After three days of sunny weather, I, Jacob Weintraub (24), and my partner, Randy Lee (37), had finished a double carry beyond the icefall at the end of the Northeast Fork of the Kahiltna Glacier. We camped at the base of the West Rib route.

On May 9, we planned to carry our first load up the Chicken Couloir and place a cache at our proposed campsite at 12,900 feet. The couloir is about 1,200 feet long and 50°–55° snow and ice, starting at 11,000 feet. The previous night it had lightly snowed, with three inches of light powder at our camp near the base of the couloir. Winds were observed up to 30 mph from the southwest at 14 camp on the nearby West Buttress route, while at our well-protected campsite the winds were light and variable. On the morning of May 9, it was cloudy with good visibility, light winds, and around 0°F ambient temperature at camp.

We set out with 60-pound loads and booted our way through thick snow (8–12 inches deep) to the top of the couloir over the course of four hours. The snow formed a solid, seemingly homogeneous layer over a layer of ice that was weak and wouldn’t hold a screw. We placed running protection (snow pickets or deadman anchors) at one piece per rope length. By 4 p.m. we made it nearly to the top of the couloir, but we were still below the ridgeline of the West Rib. There was another 700 feet of elevation to gain before we reached our proposed cache.

After a break, I set out to gain the ridge. We had observed no avalanche warning signs up until that point. The cloud cover was consistent, and there were no propagating cracks, whumpfing, or settling in the snowpack. At this point, the couloir was about 30 feet wide and the steepness had lessened to around 40°. No more than a dozen steps after restarting, I heard a loud “thwoomp” noise, and 10 feet above me, a layer of snow broke and started to slide. The slab was about six inches thick and maybe 10 feet wide. I was unable to anchor myself with my tools, and the snow picket we buried as a deadman failed and ripped from the slope. We both tumbled the entire way down the couloir, stopping about 50 feet past the bergschrund at the base of the couloir. Another 50 feet and we would have been in an open crevasse field. Neither of us was buried in the debris.

After reorienting ourselves and checking for major injuries, we limped and crawled to our tent. It was no more than 200 feet from the base of the couloir. It was clear that we were unable to continue with our expedition. I radioed for evacuation and we were picked up in the hour by the National Park Service. I dislocated my shoulder and tore my labrum. Randy suffered an open fracture of his arm and heavily bruised his pelvis.

ANALYSIS
We did observe a debris cone at the base of the couloir, but the debris did not look new. We also felt a single whumph as we walked up the cone, but above the bergschrund everything felt very stable.

I wish that I had more knowledge about avalanches because I would then be able to better critique my decision-making. Perhaps someone with more knowledge would recognize the loose bond between the snowpack and the ice below or have some other intuition to inform them. (Source: Jacob Weintraub.)

Editor’s Note from Pete Takeda: I once deliberately triggered a similar avalanche in the Andes. After many days of generally clear weather, my partner and I were descending a snow face from the 5,000-meter level. A blizzard of light snow had started two hours earlier. The accumulation was rapid. I downclimbed a wide snowfield angled at 60° with an overhead belay. There were eight to 10 inches of fluffy snow over a consolidated snowpack. I cut a wheel of snow several feet in diameter with my ice tool and slid it down the slope. (I figured that if the snow above me cut loose, I could stay afloat with an overhead belay.) The wheel created a point release that rapidly widened until it cut a path several hundred feet wide. It cleared the face below of all accumulated snow and we descended safely, though not without other incidents. The takeaway is that even light, fluffy snow, set at the right angle, can retain enough cohesion to consolidate and slide dramatically.