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Avalanche Safety

The Safety Site

By Monica Palmer

RSRC Safety Administrator

Recreational Safety takes Responsibility & Control


Due to the recent avalanche at Mount Rose, where a skier lost his life, I am reusing this article from March, 2013.

I believe that most of our RSRC members ski within bounds at our local ski resorts where avalanche prevention usually keeps us safer.  However, some more adventurous skiers may enjoy skiing in the back country where the risk is much higher.  Either way, we all need to be aware of the possibility.

An avalanche is a large volume of snow moving quickly down the side of a mountain. There are three different types of avalanches, loose snow, dry slab, and wet slab, with varying degrees of danger.

A dry slab avalanche occurs when snow slabs on the mountains lose their cohesion due to factors like melting snow or additional snowfall. Both can weigh down the top, hard layer of snow, which then causes the weak, softer snow underneath to give way. The result of this chain reaction is the dry slab avalanche.

A loose snow avalanche tends to be the least dangerous of the three types of avalanches. However, skiers and snowboarders should not disregard them because they still have the potential to cause fatalities.

They are referred to as sluffs or sloughs when small, loose snow avalanches occur when cold, powdery snow on the surface slides down the mountainside. Often occurring due to the snows inability to "hang on" to the slope, it can pick up snow and fan out into an inverted V shape as it moves down the mountain.

It is not uncommon to see many small versions of this type of avalanche, especially in areas where it is very cold and the snow is especially light and powdery. However, even the smallest sluff can turn into a troublesome avalanche if the conditions are right. Often accompanied by a powder "cloud", this type of downhill flow of snow can still take skiers down with it or push them off cliffs or into rocks and trees. Although not the biggest killer of the three avalanches, they still have the potential to be harmful.

A wet slab avalanche is the slowest moving type of avalanche, but can still be extremely dangerous and leave unbelievable destruction behind.

Air and ground temperature, the steepness of the landscape, the type of snow or precipitation falling, and how the snow or precipitation settles on the ground are all factors that determine what type of avalanche can occur.

Wet slab avalanches often happen in the springtime when the air temperature starts to rise and more rain than snow falls changing the overall composition of the snow.

The biggest contributor to the creation of a wet slab avalanche is water. Skiers should be aware as spring approaches and the days begin to get warmer, a perfect scenario for a wet slab avalanche could be in the making. Although slow moving, this type of natural disaster can be very damaging.

The wet, heavy, often rain soaked snow has the power to move boulders, trees, mud, and anything else it its path. When the moving mass finally reaches its destination, it often looks as though it has transformed into a wall of dirt and debris

Do avalanches originate in tree-covered areas?

Good question. Trees definitely alter the snowpack by anchoring snow, intercepting snowfall, intercepting radiation, and by depositing "bombs" and moisture that break up the snowpack.

  1. According to The Avalanche Handbook, avalanches in tree covered areas are infrequent, but they do happen. If you travel in mountainous terrain during the winter, you can rely on very thick tree cover for safety only when there is no avalanche terrain anywhere above the trees.
  2. Avalanches frequently initiate above tree-covered areas and flowing snow travels easily through the trees, even if the trees are thick. Have you ever noticed snow plastered on the uphill side of a tree? This is a good indicator of avalanche activity, and can also be used to determine the height of flowing snow. Remember that forest clearings may be especially dangerous because of instantaneous changes in snow conditions. This means that you can go from safe to unsafe in just a few steps.
  3. Gladed areas are, for all intents and purposes, the same as open slopes. The consequences of taking a ride through the trees are severe. How severe? Think about what might happen if you have a high-velocity encounter with a tree. You can express such an encounter with the following formula: NOTFUN.
  4. You may not be safer in forested areas, and if conditions are very poor, you might actually be less safe. As always, you must use the current terrain, weather, and snowpack to determine the likelihood of avalanche formation, and you must choose terrain appropriate for conditions.
  5. According to researchers, people in North America are much more likely to suffer traumatic injuries during avalanches than their counterparts in Europe. Trees are definitely a contributory factor.
  6. Don't forget about tree wells.


Skiers/Snowboarders Guide to Avalanche Safety

Each person in your group should wear an avalanche beacon and know how to use it.

Probes used in conjunction with beacons, can be extremely helpful in locating a buried skier.  Remember a beacon will be of little help without a shovel. Be sure you carry a shovel as part of your gear.  First and foremost, practice using your beacon. Time is of the essence in an avalanche rescue. The average victim has less than 30 minutes to be recovered alive. This means finding the victim and then digging through the snow to recover the victim.


Much of this information came from, with permission to share.