In 1959, a group of Russian hikers died under mysterious circumstances – and their story, now known as the Dyatlov Pass incident, has intrigued the world ever since. There’s been no shortage of theories about what happened, but none have been able to fully explain all the weird details. Now a new study, backed up by simulations, suggests a snow slab avalanche is responsible.
The Dyatlov Pass (Devil’s Pass) Incident:
In January 1959, a group of nine young hikers — seven men and two women — departed the village of Vizhai on a two-week expedition to Otorten mountain. In the height of winter, the route they were taking had been classified as a Category III, which is the most difficult and riskiest.The hikers trudged through Russia’s snowy Ural Mountains toward a peak locally known as “Dead Mountain.” The hikers pitched their tents at the base of a small slope, as an intensifying blizzard chilled the night air to minus 19 degrees Fahrenheit (minus 25 degrees Celsius). They never made it to their next waypoint.
Only one of the hikers returned: Yuri Yudin, who turned back on the second day due to health issues. When the others failed to return after a few weeks, a search party was sent out to investigate – and they stumbled upon a grisly scene.
Their tent was found pitched on the side of a mountain called Kholat Syakhi. It had been cut open from the inside. None of the hikers were in the tent but their belongings, including their shoes, were. Outside, nine sets of footprints – barefoot or just clad in socks – were found in the snow, leading down to a patch of trees about 1.5 km (0.9 miles) away. And that’s where they found the first bodies.
It took nearly a month for investigators to find all nine bodies scattered amid the snow, trees and ravines of Dead Mountain. Some of the hikers died half-dressed, in just their socks and long underwear. Some had broken bones and cracked skulls; some were missing their eyes; and one young woman had lost her tongue, possibly to hungry wildlife. Their tent, half-buried in the snow and apparently slashed open from the inside, still held some of the hikers’ neatly-folded clothes and half-eaten provisions.
Yuri Doroshenko and Georgiy Krivonischenko were found dead, dressed only in their underwear, near the remains of a small fire. Three other bodies were found between the tree line and the tent, and it was presumed that they had been trying to return to camp.
Medical examinations of these first five hikers revealed that they had all died of hypothermia. Tragic, but perhaps not surprising. However it wasn’t until the remaining four bodies were found, more than two months later, that the mystery deepened.
In a ravine just 246 feet further into the woods, the last four hikers were discovered. Three of them had been killed by serious injuries – one had major damage to his skull, and two others had suffered severe chest trauma. Forensic experts said that the force required to do that kind of damage was like that experienced when being hit by a car, but notably there were no external wounds. The official conclusion was that they’d died as the result of a “compelling natural force.”
But the specifics of the “compelling” force behind the now-infamous “Dyatlov Pass incident” (named for one of the hikers, Igor Dyatlov) have long remained a mystery, and given rise to one of the most enduring conspiracy theories in modern Russian history.
Mystery on the mountain
Plenty of questions have arisen such as…What happened that night? Why did the group leave their tent in such a hurry, and why didn’t they go back for their gear? How did the injuries occur, and why only to some hikers? The story has all the makings of an intriguing mystery, and in the 60 years since it’s attracted its fair share of theories, some of them pretty wild. Everything from natural disasters, to murder or a fight, to secret military experiments and (of course) aliens and yetis, have been blamed.
Following a retired official’s account of the investigation (The Atlantic’s Alec Luhn has summarized some of the most peculiar theories.) But now, a study published Thursday (Jan. 28) in the Nature journal Communications Earth & Environment provides the first scientific evidence behind a much more banal hypothesis: A small avalanche, triggered under unusual conditions, pummeled the hikers as they slept, then forced them to flee their tent into the cold, dark night.
The Dyatlov Pass incident has been the subject of books, movies, documentaries, and podcasts for decades, and now a team of researchers from EPFL and ETH Zurich have put forward a new theory, which seems to explain the injuries.
“We do not claim to have solved the Dyatlov Pass mystery, as no one survived to tell the story,” lead study author Johan Gaume, head of the Snow and Avalanche Simulation Laboratory at the Swiss Federal Institute of Technology in Lausanne, told Live Science. “But we show the plausibility of the avalanche hypothesis [for the first time].”
Right from the beginning of the investigation, an avalanche was suggested as one of the most plausible explanations. But it didn’t quite fit – there was no sign of debris or disturbance to the snow that an avalanche would create, and the hill the group had set up camp on wasn’t steep enough for one to occur. The trigger for the avalanche would have been the group making a cut in the slope to pitch their tent, but there was an unexplained nine-hour delay until the avalanche. And finally, it’s not clear how an avalanche could cause the type of injuries sustained.
The avalanche hypothesis is not new; two federal Russian investigations (completed in 2019 and 2020) also concluded that the hikers were most likely driven from their tents by a slab avalanche — that is, an avalanche that occurs when a slab of snow near the surface breaks away from a deeper layer of snow, and it slides downhill in blocky chunks. However, this hypothesis hasn’t been widely accepted by the public, the new study noted, because neither investigation offered a scientific explanation for some of the incident’s stranger details.
“The slab avalanche theory was criticized due to four main counterarguments,” Gaume said.
First and foremost, there was no sign of an avalanche when rescuers arrived at the campsite 26 days after the hikers went missing. Second, the slope where the hikers built their camp had an incline of less the 30 degrees, which is typically considered the minimum angle for an avalanche to occur, Gaume said. Third, there’s evidence that the hikers fled their tents in the middle of the night, meaning the avalanche was triggered hours after the highest risk event, when the hikers built their camp — a process that involved cutting into the face of the slope to create a flat surface below their tent and a sheer wall of snow next to it (a common practice at the time, the study authors wrote). Finally, some of the hikers had sustained head and chest injuries that avalanches usually don’t cause, Gaume said.
The above is a video of slab avalanches
A ‘brutal force of nature’
In their study, the researchers learned that the angle of the slope near the hiker’s campsite was actually steeper than previous reports indicated; the slope angle measured 28 degrees, compared with the area’s average slope angle of 23 degrees. Subsequent snowfalls in the weeks after the incident could have smoothed this angle, making the slope appear smaller while also covering signs of an avalanche, the team wrote. That detail took care of counter-argument number one.
As for the second, while 30 degrees is considered the standard slope angle at which slab avalanches can occur, this is not a hard rule, the researchers wrote; in fact, there’s evidence of avalanches occurring on slopes with angles as little as 15 degrees. A key factor is the friction value between the upper slab layer (the one that falls) and the base layer (the one that stays in place). The base of the snowpack at the Dyatlov campsite was composed of depth hoar, or “sugar snow” — a type of grainy, crystallized ice that often increases the risk of avalanches, the team wrote. This grainy base layer could have easily helped facilitate a slab avalanche, even at a 28-degree incline.
As for the delay between the hikers cutting into the slope and the avalanche tumbling onto their tents? This could be explained by strong winds that gradually blew more and more snow onto the top of the slope near the team’s campsite. Conditions on the mountain were extremely windy, and snow may have accumulated above the tent for as many as 9.5 to 13.5 hours before the upper slab finally gave way, the team’s models showed.
This leads to the final counterargument: the injuries. Some hikers were found with cracked ribs and skulls — injuries more in line with a car accident than an avalanche. However, the supposed slab avalanche at Dyatlov Pass was far from typical. Rather than standing in the direct path of the avalanche, the hikers would have been lying flat on their backs as they slept, with the snow rushing down on top of them over the small ledge they cut into the slope.
“Dynamic avalanche simulations suggest that even a relatively small slab [of snow] could have led to severe but non-lethal thorax and skull injuries, as reported by the post-mortem examination,” the researchers wrote.
The team’s models showed that, under specific environmental conditions, a slab avalanche could have plausibly toppled onto the Dyatlov group as they slept, long after they cut into the slope to build their camp. The crushing snow all but flattened the tent, cracking bones and forcing the hikers to hastily cut their way out of their snowy sarcophagus, dragging their wounded comrades behind as they attempted to survive the night in the open air. Sadly, none did.
The key, according to the researchers, was a katabatic wind. This kind of airflow is known to rush downhill with some force, gradually depositing more snow uphill from the tent. The researchers simulated the dynamics of a snow-slab avalanche, including how long it could take to break off after a cut in the slope, aided by katabatic winds. They found that the conditions for the avalanche release could be met between 7.5 and 13.5 hours after the cut.
“If they hadn’t made a cut in the slope, nothing would have happened,” says Alexander Puzrin, co-author of the study. “That was the initial trigger, but that alone wouldn’t have been enough. The katabatic wind probably drifted the snow and allowed an extra load to build up slowly. At a certain point, a crack could have formed and propagated, causing the snow slab to release.”
Next, the team simulated the potential damage a snow slab may do to a human body on impact. They found that the simulated snow slab reached a velocity of around 2 m/ (6.6 ft/s) by the time of impact, and at that speed a block of snow with a volume of 0.5 m3 and a density of 400 kg/m3 could have caused injuries consistent with what was recorded. It seems that the victims would have been caught between the falling slab and the compacted snow underneath the tent.
While this paper doesn’t explain every facet of the Dyatlov mystery, it does provide the first scientific proof that at least one popular hypothesis — the avalanche hypothesis — is plausible, the authors concluded. That explanation may be far less exciting than aliens or yetis, but for Gaume, the banality of the avalanche hypothesis reinforces something more important: the human aspect of the catastrophe.
“When [the hikers] decided to go to the forest, they took care of their injured friends — no one was left behind,” Gaume said. “I think it is a great story of courage and friendship in the face of a brutal force of nature.”
“The truth, of course, is that no one really knows what happened that night,” says Puzrin. “But we do provide strong quantitative evidence that the avalanche theory is plausible.”
Either way, we doubt we’ve heard the last conspiratorial podcast on the infamous Dyatlov Pass incident.
The research was published in the journal Communications Earth & Environment. The team describes the work in the video below.