Fundamentals: Crossing a Crevasse Field

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By Don Graydon.

Climbers have a number of ways to get safely across a field of crevasses. The techniques described here are typical, but you?ll have to adapt them as needed in the field. Routefinding on a glacier involves finding a path around or over all the crevasses that you see, guarding all the time against hidden crevasses. The crossing is seldom without its detours as you carefully pick your way over the glacier.

The End Run

Crossing directly over a crevasse is seldom a preferred choice. Where a crevasse pinches down in width, often near its end, the safest and most dependable technique is to go around it, in an end run.

In late summer when the winter snow has melted down to the ice, you may be able to see the true end of the crevasse. But if seasonal snows still blanket the glacier, the visible end of the crack may not be its true end. Make a wide swing around the corner, probing carefully. Look closely at adjacent crevasses to judge whether one of them could be an extension of your crevasse; you could actually be crossing a snow bridge.

Snow Bridges

If an end run is impractical, the next choice is to cross a snow bridge. Deep winter snow hardened by wind can develop into a crevasse bridge that lasts into the summer climbing season. Other, sturdier bridges are really thin isthmuses between two crevasses, with foundations that extend deep into the body of the glacier.

Study a bridge carefully?try for a side view?before putting any faith in it. If you?re in doubt, the leader can go in to probe and get a close-up look while the second climber stays braced against the taut rope to help guard against a possible breakthrough. After the leader gets across, the rest of the party follows exactly in the leader?s steps, also receiving a degree of protection from a taut rope held by a braced climber.

The strength of a snow bridge varies tremendously with temperature. An arch that might support a truck in the cold of winter or early morning may collapse under its own weight during an afternoon thaw. Cross every bridge with caution every time. Don?t assume that because it held in the morning during the ascent that it?s safe as you head down in the afternoon.

Jumping

Jumping is one of the least common tactics for crossing a crevasse. Most jumps across crevasses are short, simple leaps. If you?re planning a desperate lunge, be sure you?ve ruled out all the alternatives and see that you are well belayed.

While being well supported by a taut rope or belayed, probe to find the true edge of the crevasse. If you need a running start for the jump, tramp down the snow for better footing. As final preparation, put on parka, mittens, and hat, check prusiks and harness, and spool out the amount of rope slack needed from the belayer. Then jump?with your ice ax in the self-arrest position, ready to help you claw over the edge if you?re shy of a clean landing.

With the rope now linked to the landing side, the other climbers have a less dangerous jump ahead. The belay rope can help pull up on any jumper who falls just short of the target.

Into the Crevasse

On rare occasions, it may be practical to get to the other side of a shallow crevasse by climbing into the crevasse, crossing it at the bottom, and climbing out the other side. This tactic should be attempted only by a strong, highly trained, and well-equipped party that is ready to provide a good belay, plus assistance in case the crevasse bottom collapses and leaves the climber hanging. One further caution: often, what appears to be a solid bottom isn?t.

Echelon Formation

Certain crevasse patterns preclude the rule of keeping the rope at right angles to the crevasses. If the route demands travel that is parallel to crevasses, the echelon formation can sometimes help. This formation is safest on stable, heavily crevassed glaciers where location of the crevasses is known and the risk of hidden holes is small. The formation offers an alternative to following in the leader?s footsteps through a maze of crevasses where single-file travel is impractical. Avoid moving in echelon where hidden crevasses are likely.