Has science solved one of history’s greatest adventure mysteries?

The bizarre deaths of hikers at Russia's Dyatlov Pass have inspired countless conspiracy theories, but the answer may lie in an elegant computer model based on surprising sources.

A 62-year-old adventure mystery that has prompted conspiracy theories around Soviet military experiments, Yetis, and even extraterrestrial contact may have its best, most sensible explanation yet—one found in a series of avalanche simulations based in part on car crash experiments and animation used in the movie Frozen.

In an article published today in the journal Communications Earth and Environment, researchers present data pointing to the likelihood that a bizarrely small, delayed avalanche may have been responsible for the gruesome injuries and deaths of nine experienced hikers who never returned from a planned 200-mile adventure in Russia’s Ural Mountains in the winter of 1959.

In what has become known as the Dyatlov Pass incident, ten members of the Urals Polytechnic Institute in Yekaterinburg—nine students and one sports instructor who fought in World War II—headed into the frigid wilderness on a skiing and mountaineering expedition on January 23, 1959.

One student with joint pain turned back, but the rest, led by 23-year-old engineering student Igor Dyatlov, continued on. According to camera film and personal diaries later found on the scene by investigators, the team made camp on February 1, pitching a large tent on the snowy slopes of Kholat Saykhl, whose name can be interpreted as “Dead Mountain” in the language of the region’s Indigenous Mansi people.

The nine—seven men and two women—were never heard from again.

When a search team arrived at Kholat Saykhl a few weeks later, the expedition tent was found just barely sticking out of the snow, and it appeared cut open from the inside. The next day, the first of the bodies was found near a cedar tree. Over the next few months, as the snow thawed, search teams gradually uncovered more spine-chilling sights: All nine of the team members’ bodies were scattered around the mountain’s slope, some in a baffling state of undress; some of their skulls and chests had been smashed open; others had eyes missing, and one lacked a tongue.

Each body was a piece in a grim puzzle, but none of the pieces seemed to fit together. A criminal investigation at the time blamed their deaths on an “unknown natural force,” and the Soviet bureaucracy kept the case quiet. The lack of detail about this shocking event, an apparent massacre that transpired in a deeply secretive state, gave rise to dozens of long-lived conspiracy theories, from clandestine military tests to Yeti attacks.

In the dead of winter

In the wake of renewed media interest and pervasive outlandish hypotheses, Russian authorities recently reexamined the case around the Dyatlov Pass incident and concluded in 2019 that an avalanche was primarily responsible for the nine deaths. Key scientific details were absent from the report, however, including a clear explanation as to how an avalanche could have taken place with no documented evidence of its occurrence left behind. This led to continued doubts around the seemingly pat explanation from a government long infamous for its lack of transparency.

Many argued that the avalanche theory, initially proposed in 1959, still didn’t seem to stack up: The team’s tent encampment was cut into the snow on a slope with an incline seemingly too mild to permit an avalanche. There was no snowfall on the night of February 1 that could have increased the weight of the snow burden on the slope and triggered a collapse. Most of the blunt force trauma-like injuries and some of the soft tissue damage were atypical of those caused by avalanches, whose victims usually asphyxiate. And if an avalanche had occurred, why was there a gap of at least nine hours, according to forensic data, between the team members cutting the slope for their encampment and the eventual avalanche?

That curious delay was of particular interest to Alexander Puzrin, a geotechnical engineer at ETH Zürich, one of Switzerland’s federal institutes of technology. He had recently published a paper explaining how, strange though it may seem, an earthquake can trigger an avalanche with a gap ranging from mere minutes to several hours between the two events. While Puzrin grew up in Russia, he learned of the Dyatlov Pass story only a decade ago. He was fascinated by the infamous incident and what may have caused it, but was understandably wary of tackling the question solo.

Johan Gaume, head of the Snow Avalanche Simulation Laboratory at EPFL, another Swiss federal technical institute in Lausanne, got to know Puzrin around the time of the 2019 Russian inquiry into what happened at Dyatlov Pass. Suspecting the avalanche delay issue held one of the keys to solving the mystery, they teamed up to create analytical models and computer simulations to try and replicate the obfuscated hours that stole the mountaineers’ lives.

The scientific investigation came with an added benefit from Puzrin’s wife, who is Russian. “When I told her that I was working on the Dyatlov mystery, for the first time she looked at me with real respect,” he says.

Countering the counterarguments

The shallow slope argument against an avalanche was tackled early on: It turned out not to be all that shallow after all. The undulating topography on Kholat Saykhl, covered by snowfall, made the slope appear mild, but it was actually closer to 30 degrees, the rule-of-thumb minimum requirement for many avalanches. Reports dating back to the site’s initial investigation also describe an underlying snow layer on the mountain that didn’t clump together, providing a weak, slippery base that a lot of overlying snow could easily slide over.

“The local topography played a trick on them,” says Puzrin.

Then there was the question of the snow mass: The cut the team made in the snow to pitch their tent destabilized the slope, but additional snow had to have collected before any avalanche could happen. While weather reports record no snow that fateful night, the Dyatalov group’s diary entries note there were very strong winds. These were likely to be katabatic winds—heavy clumps of frigid air that brought large amounts of snow from higher up down toward the campsite, increasing the load on an already precarious slope and explaining the nine-hour delay between the snow cut and the avalanche.

The researchers’ computer simulations show the avalanche on Kholat Saykhl wouldn’t have been huge, perhaps involving a block of icy matter a mere 16 feet long—about the size of an SUV. The small size explains why no evidence for an avalanche was found during the initial investigation; it would have infilled the cut-out campsite before being quickly buried by fresh snowfall. But how could such a small collapse have caused such traumatic injuries?

Let it go, let it go

To answer that question, the scientists relied on some unorthodox sources of inspiration and information. Gaume explained how, a few years back, he was struck by how well the movement of snow was depicted in the 2013 Disney movie Frozen—so impressed, in fact, that he decided to ask its animators how they pulled it off. (The Walt Disney Company is majority owner of National Geographic Partners.)

Following a trip to Hollywood to meet with the specialist who worked on Frozen’s snow effects, Gaume modified the film’s snow animation code for his avalanche simulation models, albeit with a decidedly less entertaining purpose: to simulate the impacts that avalanches would have on the human body.

Code in hand, the pair then needed realistic values for the forces and pressures the human body could experience in an avalanche. This time, their information came from the automotive industry.

“We discovered that, in the 70s, General Motors (GM) took 100 cadavers and broke their ribs,” says Puzrin, “hitting them with different weights at different velocities” to see what would happen during a car crash. The data was ultimately used to calibrate the safety of seat belts.

Some of the cadavers used in the GM tests were braced with rigid supports while others weren’t, a variable which ended up being serendipitous for Puzrin and Gaume. Back on the slopes of Kholat Saykhl, the team members had placed their bedding atop their skis. This meant that the avalanche, which hit them as they slept, struck an unusually rigid target—and that the GM cadaver experiments from the 1970s could be used to calibrate their impact models with remarkable precision.

The researchers’ computer models demonstrated that a 16-foot-long block of hefty snow could, in this unique situation, handily break the ribs and skulls of people sleeping on a rigid bed. These injuries would have been severe, but not fatal—at least not immediately—says Puzrin.

Jordy Hendrikx, the director of the Snow and Avalanche Lab at Montana State University, who was not involved in the current research, has long suspected an avalanche would be the most plausible villain for the Dyatlov Pass incident, but it wasn’t obvious that Kholat Saykhl was avalanche terrain. He says the team’s simulations have now recreated the deadly night with a newfound fidelity.

“[T]he way they’ve shown that empirically in their equations seems perfectly robust,” Hendrikx says. “It’s exciting how new science developments in the avalanche world can shed new light on these historic puzzles.”

It’s a bit surprising that such a small avalanche could cause such violent injuries, says Jim McElwaine, a geohazards expert at Durham University in England who was not involved with the study. He suspects that the block of snow would have needed to be incredibly stiff and moving at some speed to accomplish this.

Freddie Wilkinson, a professional mountain climber and guide not involved with the work, says that it’s entirely reasonable that such innocuous-sounding slabs could cause acute bodily harm. “[S]ome slabs can be quite hard, and it’s very plausible they can result in blunt trauma wounds,” he says.

“I’m absolutely convinced that the tragedy was the result of wind and snow deposition, and the fact that they pitched camp in the lee of a ridge,” Wilkinson adds. “I’ve made this mistake in my mountaineering career more than once.” During an expedition to Antarctica in 2012, tents belonging to Wilkinson’s team were pitched inside a circle of wind-deflecting snow walls they made. Returning to camp after three days, his team found that two tents tucked in the wind-shielded wall were completely buried.

The avalanche that appears to have occurred on February 1, 1959, on Kholat Saykhl was an incredibly rare type of event. But rare events do occur, and this one could have come to pass only at that exact spot, at that exact moment, during that one very wintery night.

The perfect storm

What happened after the avalanche is speculation, but the current thinking is that the team cut themselves out of the smothered tent, fleeing in a panic toward temporary shelter in the treeline a mile or so downslope. Three of them were severely injured, but everyone was found outside of the tent, so it’s likely the more able-bodied survivors dragged the injured out of their smothered shelter in an attempt to rescue them. “This is a story of courage and friendship,” says Puzrin.

Most of the nine who perished on Kholat Saykhl died of hypothermia, while others may have succumbed to their injuries. The state of undress some were found in remains puzzling (paradoxical undressing may be an explanation), as do reports that note some of the bodies had traces of radioactivity (which may be a result of thorium present in camping lanterns). The missing eyes and tongue of some victims may have simply been a result of scavenging animals pecking at the dead, but that too remains an open question.

This new study doesn’t try to explain everything that happened back in 1959, and the Dyatlov Pass case will likely never be fully closed, says Gaume. This study simply offers a reasonable account of the events that ultimately triggered the deaths on Kholat Saykhl.

That matters, not least because the enigmatic tragedy remains heartbreaking for the living relatives of the victims. Some in Russia have voiced the opinion that these hikers had taken stupid or unnecessary risks that ultimately killed them. “This kind of tarnishes their legacy,” says Puzrin, whose study shows that this freak avalanche would have surprised mountaineering experts with a lifetime of experience. The Dyatlov team members, Puzrin says, were very competent people who would never have foreseen the danger of clearing a space for their tent on what looked like a gentle slope.

Gaume nevertheless fears the explanation they presented today is too straightforward for much of the public to accept. “People don’t want it to be an avalanche,” he says. “It’s too normal.” That unyielding skepticism, along with the haunting nature of the Dyatlov Pass incident, will keep conspiracy theories alive well into the future.

“To me, this story is uniquely powerful, profound, poignant, because this was a group of young people going off into the wilderness and they never came back,” says Wilkinson.

“People love to invent implausible scenarios about death in the wilderness, because we will never know 100 percent what happened.”

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