Mechanisms of slab avalanche release and impact in the Dyatlov Pass incident in 1959

We show how a combination of irregular topography, a cut made in the slope to install the tent and the subsequent deposition of snow induced by strong katabatic winds contributed after a suitable time to the slab release, which caused severe non-fatal injuries, in agreement with the autopsy results

During the night of February 1, 1959, nine Russian hikers died under unexplained circumstances during a skiing expedition in the northern Ural Mountains.

The group had decided to set up their camp on the slope of the Kholat Saykhl (Fig. 1a); the name means “Dead Mountain” in the local Mansi language.

Something unexpected happened after midnight that caused expedition members to cut the tent suddenly from the inside and escape towards a forest, more than 1 km downslope (Fig. 1b), without appropriate clothes, under extremely low temperatures, and in the presence of strong katabatic winds induced by the passing of an arctic cold front.

A Last picture of the Dyatlov group taken before sunset, while making a cut in the slope to install the tent.

C Configuration of the Dyatlov tent installed on a flat surface after making a cut in the slope below a small shoulder.

Snow deposition above the tent is due to wind transport of snow

Methods

Problem formulation for the analytical model of delayed avalanche release.

We assume a plane strain problem with a cut in a curved slope, with a planar slope-parallel weak layer of angle α, thickness d at the depth h described by a parabolic equation: where h0 is the depth of the weak layer at the cut (x = 0), hc is the constant depth of the weak layer at the upper straight portion of the slope \(\left( {x \ge l_{\mathrm{c}}} \right)\), lc is the distance from the cut to the point on the slope where the slope surface becomes parallel to the weak layer.

The choice of the parabolic slope approximation has been based on the following considerations.

It reflects a smooth uphill steepening of the slope.

It leads to a second-order Euler–Cauchy differential equation with a simple analytical solution.

Results

Around 100 m above the tent, there is a shoulder which separates a rather flat plateau and a steeper slope below (Fig. 2a).

This slope consists of 4–6 m high steps (Fig. 1c and Fig. SF2) and the tent was installed below one of them, where it was easier to make a cut in a locally flatter slope.

The choice of the tent location was likely driven by the fact that the larger scale shoulder would protect them from the strong winds.

As we show below, this choice of location could have contributed to the accident: small scale topographic variability resulted in a locally steep weak snow layer while the larger shoulder contributed to significant wind-driven snow accumulation above the tent, eventually leading to an instability

Conclusion

Significant progress in snow and avalanche research over the past two decades has allowed better understanding of avalanche dynamics and of the processes related to snow-slab avalanche release.

These developments include a snow slab with a spatially variable thickness and its evolution due to sintering of the wind-transported snow, which affects the instability of a buried weak snow layer.

Our numerical simulation of the impact of a snow avalanche on a human body constrained by an obstacle combines advanced elastoplastic constitutive models with large-deformation dynamic numerical analysis (MPM) and biomechanical modeling of the human body.

This opens new perspectives for research on the effects of snow avalanches on human health and safety

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