Post-release careers: Tracking expeditions reveal avalanches at Dyatlov Pass

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However, the question of the irregular topography remained open. Fortunately, Radiotelevisione Svizzera (RSI) decided to produce a documentary “The Dyatlov Mystery” centered on our work. We helped them organize two expeditions to the Dyatlov Pass, one during the winter in March 2021, the other in late summer in September 2021. Due to the snowfall, the winter expedition will not couldn’t help us much with the topography of the land, but proved invaluable. later. The summer expedition, however, was equipped with a drone that allowed us to produce a high-resolution three-dimensional digital model of the terrain near the possible tent locations (Fig. 2). Obviously the steps have inclines greater than 28 degrees and many inclines are even greater than 30 degrees. Moreover, these slopes are not only local, they are continuous: no matter where you pitch your tent, you are likely to be below one of them.

Fig. 2: Local topography.

a Digital Elevation Model (DEM) showing the local slope angle. The DEM was obtained based on drone photogrammetry analysis (summer 2021 survey) and has a resolution of 9 cm. b Section A–A′ showing that although the average angle of slope is about 20°, the locally steeper steps do have an inclination greater than 30° (given as an indication by the white dotted line).

Finally, we had to investigate the objection that this area is not susceptible to avalanche hazard. In the Handbook of Natural Hazards of the Russian Federation5 from 1997, the Dyatlov Pass area is characterized as the category II avalanche danger zone, defined as at least one avalanche per kilometer every 10 years. January is reported as the most dangerous month. However, the resolution of the hazard map was extremely low, allowing critics to assert that the Category II risk refers to the western slopes of the mountain range and not the eastern slopes, where the tent of the Dyatlov group was found. .

And here the story takes an almost mysterious turn. In October 2021, we were contacted by a roller coaster guide, Dmitriy Borisov, who had photographed a feature on March 29, 2021 on the western slope of a nearby mountain (Fig. 3a,b), about 3 km from the tent place. It looked like a local depression in the slope with probable avalanche traces. But we feared it was also the shadow of a cloud. Then RSI director Matteo Born went through the footage he took for the documentary on his own winter expedition and accidentally discovered the same features only in higher resolution (Fig. 3c and Supplemental Movie 1) – taken the next day, March 30! It is very unlikely that a cloud will stay in one place for nearly 24 hours. Although it is difficult to confirm the type of snow slope instability based on the resolution of this image, the dark area below the ridge could be a pull crown failure resulting from one or more slab avalanches. . A dozen international avalanche scientists or practitioners we spoke to suggested that these could be classified as either a snow ledge, ledge falls or small wind slab avalanches.

Fig. 3: Avalanches near Dyatlov Pass.
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a Location of the area where avalanches have been observed. Source: Google Earth © 2021 Maxar technologies Landsat/Copernicus. b Photo taken by Dmitriy Borisov on March 29, 2021 from Dyatlov Pass. The area highlighted in red is located approximately 3 km from the tent. vs Image taken from a video taken by Matteo Born (director of the film RSI), the next day, March 30, 2021. D Photo of a crown traction fracture on the left side of this slope taken by Dmitriy Borisov on January 29, 2022. and Photo of a small slab avalanche in the middle of the slope by Dmitriy Borisov on the same day (January 29, 2022).

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