However, the resolution of the hazard map was extremely low, allowing the critics to claim that the Category II risk refers to western slopes of the mountain chain and not to the eastern ones, where the Dyatlov groupвЂ™s tent was found.ДЄnd here the story takes an almost mysterious turn.

January is flagged as the most dangerous month. In the Russian Federation Natural Hazards Handbook 5 of 1997, the area of Dyatlov Pass is characterized as the avalanche risk zone of Category II, defined as at least one avalanche per kilometer every 10 years. Astonishingly, her best estimate of the wind velocity above the tent was 9 to 12вЂ‰m/s, right in the range required to explain the observed delay in the slab avalanche release in our model.ДЇinally, we had to investigate the objection that this area is not susceptible to avalanche hazard. Moreover, the snow transfer by wind during winter in this area can reach 600вЂ“1000вЂ‰m 3/m, which would completely cover local topographic features such as the steps. The second scientist, Professor Galina PigolвЂ™tsina at the Voeikov Main Geophysical Observatory in St Petersburg, reports 4 that during the night of the incident, 1stвЂ“2nd of February 1959, the snow cover above the tent exceeded 150вЂ‰cm, consistent with our assumptions. Professor Victor Popovnin at the Moscow State University, a leading snow avalanche researcher in Russia, confirmed that the assumptions on the snow properties that we used in our models are consistent with his measurements during a winter expedition to Dyatlov Pass in 2019. This was worrying.ДЇortunately, we found the names of two prominent Russian scientists, who had helped the local prosecutor after the Dyatlov Group criminal case was reopened in 2019. The main objections to our conclusion of a snow avalanche were: (i) there was no snow cover on the slope, (ii) there was no wind that night, (iii) there is no significant snow transfer by wind in that area, (iv) the slope is flat (no steps), and (v) snow avalanches never happen in this area. Such a high angle makes a slab avalanche possible, because a buried weak snow layer would follow this steep terrain. Equally significantly, the topography of the slope is irregular, built of 4-to-6вЂ‰m-high steps: although the average slope inclination (observed when the steps are covered by snow) is indeed too low for an avalanche to release, we assumed (based on the evidence available at that time), that a locally steeper slope above the tent had an inclination of at least 28 degrees. One important ingredient of our proposed mechanism is the progressive wind-blown snow accumulation on the slope above the hikersвЂ™ tent. Using basic physics, we showed that in spite of a lower-than-usual apparent slope angle, scarcity of avalanche signs, uncertainties about the trigger, and unusual injuries of the victims, such an avalanche is indeed a possible explanation.

In our study 1, we focused on the plausibility of a snow slab avalanche as the trigger. The deaths of the mountaineers had variously been 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.

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