On January 27, 1959, a team of hikers from the Ural Polytechnic Institute in Russia set off on an expedition in the northern Ural Mountains, with the goal of reaching Gora Oterten Mountain. They never reached their destination, all perishing on the freezing slopes of Kholat Syakhl Mountain – translating to “Death Mountain” in the local indigenous Mansi language.

Their deaths were so disturbing and mysterious that the Dyatlov Pass Incident has become infamous, with many theories swirling around the unfortunate fates of the hikers. These range from avalanches and panic-inducing sound waves to aliens, yetis, and secret military experiments. However, a new paper published in Communications Earth & Environment suggests that a rare type of slab avalanche could have been the culprit. "The truth, of course, is that no one really knows what happened that night. But we do provide strong quantitative evidence that the avalanche theory is plausible," said co-author Professor Alexander Puzrin in a statement.

Their tent was found on February 26, 1959, cut open from within with belongings still inside. Footprints in the snow indicating they were barefoot, wearing only socks, or a single boot, led away from the tent and then disappeared.

The first two bodies were found on February 27, under a cedar tree by the remnants of a fire. The hikers had suffered burns, and one of them had bitten off his own knuckle. They were barefoot, only wearing underwear. The remains of three others were found between this site and the tent, frozen in poses implying that they were trying to return to camp. On May 4, almost three months later, the last four bodies were found in a ravine around 75 meters (246 feet) from the tree, under 4 meters (13 feet) of snow. Two had their eyes missing, one had no eyebrows, and one had had their tongue ripped out.

The question is, why did these very experienced hikers flee their tent so ill-equipped to survive? Some people blame aliens. Strange lights were seen in the sky around the time of the incident, and some of the hiker’s clothes inexplicably had traces of radiation on them. These factors have also led some to believe that the deaths were a result of a secret military or KGB operation. Others theorize that a Kármán vortex street caused panic attacks in the hikers. This is a pattern of wind that generates low-frequency waves of sound and could cause unpleasant psychological effects. Other sources – including a 2014 Discovery Channel documentary – claim a murderous yeti killed the hikers. A photo from a hiker’s camera, supposedly of a yeti but probably of someone in snow gear, has helped fuel this theory.

The avalanche theory is the least far-fetched, but there are many points that contradict it. Firstly, the rescue team didn’t find any evidence of an avalanche at the scene of the incident, and the angle of the slope above was not steep enough for a typical avalanche. The injuries to the hiker’s chests and skulls were also unusual for the victims of an avalanche.

“Previous investigators have been unable to explain how, in the absence of any snowfall that evening, an avalanche could have been triggered in the middle of the night. We had to come up with a new theory to explain it,” said co-author Professor Johan Gaume. “We use data on snow friction and local topography to prove that a small slab avalanche could occur on a gentle slope, leaving few traces behind.”

The hikers carved out a section of the slope to pitch their tent. “That was the initial trigger, but that alone wouldn't have been enough,” said Professor Puzrin. “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.”