What happened at Dyatlov Pass, and why is it still debated?

The Dyatlov Pass incident was the death of nine experienced Russian mountaineers during a skiing expedition in the northern Ural Mountains on the night of February 1, 1959. The most widely supported modern explanation is a small slab avalanche that struck the tent. Two Russian official investigations reached that conclusion, and a 2021 physical model published in Communications Earth & Environment offered a mechanism for it. Several details remain unexplained, and other theories persist. [1]

The group camped on the slope of Kholat Saykhl, which means "Dead Mountain" in the local Mansi language. After midnight something made them cut the tent open from inside and flee toward a forest more than 1 km downslope. They were poorly dressed for temperatures below -25 °C, and strong katabatic winds were blowing after an arctic cold front passed. [1]

Search teams found the bodies between 26 days and three months later, in the forest and on the way back to the tent. Hypothermia was the main cause of death. Four hikers had severe thorax or skull injuries, two were missing eyes and one was missing a tongue. Some were almost naked and barefoot, traces of radioactivity were found on some clothing, and glowing orange spheres were reported in the sky that night. The 1959 Soviet investigation concluded that "a compelling natural force" was responsible without identifying it. [1] [2]

Many theories have been proposed, including infrasound-induced panic, animal attacks, Yetis, attacks by local tribesmen, katabatic winds, a romantic dispute, nuclear-weapons tests and a snow avalanche. The avalanche idea was once popular but was questioned for four reasons: the search team saw no obvious avalanche debris, the slope above the tent averaged under 30°, the avalanche would have come at least nine hours after the hikers cut into the slope, and the chest and skull injuries were not typical of avalanche victims. [1]

Russia's Investigative Committee reopened the case in 2015 and concluded in 2019 that an avalanche was the most probable cause. The Prosecutor General's office reached the same conclusion in July 2020. The Nature-group paper says neither investigation disclosed scientific answers to the four objections, and relatives, the public and researchers kept challenging the findings. A 2019 Swedish-Russian expedition disagreed and proposed that the direct force of katabatic winds on the tent was the main factor. [1]

Researchers Johan Gaume and Alexander Puzrin proposed that four factors combined. The tent sat beneath a shoulder in a locally steeper slope. A buried weak snow layer lay under a slab that thinned uphill. The hikers cut into the slope to pitch the tent. Katabatic winds then piled drifting snow onto the slope above. Their model puts the delay before release at 7.5 to 13.5 hours, consistent with the forensic estimate of the time of death. Simulations suggest even a small slab could cause severe but non-lethal chest and skull injuries. [1] [3]

The authors argue that the buried layer was about 28° and that critical slope angles can be as low as 20° when snow friction is low. Smoothing by later snowfall explains the milder 23° slope seen afterward. Follow-up fieldwork found slopes above 30° and filmed two recent small slab avalanches at the pass. One was visible for less than an hour, which may explain why rescuers saw no traces three weeks later. [1] [4]

The authors say their work shows only that this rare type of slab release is plausible. It does not address the radioactivity on the clothing, the hikers' behavior after leaving the tent, or the locations and condition of the bodies. They also say the 2022 conditions differed from 1959, with an eastern slope aspect, a softer slab and a steeper slope that was not undercut, and they do not treat the work as the final word. [1] [4]