62 years ago, a ski expedition set out on a remote mountain in the Urals – and never returned. Only their bodies were found. Since then, authorities and scientists have been puzzling over what happened to these nine people. Now researchers may have solved the mysterious case of the Dyatlov Pass accident. Accordingly, a fatal combination of natural and man-made causes was to blame.
On January 27, 1959, a group of ten scientists and students set out on a 14-day expedition to Mount Gora Otorten, a remote peak in the north of the Ural Mountains. Although all participants were experienced skiers and tourers, this wintry tour with temperatures as low as minus 30 degrees was an enormous challenge. So it’s no wonder that one of the participants preferred to turn back after a day – luckily. Because the remaining nine expedition members should not return alive.
Violent death with unknown cause
That something was wrong with the expedition only became apparent when the group did not show up at their starting point several days after their planned return. A rescue team was then sent out, and found what they were looking for on February 26th: On the slope of Cholat Sjachl, translated as “Mountain of Death”, a good 20 kilometers from the expedition’s destination, they first came across the severely damaged tent and the group’s equipment. A little later they also found the bodies of the nine participants in the expedition. Two of them were only wearing underwear, and a few others had severe injuries such as fractures to the skull and chest.
What happened? After the bodies and remains were recovered, the Soviet authorities investigated the cause of the accident, but stopped the investigation after three months. In their report they only came to the conclusion that a “massive force of nature” must have led to the death of the expedition members. But at that time they could not reconstruct what it was about and what had happened in detail at the Djatlow Pass. To this day there are countless myths and hypotheses about the cause of death of the nine people – the range of legends ranges from murderous yetis to secret military experiments.
Was it an avalanche?
Two Swiss geo-engineers and avalanche experts have now taken up this mysterious “cold case”. Johan Gaume from the Polytechnic University of Lausanne (EPFL) and his colleague Alexander Puzrin from ETH Zurich combed through Russian archives for the documents on this case, spoke to specialist colleagues and then developed an analytical-numerical model based on the data. With this they reconstructed the conditions and events on the last day of the expedition.
At the top of the list of causes was an avalanche accident. This was supported by the fact that the nine participants in the expedition had made their night camp on a snow-covered mountain slope. However, there were some observations that at first glance were difficult to reconcile with a classic avalanche: With a slope of only around 23 degrees, the slope above the camp was actually too flat and there were no clear traces of a larger avalanche. In addition, the chest and skull injuries found on some corpses were untypical for such an event. Also strange: if there was an avalanche, it could only have gone off several hours after the tent was pitched. “The earlier investigations could not explain how an avalanche can be triggered in the middle of the night if it did not snow the night before,” says Gaume.
Pit, winch and a slab
Is the avalanche scenario wrong after all? Gaume and Puzrin say no. Because their models show that there is one type of avalanche that suits the unusual circumstances on site. This is a slab avalanche – a type of avalanche in which the upper part of the snow cover remains almost intact and slides down as a whole on an underlying weak zone. Unlike dust avalanches, such slabs can come loose even on a slight slope. In addition: “Using computer simulations, we show that a slab avalanche can cause injuries similar to those found on some of the dead,” says Gaume.
The slab avalanche at the Djatlow Pass was most likely triggered by a combination of man-made and natural causes. Because the finds at the scene of the accident indicate that the expedition members dug a pit in the snow cover of the mountain slope in order to better protect their tent against the wind. “If they hadn’t cut the slope, nothing would have happened,” says Puzrin. “That was the initial trigger, but it would not have been enough on its own.” In addition, there was a special fall wind that blew down the slope: “These katabatic winds probably carried the snow, which slowly piled up,” explains the researcher.
As a result, a thick, heavy mass of snow gathered above the tent, unnoticed by the sleeping group. A few hours later the snow cover gave way under this load and the slab of snow came off. The masses of snow then raced over the tent as a compact mass and hit the sleepers with enormous force – enough to fatally injure some of them and spill the others. If this scenario applies, Gaume and Puzrin would have solved the riddle of the disaster at the Djatlov Pass. However, they also emphasize that this disaster remains largely a mystery: “The fact is that nobody really knows what happened that night. But we have strong quantitative evidence to back up the avalanche theory, ”says Puzrin.
Sources: Swiss Federal Institute of Technology Zurich, Ecole Polytechnique Fédérale de Lausanne; Technical article: Communications Earth and Environment, doi: 10.1038 / s43247-020-00081-8