The mysterious deaths of nine Russian hikers more than 60 years ago have defied explanation and inspired conspiracy theories for decades, because of the puzzling condition of the bodies—scattered, with severe injuries, and some were unclothed—and the absence of a clear-cut cause of death. Now, a pair of scientists based in Switzerland have presented video evidence collected onsite that bolsters the idea that the tragedy, known as the Dyatlov Pass incident, occurred due to a slab avalanche, which is a special type of deadly snowslide that can strike on low-angled slopes.

Alexander Puzrin, a professor of geotechnical engineering at ETH Zurich, and Johan Gaume, head of the Snow and Avalanche Simulation Laboratory at Ecole Polytechnique Fédérale de Lausanne, first pinpointed a slab avalanche as the potential cause of the deaths in a study published in 2021. The intense media coverage of that research, combined with equally passionate pushback from skeptics—some of whom did not believe such avalanches occurred on the Pass—inspired the researchers to follow up on their hypothesis with trips to Dyatlov Pass, which is named after Igor Dyatlov, the lead mountaineer that died on the route. The latest of these trips took place just two months ago, in dangerous conditions similar to those the night of the incident, and resulted in the first video evidence of recent slab avalanches on the Pass.“In the year since publication of our article, we helped them to organize three successful expeditions to the Dyatlov Pass,” Puzrin and Gaume said in a study published on Thursday in Communications Earth & Environment. “The direct evidence from the Dyatlov Pass area obtained in those expeditions confirms that the region is avalanche prone and that slopes above the location where Igor Dyatlov and his group pitched their tent are steep enough for avalanches to release,” the team continued. “Independent research by Russian snow and climate scientists supported assumptions and the main results of our slab avalanche modeling.”The new research demonstrates that slab avalanches occur in the same region and under similar weather conditions to those experienced by Dyatlov and his companions on that fatal night of February 1, 1959. Though avalanches have long been discussed as a possible cause of death for the group, questions have been raised about the odd injuries on the bodies, which did not neatly fit with typical avalanche trauma, the shallowness of the slope where they died, and the lack of any sign of snow-slides by the rescuers who discovered the bodies.Indeed, much of the fascination with the Dyatlov Pass incident stems from the weird state of the group’s remains, which were found in various locations downslope from where they had pitched their tent. Four of the hikers had severe chest or skull injuries, two were missing eyes, one had lost a tongue, and some were naked. The eerie nature of the corpses has led to their deaths being variously attributed to “an infrasound-induced panic, animals, attacks by Yetis or local tribesmen, katabatic winds, a snow avalanche, a romantic dispute, KGB/CIA secret activities, ballistic rockets, or nuclear weapons tests,” according to the new study.In their 2021 study, Puzrin and Gaume argued that slab avalanches could provide an answer to the mystery while satisfying most of the oddities surrounding the deaths. Slab avalanches happen when a slab-like layer of snow is positioned on top of a weaker layer, creating dangerously pent-up pressure that can be released by a relatively small trigger. The researchers suggested that the pitching of the tent might have set off a fatal chain of events that eventually led to a slab falling on the sleeping hikers, causing severe trauma in some of them, and prompting the rest to run into the night without proper gear, where they ultimately succumbed to the cold.In addition to the recent video evidence, the new study presents results from expeditions in the winter and summer of 2021 that counters claims that the slopes of Dyatlov Pass are not angled enough for avalanches. The summer trip revealed that the terrain is covered in natural steplike drops, on meter scales, that could produce a slab avalanche, even though the broader slope appears deceptively safe under snow cover. These hidden features may have contributed to the experienced group’s false sense of security in their camp location. “The steps have inclinations exceeding 28 degrees, and many slopes are even steeper than 30 degrees,” notes the study. “What’s more, these slopes are not just local, they are continuous: no matter where you pitch your tent you are likely to be below one of them.”The 2021 winter expedition also produced tantalizing hints of slab avalanches just a few miles from Dyatlov Pass, prompting Puzrin and Gaume to organize a third expedition.“On the 28th of January 2022, exactly 63 years after the Dyatlov group was seen alive for the last time, two professional mountain guides from Ekaterinburg, Oleg Demyanenko and Dmitriy Borisov, left for the Dyatlov Pass on two snowmobiles,” said the researchers in the study. “The initially favorable weather conditions quickly deteriorated, with wind and temperatures becoming similar to those on the night of the 1959 tragedy.” “Several times, the 300-kg snowmobiles and their drivers were overturned by wind gusts,” they added. “Visibility became extremely poor. And then, when after a few failed attempts the two mountain guides approached their destination, the visibility briefly improved and revealed traces of two snow slab avalanches.”Demyanenko and Borisov documented the remains of these avalanches and observed them vanishing under the snowfall within about an hour of their discovery.“No wonder then that the Dyatlov rescue team could not find signs of an avalanche 3 weeks after the incident,” noted Puzrin and Gaume. “This also explains why no avalanches have been observed there before: in such severe weather conditions the Pass cannot be easily accessed by hikers, while traces of small slab avalanches disappear within a few hours.”The new research corroborates the team’s previously published models and offers a robust account of the horrible events that befell Dyatlov and his companions all those decades ago. Though Puzrin and Gaume stop short of claiming that the mystery has been solved, they end their study with a sphinxlike sentiment befitting of the eerie tragedy at Dyatlov Pass that has captivated so many people.“Time and again, we were asked whether our article brings to an end our work on the case,” the pair concluded in the study. “We always responded that, although the case itself remains open, our part is closed: we did not want to spend the rest of our lives trying to solve the Dyatlov Pass mystery. One year later, we are no longer so sure. If someone asks, we will refrain from an answer.”