The Z-Pulley Crevasse Rescue System

By Mary Gianotti

[NOTE:  Pictures will be added to this post when they are available.]

One of the main safety hazards in crossing the Juneau Icefield is that posed by snow-covered crevasses.  Crevasses are cracks in the surface of a glacier caused by stress from moving ice, and vary in depths up to many tens of meters.   They often occur at the edges and lower extents of glacier, at the outside of bends, and areas where the glacier surface steepens.  Given that even the safest route takes us through some crevassed regions, JIRP field parties rope up into groups of four or five team members and move in unison.  In the event that a team member falls into a crevasse (which has rarely happened on the icefield!), JIRP trains students to implement the Z-pulley system. This system uses a simple set of tools: a climbing rope, a few loops of cord or webbing (called slings), sit harnesses, and a small number of carabiners.  Additionally, skis and ice axes are used to build a safe anchor, which can be used to haul the team member to safety.  The system is efficient and lightweight.

To simulate a rope-team member falling through the snow into a crevasse, we took turns dropping off of the moat’s lip.  Immediately, all other group members dropped into the self arrest position, securing themselves to the snow with their ice axes and bodies to stop the fall. The first order of business is to communicate with the victim: Are they alright? Do they need medical attention? Can they climb out by themselves, or should we build a Z-pulley system?

After establishing the physical state of the victim and determining that they need assistance, the next task for those up on the surface is to build an anchor.  A couple members hold the weight of the victim; this frees another member or two to begin digging an anchor. Fortunately, Alaskan snow is almost always wet, thanks to the wonderful rainforest climate of the region.  It therefore provides a secure hold for the anchor: usually a pair of skis, clove hitched together by a sling and buried.

Once the anchor is completed, the rope is connected to the anchor using a sling, into which a special, friction-generating knot known as the “prussik” is tied.  This sling is then clipped into the anchor with a carabiner.  After this is accomplished, the weight of the victim can be safely shifted to the anchor.  Other  team members can also clip into this anchor, either directly or by securing themselves to the climbing rope via another prussik.  This allows the rescuers freedom to safely move about, check on the victim, and, if possible, prepare the lip of the crevasse (by knocking off snow, if safe, or putting an object under the rope so that it doesn’t cut deeply into the snow). Ideally, a team member stays at the crevasse’s lip to monitor the victim.

Now it is time for the rest of the members to set up the Z-pulley. The system is named this because the rope is folded back onto itself like the letter “Z” using additional prussiks and carabiners.  This arrangement provides a 3:1 multiplier in force – thus making rescue of the victim possible.

We first built the Z-pulley in one of the biuldings, then outside in the sunshine, and then in an icy rainfall that was blowing sideways. Students practiced being at all positions of the rope line.  We all lead the team at one point or another. We worked through nearly every possible  scenario until we came up with a solution. “Mr. Backpack” and other inanimate objects were great at being non-responsive dead weights.  Sometimes, unknown to the pull team above, the weight of one person in the moat secretly became that of three, as others joined in to challenge the haulers and test the system.

So as of now, we feel ready to conquer any crevasse that dares to cross our path.  I know now that crevasse rescue is an important tool for glacier travel. On our traverse from C-17 to C-10, there were times when we had to travel in rope teams over crevassed terrain and we crossed the areas with confidence and security.  While there were lighter moments in our training, I trust my fellow expedition members to realize the gravity and weight of the situation if I fall into a crevasse and that they will pull me to safety.