The researchers modeled how these winds could have accumulated snow above the tent and how long it would take to reach a critical load that would cause the upper slab to slip off the weaker layer below, now that its structural integrity has been compromised by the cut. “That was how the load increased,” says Gaume. “Because there was no other way – there was no snowfall that night.” Sometime after midnight, enough weight had accumulated over the weak layer that suddenly collapsed, sending the slab to the tent. It would have been a relatively small avalanche – perhaps 5 meters by 5 meters – that the researchers simulated with inspiration from the Disney snow model. It would have been enough to fill the hole that the campers dug in the snow, but not enough that the rescue team could find clear signs of an avalanche 26 days later.
Here we see the disturbance caused not by an imaginary snowman, but by the combination of the cut above the tent and the snow deposited by the wind.
Video: Guame et al.An avalanche need not be large, however, to cause serious damage to the human body. Usually, walkers who are caught in one tend to just suffocate. But in this case, none of the nine victims died of asphyxiation and some suffered severe trauma to the chest and head.
This can also be explained by the dynamics of the avalanche of slabs and the descending winds. Although it was not snowing at the time of the incident, the catabatic winds would have produced a much more dangerous type of deposit above the tent. “The wind was eroding and carrying the snow, which was made up of very small crystals,” says Gaume. “And then, when he deposits, [the crystals] are highly compressed. This could have created a dense layer of snow that weighed perhaps 25 pounds per cubic foot. And even more unfortunate for our adventurers, they put their skis on the ground for their tent, creating a hard substrate for the snow to crush them.
Gaume and Puzrin went even further, modeling how this trauma could be. To calibrate the simulation, they used data from old automotive industry crash tests made with human corpses, instead of dummies. (To be fair, it was the 1970s, which was a … different time.) They then modeled the release of simulated snow blocks of different sizes on a digital model of a human body and compared it to the results of the collision. “What we saw is that it would not be fatal, but it would create moderate to severe injuries,” says Gaume. (Below, you can see the damage that a meter-long piece of snow can cause.)
As the snow deposited by the wind would be very dense, even a small avalanche could have caused serious injuries to campers in the tent.
Video: Guame et al.From this, they concluded that the climbers survived the initial crushing of snow, making their way out of the tent, although some of them were seriously injured. But if they had escaped a relatively small avalanche, why would they run more than eight hundred meters away, instead of standing around to dig up their supplies, especially their boots? The investigators found that the group had stored another set of supplies in the forest, so perhaps they had gone out to fetch them in a panic. “You start to cut the tent inside to get out,” says Gaume. “You see that there was an avalanche, and then you may be afraid of an second avalanche. And then they may have decided that the best option would probably be to go to the forest, build a fire and try to find the supply. ”