
 

by Editor

February 19, 2003

When traveling on snow, says Tony Daffern, author of Avalanche Safety for Skiers, Climbers & Snowboarders, 2nd Edition, itís important to recognize that some types of terrain pose lower avalanche risk than others. Avalanche terrain is as any area close enough to steep slopes to become part of the track or deposition zone of an avalanche. Terrain features to watch for include the following:
  • Steep straight slopes are obviously potential avalanche slopes.
  • The rounded top to a peak or ridge on a convex slope can be the trigger zone for slab avalanches. The safest path is above the crown line.
  • Concave slopes are safer than convex slopes. When traversing the safe-looking flat bottom part of the slope, watch for soft slab and depth hoar which may not support the snow above if disturbed.
  • Terraces tend to prevent avalanching until later in the season when snow fills them in to form a continuous slope. Early in the season, slides that are retained by the terrace can bury a fallen skier, so use caution.
  • Bowls with rounded concave sides and straight slopes are among the most dangerous terrain traps. Stick to ridges where possible.
  • Steep gullies form natural deposition zones for slab and natural chutes for loose falling snow. There is usually little warning of the avalanche coming and often there is no escape.
  • Wide, gently-angled ridges offer the safest route of travel. Watch for cornices, shelves of unsupported snow.
  • Cirques are amphitheaters ringed by peaks and ridges and can be the scene of extensive slab avalanching, the fracture line traveling rapidly round the whole cirque and releasing large volumes of snow, making escape virtually impossible.
  • Canyons and gorges are natural depositories for avalanching snow. Ask yourself what kind of slopes feed in from above? How much snow is on them and is it stable?
  • Even on flat ground consider the shape and length of runout zones in the event of an avalanche occurring. Keep well away from steep slopes when hazard is high.

Be alert for any signs of previous activity and consider where the debris from an avalanche will end up, says Daffern. This will allow you to avoid potentially dangerous areas or to select a route that reduces avalanche risk to a minimum.

Adapted from Avalanche Safety for Skiers, Climber & Snowboarders, 2nd Edition by Tony Daffern, The Mountaineers Books, $16.95.



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