Crevasse Rescue - Introduction
by Tom Kirby
AAI Instructor and Guide
Climbs on large and complex glaciers always entail a risk of crevasse falls. Unlike a fall in rock climbing, where in many cases the fallen climber can simply be lowered to safety, a crevasse fall usually requires the rescuer to work against gravity. And the wet, cold environment in a crevasse imposes the risk of hypothermia, meaning that a rescue needs to happen quickly, even if the climber is uninjured. Crevasse rescue is a mandatory skill for mountaineers – followers and leaders alike – even on the easiest of glaciated routes.
Practicing crevasse rescue on an AAI Alpinism 1 course.
Many manufacturers offer products that purport to take the work out of crevasse rescue, with a combination of slings, pulleys, rope capture devices, and locking carabiners, packaged attractively in a zippered pouch or holster. Most of these products are to be avoided.
Crevasse fall emergencies normally require some amount of improvisation on the part of rescuers. The tools that make you able to respond effectively in a crevasse fall emergency are, first and foremost, your skills, which can be mixed and matched to fit a wide range of situations. Everything else can be improvised from a lean crevasse rescue kit composed of inexpensive, multi-use equipment that climbers normally carry.
AAI Standard Crevasse Rescue Training Scenario
The scenario detailed below is used by most AAI Instructors to teach crevasse rescue in our 3-, 6-, and 12-day introductory mountaineering courses.
Limitations of This Scenario
- This scenario is too "scripted" to use as-is in more than a small fraction of real-life crevasse fall situations.
- The scenario is intended to be used as a supplement to in-person instruction by an AAI guide. There are too many nuances to capture in a written document, and it takes direct instruction and practice to become skilled.
In all AAI instructional courses, we teach several important prerequisite skills before progressing to crevasse rescue. Some of these skills are discussed in blog articles listed below. Study the articles to help lay the groundwork for crevasse rescue instruction in the field.
This scenario assumes that the climbers are in a party of two, roped together and using mountaineers’ coils (not Kiwi coils) to shorten the rope. They are clipped into the rope either with the butterfly knot or the figure eight on a bight, using two locking carabiners on the harness belay loop/tie-in point.
In addition, the climbers in this scenario are using a standard Texas kick prusik system, as taught by most AAI Instructors/Guides. Both climbers have two prusik slings already hitched to the rope connecting them, a long “foot prusik” with two slip-knotted stirrups and a short “waist prusik”, the latter clipped back to the climbers’ tie-in points.
The scenario begins when the mock victim slides off the edge of a simulated crevasse – perhaps a wind-lip or steep snowdrift. If you are using a real crevasse, back up the climbers with a belay.
Arrest the Fall and Build an Anchor
- Assume self-arrest position and straddle the rope so that you are braced directly against the pull of the fallen climber. Kick your feet into the snow.
- Place a piece of snow or ice protection (as appropriate for the conditions) and attach it to a locking carabiner. This locking carabiner will be the master carabiner. Construct the placement carefully; this first piece of protection must be very secure.
- Clip the foot loops of your Texas kick prusik to the master carabiner. Lock the carabiner. Do not open the master carabiner again.
- Reach down and push the prusik as far down the load-bearing strand as you can. Tighten and “set” the prusik hitch. This hitch is now ready to take the weight of the fallen climber; later, it will become the “ratchet” in your hauling system.
- Keeping your ice-axe ready to return to arrest position, slowly allow the victim's body weight to shift onto the prusik sling clipped to the anchor. Look for movement or signs of impending failure (such as cracks in the snow).
Escape the System
- Once you are satisfied that the anchor is solid, you can shift to a kneeling position. Take the rope coils off your shoulder and unbind them. Drop the coils one at a time onto the snow to avoid tangling.
- Make a tether to protect yourself against falling into other hidden crevasses. You will use this tether by tying figure eights and clipping in to them with one of your two tie-in point carabiners, alternating carabiners so as to never be unclipped from the rope. Estimate the distance between the master carabiner and the crevasse lip, add two feet, and tie a figure-eight knot in the rope at this length from the prusik hitch. (If there is a high danger of hidden crevasses in the area, you may want to tie a shorter tether to provide better protection as you move around close to the anchor.) Select one of your two tie-in point carabiners and clear it of all connections. Use it to clip into the new figure eight. Lock the carabiner.
- You are now ready to escape the system. Unclip the other tie-in point carabiner and untie the original tie-in knot. You can now move freely in the radius allowed by your tether. Leave your waist prusik hitched to the rope.
- Take the strand of rope immediately above the prusik (i.e. away from the victim) and tie a figure eight on a bight. Clip this to the master carabiner with a second locker, and lock it. This backs up the prusik hitch, currently holding the full weight of the victim, in case of slippage or failure. Make sure there is about a foot of slack between the prusik and the backup knot, to allow insertion of a pulley later.
- If necessary, back up the anchor. Though not all snow anchors need a backup, it is prudent to build a backup anchor if there is any doubt whatever. Remember to build the backup where it relies on a distinct snow mass, so that it does not compromise the integrity of the first anchor.
Check on the Victim and Prepare for the Rescue
- Back up your tie-in point as added protection against hidden crevasses. Take your pack-prusik or a shoulder-length sling and girth-hitch it to your waist prusik (still tied to the weight-bearing rope). Clip this extension to the unused locking carabiner at the tie-in point on your harness.
- Work your way toward the crevasse lip, probing for hidden crevasses with your ice-axe. You may have to re-tie your safety knot one or more times to reach the crevasse. To the rescuer, the crevasse will often appear simply as a hole, with no clear indication that the “lip” has been reached, the rope having cut deeply into the snow.
- Once you reach the lip, confirm that your partner is conscious and ready to be pulled out of the crevasse. In the best case, she is already close to the lip, having deployed her Texas kick prusik system and ascended the rope. But if she does not answer, you will have to rappel down to see what is wrong and possibly administer first aid. (You can use klemheist knots tied with webbing slings to climb out; or you can use your partner's prusiks, if you are short on slings.)
- Prepare the lip of the crevasse (either to rappel or to raise). First clear excess snow from the edge so that the lip is distinct and firm. Warn your partner before you kick snow down on her. The entire rope should be visible at the lip of the crevasse before you are finished. If you are wearing crampons, use caution not to cut the rope. Once the rope is exposed, pad the track of the rope. Slide your ice-axe, backpack, or trekking poles under the rope at the lip to keep it from cutting in further. If possible, clip the article to the rope so that it cannot fall down into the hole.
Set up a Hauling System
- Choose a hauling method. While there are many possible variations, the simplest scenario entails raising the fallen climber on the strand from which they are hanging, using a 6:1 Z-plus-C pulley system. This system will not work if, for instance, the rope has cut too deeply into the lip, or if there are knots in the rope (“stopper” knots added for safety, for example). But it is the best system for the purposes of our scenario. Construction can be broken into two components.
- The Z-pulley (3:1):
- Unclip from your waist prusik, now on the main weight-bearing rope near the lip, and remove the extension from it. This will now serve as the tractor prusik by which you will apply raising force to the rope. Clip a pulley (or carabiner acting as a pulley) to this tractor prusik. Clip the rope running back to the master carabiner through this pulley.
- Walk back up to the master carabiner, bringing the hauling end of the pulley line with you.
- Clip a second pulley (or carabiner acting as a pulley) into the master carabiner. This is the master pulley. (If you have only one actual pulley device, use it here, where the friction is greatest. The remaining pulleys can be substituted with carabiners.) Take the unloaded section of the load-bearing strand between the prusik and the figure-eight backup knot, and clip it into this pulley. (If there is not enough slack in the line, you can use the same strand on the other side of the backup knot.)
- Untie the figure-eight backup knot next to the pulley. (Leave its locking carabiner where it is for use later.)
- Tighten the pulley line and begin hauling. Make sure you are pulling away from the lip of the crevasse. Haul the victim up approximately one foot to make sure the system is working as planned. If you haven’t done so already, untie your original tie-in knot, situated between the master pulley and the ratchet prusik.
- Note how the ratchet prusik, which was once holding the weight of the climber, has now gone slack and moved closer to the master pulley. As you raise the victim, you will have to pause periodically to slide the ratchet prusik down (closer to the victim) and reset the hitch. You must do this with one hand, while always keeping the other hand glued to the pulley line.
- You can now raise the victim with a mechanical advantage of 3:1. This is adequate for strong rescuers with light victims, but in most cases an additional mechanical advantage will be needed.
- Add a C-Pulley (2:1) to Complete the 6:1 System: To cut in half the force needed to raise the victim on the existing (3:1) pulley system, we only need to add a single pulley to the hauling end.
- Begin by tying the very end of the remaining rope into the anchor. Use a figure-eight on a bight; clip it to the locking carabiner that was recently vacated when you untied the main line backup knot. This will now serve as the back end of the new pulley line.
- Take the hauling end of the 3:1 system – that is, the section of rope on which you would pull to raise the victim – and tie a knot in it (either a clove hitch or a figure eight on a bight will do); clip a pulley (or carabiner acting as a pulley) into this knot.
- Take the line you just anchored to the master point and clip it through the pulley. This becomes your new hauling line.
- You now have a 6:1 mechanical advantage. Though you will raise the victim only one foot for every six feet hauled, the advantage enables almost anyone to rescue his or her climbing partner, no matter how large the weight disparity.
- Make sure that whatever system you devise, the rescuer’s direction of pull is away from the crevasse.
- Check on the victim frequently. As he reaches the lip of the crevasse, the victim may become stuck or need assistance. Do not pull harder without first checking to make sure the victim is not being crushed (a very real possibility, with fatal consequences).
- Make sure the victim's hands do not get caught behind or under the rope as it cuts through the lip.
- Lock all carabiners.
- Once you understand the system, experiment with variations. The Drop-C rescue, executed by another team in the vicinity, is much faster, and will often be the logical choice.
Last, but most important: don't print out these instructions, put them in your pack, and forget about them. Take one of our complete crevasse rescue courses to make sure the skills are ingrained and come to you quickly when it really counts.