Education

Education

Photo: Dean Cummings giving a presentation during Avalaunch at Outdoor Retailer Winter Market.

What Causes Avalanches?

Avalanches are usually caused by a weak layer of snow within the snowpack. This is often the result of a fresh snowfall that has not bonded well with the pre-existing layer of snow beneath of it.

This means that the new snow slab can easily slide off of the layer underneath of it and when this happens; you will see an avalanche.

Weak layers can be caused by many different events. Weak layers can form in December and last throughout the season, so don’t assume that a lack of snowfall will always mean low avalanche conditions

  • When you dig a pit to examine the snowpack, try to choose a spot with the same aspect, orientation and sunlight exposure as the slope you will be skiing down. Look for weak layers and layers of surface hoar. Learn how to test the snowpack for stability by using a shovel compression test.
  • If you need to travel across an avalanche prone slope; do this 1 person at a time. If an avalanche does occur, you will have several people looking for 1 person – rather than have 1 person looking for several people.
  • Always wear an avalanche beacon when you are traveling in avalanche territory. Be sure to carry a shovel and probe as well. Make sure you know how to use all of this safety equipment and make sure it is easily accessible in your pack. Avoid bringing anyone into an avalanche danger zone with you that doesn’t have ALL of this equipment.
  • Concave slopes are safer than convex slopes. A convex slope curves like a dome and is highest in the middle. A concave slope is shaped more like a bowl. The natural force of gravity on a concave slope can help to hold a snow slab in place.
  • Most people who die in avalanches do not die from carbon monoxide poisoning or asphyxiation. The majority of these unfortunate skiers and riders die from trauma and internal injuries that are sustained while being swept down the slope by an avalanche. Consider this when judging the avalanche danger of a particular slope. Ask yourself what will happen to you if there is an avalanche? Will you be swept down a rock-free 35 degree pitch, or will you be sent through a series of pine trees, rock gardens, and then off of a 200 foot cliff?
  • Trees can help to make a slope safer by holding the snowpack in place. If there is an avalanche, it is less likely to grow and become devastating. Don’t take this advice in an absolute fashion; you can still have a deadly avalanche on a slope that has trees scattered heavily. However, the presence of trees rather than an avalanche slide path can also hint that a slope may be relatively safe. Look for pine trees that have low branches running through the weak snow layers; these are what can help to stabilize the slope. Bare trees with little or no fauna will not significantly decrease the avalanche risk of a slope.
  • Choose your route up the mountain just as carefully as you choose your route down. Your exposure to the slope will be even longer on the way up and the danger of avalanches should be a priority in your ascent choice.
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