Recognizing and Avoiding Avalanche Terrain

This information is simply for research purposes and does not replace the knowledge you will gain by taking an actual Avalanche Safety Course.  It is highly recommended that everybody take an avalanche safety course before heading into the backcountry. You can find courses near you on the AIARE Website or by Googling “avalanche level 1 class”. 

When skiing, snowshoeing, snowmobiling, or doing any other recreational activity in the mountains during winter, it is important to be able to recognize and stay out of avalanche terrain. Usually, avalanche terrain is easily seen by observing the characteristics of the slope. 

That said, before heading out into the backcountry, make sure to read the avalanche forecast


What is avalanche terrain?

Avalanche terrain can be defined as any snow covered slope that is greater than 25 degrees or any terrain that is below a slope that is greater than 25 degrees. 


Determining Avalanche Terrain Based on Previous Events 

Avalanches are very, VERY powerful. When an avalanche occurs in the backcountry, it can completely change the landscape. As backcountry travelers, we can use signs of this to determine where avalanches have happened in the past.  

Signs of avalanches occurring in the past include: 

  • Random spots of no vegetation 
  • Avalanches are known to break large trees and carry them away
  • Trees that only have branches on the downhill side
    • Trees that are not taken down fully from an avalanche will have branches torn off on the uphill side 
    • This is called “flagging”
  • Debris in the run out zone
    • If you see a field of lumpy snow that has tree parts and rocks in it, this is a sure sign that an avalanche occurred above you that carries all of this debris to it’s resting place. 
  • Snow stuck to the uphill side of trees, rocks, or other obstructions

Slope Angles 

It turns out that the slopes most likely to slide are also the slopes that would be the most fun to ski. As said above any slope greater than 25 degrees has the potential to slide. That said, most human triggered avalanches are seen in the 30-45 degree slope angle range.

Why?

Slopes below 30 degrees are unlikely to slide but it is still possible and slopes greater than 45 degrees tend to slide naturally which settles the snow. 

It takes a lot of practice to be able to look at a slope and accurately determine the slope angle. In order to measure it accurately and learn what certain slope angles look like, you will want to get a slope meter. When you are out touring next time, stop every once in a while, lay your pole down on different slopes, and measure the slope angle using your slope meter. By doing this over and over, you will start to develop an eye for slope angles. 

Keep in mind that slope angles are not consistent for an entire slope. Look for any roll overs that have more potential to slide within a slope before skiing it. 


Trigger Points

Trigger points are weak points on a slope where avalanches are likely to start and propagate from. These are caused by anything that interrupts the layering of snow causing the snow pack to be weaker and less cohesive around these objects. 

Examples of trigger points are:

  • Roll overs 
  • Trees not in a forest setting 
  • Buried objects such as rocks 
  • Below rocks or cliffs
  • Below cornices 

Being able to identify trigger points on a slope will help you stay out of potential avalanche terrain and thus stay out of danger. 


Terrain Traps

allison-portillo

The lake in Portillo is a terrain trap.

Terrain traps are anything that can increase the consequence of being caught in an avalanche. Getting caught in an avalanche and getting taken into a terrain trap significantly decreases your chance of survival. Many people think of terrain traps as simply a hole where snow can accumulate on top of you but while these are terrain traps, there are other forms of them as well. 

Terrain traps include: 

  • Gullies
  • Creeks/lakes
  • Cliffs
  • Couloirs 
  • Rocks in the avalanche path 
  • Any place where snow can pile up such as terrain benches
  • Forest/Trees

While some of these terrain traps are places where snow can accumulate on top of you, there are also traps that don’t necessarily bury you but can cause extreme injury, such falling off of a cliff or hitting a tree. 


Where are safe places to travel?

In order to manage your risk in the backcountry, you want to avoid being in avalanche terrain at all times. There are many ways to avoid avalanche terrain in the backcountry including: 

  • Ridges that are not exposed to avalanche terrain above 
  • Dense forest (Trees close together in a forest setting act as anchors and keep the snow pack stable)
  • Far out in a valley where the runout of an avalanche would not reach 
  • Slopes below 25 degrees

Being able to recognize and analyze avalanche terrain to make decisions on where to travel is your second way to reduce risk in the backcountry, behind reading the avalanche forecast

To refresh yourself on more avalanche safety, check out four more avalanche safety articles here!

Have questions? Put them in the comments below and don’t forget to share this with your friends! 


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