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Feature - Sometimes, knowledge isn’t enough
What makes snow slide has been studied by scientists and mountain guides for years, but we’re still a long way from understanding avalanches
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Whatever the precipitating event was, what happened next still leaves Eric misty-eyed and a bit numb whenever he talks about it. According to Bruce Allen’s technical report, commissioned by the B.C. Coroners Service, the avalanche ran down a wind-loaded gully on the northwest aspect of Cheops below the cornice. In addition to being in the lee of the prevailing winds, the gully was also cross-loaded from the west. The snow fractured for a distance of 100 metres. Additional fracture lines propagated diagonally – and into the deeper instabilities – down the ridge to the west of the gully for another 183 metres. Average depth of the fracture was 2 metres.
Picking up speed and volume, the snow stepped down to the ice layer of November. Seconds after hearing a loud "crack", Rich Marshall was on his feet yelling to the students below, "AVALANCHE! AVALANCHE! AVALANCHE!" By the time most of them spotted it, the air blast was already hitting them. They didn’t have a chance.
Bruce Allen measured the distance from the highest fracture line to the runout on the valley floor at about 800 metres, eight-tenths of a kilometre. The incline – 45º more or less – didn’t appreciably decrease until the base of Cheops met the valley below.
The wall of snow hit the valley floor at nearly 180 kilometres per hour.
The top of the avalanche (west end) filled the valley floor and ran some 40 metres up the other side of the slope into the trees at the bottom of Hospital Gully, leaving a deposition of two metres. Snow carried on the wind blast dusted Rich and Abby still higher upslope. The volume of snow sliding off Cheops and the momentum was great enough that the centre of the avalanche ran up the opposite side of the valley and turned down valley where it ran another 400 metres before coming to a silent stop.
The total deposit in Connaught Creek Valley was 740 metres long and averaged 85 metres wide. Average depth was 2.5 metres and maximum depth, 5 metres.
There’s no way to know how many people would have died had Rich and Abby not stopped for tea when they did. Chances are pretty good the toll would have been much greater than it eventually was since they managed to methodically dig out five students.
That’s because the two of them were trained mountain guides. They’d done the study, gained the experience, knew the drill. They’d bridged the gap between knowledge and application. And this was most certainly application.
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