The Crackulator

A system to help glacier skiers avoid crevasse falls.

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Background Notes: Why Simplify Complex Problems?

Most accidents in the mountains, like being caught in an avalanche or falling in a crevasse, result from multiple interacting factors. For this reason, some criticize avalanche decision making aids for what they see as oversimplifying a complex problem. Nevertheless, we can only begin to understand complex events by first simplifying them. This is the underlying basis of instruction and learning at any level: you start simple and build knowledge from there. Similarly, using a select subset of variables is a time-tested and effective way to begin understanding complex situations.

Some principles capture the essence of simplifying and its relevance to real-world events. For example, the Pareto Principle says that most results are explained by a small number of causes. Pareto estimated that, for many events, roughly 80% of the effects come from 20% of the causes. For example, 80% of work is completed by 20% of the employees. In the context of crevasses, Pareto would suggest that most crevasse falls could be explained by a small number of variables.

Another principle, Occam’s Razor, says that the simplest or most obvious explanation should be preferred. That is, start with the fewest variables that you believe are most important and only later add more variables if they significantly improve predictions. In the outdoor industry, this rule is better known as Keep It Simple Stupid, or KISS.

Simplifying is an effective strategy for teaching and predicting the likelihood of events such as avalanche accidents. Checklists, like the Avaluator, are used extensively in medicine and aviation and have saved many lives.

Countless studies have shown that even simple decision-making aids and checklists can engage the logical brain and can produce dramatically better decisions. And even among highly skilled people, a checklist can help “prime” us for conditions we might encounter in the task at hand.
— Bruce Tremper, Avalanche Essentials


Background Notes: From Rules to Knowledge

Aspiring ski mountaineers need a basis of rules to start building experience. In the complex mountain environment, we first teach the fundamental rules, such as in a level-one avalanche course or six-day mountaineering course. Students can then practice these rules and gain experience. With experience they gain judgment and can make better decisions than by using the rules alone.

Teaching the intricacies of avalanche hazard analysis has always involved an essential conundrum—how to impart enough usable information to the students so that they can get out and gain some experience without getting in trouble.
— Mary Clayton, Canadian Avalanche Center News

Ski mountaineering brings together several big skill sets: skiing, backcountry skiing, avalanche avoidance and mountaineering. Some of these skills can be learned with basic instruction and practice that includes trial and error. However, neither avalanche or crevasse fall avoidance can be learned effectively by trial and error because the environment often provides no feedback from bad decisions. And if you do get feedback from a bad decision, it may be fatal. For this reason, it is critical that novice glacier skiers are provided with some basic rules that, if applied, will minimize their risk as they gain more experience. The Crackulator could become a component of such training.  


Background Notes: More information on factors affecting crevasse fall potential

Glacier Factors

+5 Are there both crevasse and avalanche danger? You may survive an avalanche, and you may survive a crevasse fall, but you probably won’t survive being avalanched into a crevasse.

+5 Would holding a fall be questionable? Holding a fall can be difficult if: The glacier surface is icy or steep. The crevasses are so big that multiple people could be on a single bridge. The rope team is only two members. There is a weight imbalance among teammates.

+4 Is the light flat or visibility reduced? Flat light can hide a crevasse just beyond your ski tips.

+3 Is the snow soft? Soft snow—hand hardness of 4 fingers to fist—creates less supportive bridges. Soft snow can be new precipitation snow, drifted snow, or old soft snow.  

+2 Is the snow less than two meters deep? Thinner snow cover means thin and weak—made of faceted snow crystals—crevasse bridges.

+1 Are there known or visible crevasses? While visible crevasses do indicate danger, the crevasses you can’t see are a bigger problem.

Skier Factors

+5 Are you in doubt? More caution is necessary if you are unsure of the crevasse danger.

+4 Have you spent 10 days or fewer on a glacier? If you’re new to glaciers, then you need to use more caution.

+3 Are you skiing uphill? This is where you’re most at risk because of increased exposure time, you may be track-setting on untouched snow and you exert more pressure on the snowpack than when skiing downhill.

+2 Is the glacier unfamiliar? Just like a new snowpack should be considered guilty until proven innocent, an unfamiliar glacier should be considered suspect and approached with more caution. Familiarity with a glacier, especially that gained by visiting in summer, helps you know what underlies the blanket of seasonal snow.

+1 Are you a beginner or intermediate skier? Lower-ability skiers are less able to stop before a crevasse, less able to hold a fall and exert more impact on crevasse bridges while turning and crashing.

+1 Are you tired? Fatigue and hunger contribute to poor decision making.


Background Notes: More information on Recommended Actions

Normal Caution

Normal caution does not mean you are safe, just less likely to fall in a crevasse. All glaciers present some crevasse fall danger to skiers. Follow these recommendations when skiing on any glacier, regardless of your ability or what seems to be low danger.

  1. Take a glacier travel course. Learn glacier travel skills from an AMGA-certified ski or alpine guide.

  2. Practice rescue. Have your rescue system dialed. Practice: 1) building snow anchors, 2) self rescue by ascending the rope, 3) rescuing an unroped companion and 4) haul systems.

  3. Wear your harness.

  4. Spread out. Stay a ski length apart to avoid standing on the same crevasse bridge.

  5. Consider roping together. Particularly if in doubt or when skiing uphill. On the ascent, when the group is going slow, roping together does not create additional hazards as it does on the descent.

  6. Manage the rope. Choose an appropriate spacing between skiers to minimize slack. Take up slack with a prusik or mechanical rope grab. Consider using stopper knots to catch on the crevasse lip.

  7. Bring rescue gear. Have 2 ropes carried by separate people in case a rope-carrier falls in a crevasse, 1-2 ice screws each, biners, prusiks or rope grab and cordelette.

  8. Always keep one ski on. Skis will distribute weight during breaks and while putting on and removing skins.

Extra Caution

These are conditions that require extra caution but do not appear dangerous enough to warrant no-go. Extra caution is where the most uncertainty lies, and therefore presents the most difficult decision making.

  1. Apply all of the recommendations for normal caution.

  2. Rope together when skiing uphill. If you choose to ski uphill unroped, have a legitimate reason not to, such as if roping together increases exposure time below a serac. Consider staying roped when skiing downhill.

  3. Measure snow depth and bridge thickness with your probe. Upon arrival on an unfamiliar glacier, start your tour with your probe in hand to measure snow depth and bridge thickness.

  4. Consider turning back.

Not Recommended

Dangerous conditions. Due to the small margin for error, backcountry travel in these conditions requires hundreds of days of glacier skiing experience.

  1. Have no-go or turning back as your number one option.

  2. Find an alternate route.

  3. Rope together on both uphill on downhill. Use stopper knots to help catch a fall.



Many thanks to those who have helped with this project over the years: Kathy Cosley, Nate Furman, Mark Houston, Eric Larson, Cecelia Mortenson, Kirsten Cohen, Mark Smiley, Dave Stock, Molly Stock and Heather Thamm.