In February 1959, nine experienced Russian hikers perished in the northern Ural Mountains under unexplained circumstances. The Dyatlov Pass incident has captivated researchers and the public for decades due to the unusual circumstances surrounding the deaths and the conflicting evidence. Initial investigations proposed various theories, including animal attacks, military intervention, and even the paranormal. However, the most prevalent theory, a snow avalanche, faced significant challenges. The slope angle was lower than typical for avalanches, there was a scarcity of avalanche debris, the trigger mechanism remained unclear, and the victims' injuries were atypical of avalanche fatalities. This study tackles these contradictions and seeks to provide a physically sound mechanism explaining the event. The importance of this study stems from its potential to improve our understanding of snowpack instability and avalanche dynamics, particularly in the context of complex topography and wind-induced snow accumulation. It addresses a long-standing enigma while providing valuable insights into a previously unexplored aspect of avalanche triggers, namely the delayed onset and unique impact forces arising from a combination of factors.

The literature review examines prior investigations into the Dyatlov Pass incident and the existing theories to explain it. These include discussions surrounding the inadequacy of the initial avalanche hypothesis due to the insufficient slope angle (below 30°), the lack of typical avalanche signs, and the unusual nature of the victims' injuries. The existing literature reveals several investigations conducted over the years, often reaching conflicting conclusions, with some rejecting the avalanche theory altogether. Previous attempts to explain the incident lacked a comprehensive quantitative physical model that could reconcile the evidence with the avalanche hypothesis. The review highlights the need for a mechanism that incorporates the irregular topography of the site, the effects of strong katabatic winds, and the potential influence of the hikers' actions in modifying the snowpack.

This study uses a combination of analytical modeling and numerical simulations to investigate a delayed avalanche release mechanism. The analytical model considers the following factors: (1) The irregular topography of the slope, featuring a shoulder above the tent creating an area of preferential snow accumulation; (2) A buried weak snow layer, potentially a depth hoar layer, parallel to the terrain; (3) A cut in the snowpack made by the hikers to install their tent, weakening the snowpack; (4) Strong katabatic winds leading to progressive wind-blown snow accumulation above the tent. The model incorporates the spatial variability of snow slab thickness and its evolution due to the wind-transported snow. Equations are derived to describe the shear stress in the weak layer, and the conditions for delayed avalanche release are analyzed. Numerical simulations, employing the Material Point Method (MPM), are used to model the slab avalanche dynamics and the impact on the human body. The MPM model simulates the complex interactions between the snow slab, the tent, and the human body, considering material properties, large deformations, and fracture propagation. The model accounts for the impact velocity, volume, and density of snow blocks, and allows for determining the resulting injuries based on biomechanical models and the Abbreviated Injury Scale (AIS). This methodology allows the researchers to quantitatively assess the plausibility of their proposed mechanism and compare the simulation results to the observed injuries of the Dyatlov group.

The study's key findings include: (1) A novel mechanism for delayed avalanche release is proposed, considering the combination of irregular topography, a weak snow layer, a cut in the slope, and strong katabatic winds. (2) The analytical model shows that even with a relatively mild average slope angle, a slab avalanche could have been triggered after a delay of 7.5 to 13.5 hours, consistent with the forensic estimations. (3) Numerical simulations demonstrate that a relatively small slab avalanche could have caused the severe, non-fatal injuries reported in the autopsy results. This is due to the specific conditions of the impact, where the victims were constrained between the falling slab and the tent floor. (4) The model predicts a snow deposition flux consistent with the wind velocities observed in nearby weather stations on the night of the accident. (5) The simulated avalanche impact velocity is around 2 m/s, capable of producing the observed injuries based on biomechanical modeling. (6) The study confirms that even a slope angle slightly below the often-cited 30° threshold can initiate an avalanche when other factors, including low dynamic friction and wind-driven loading, are taken into account. This is consistent with the lower slope angle observed at the incident site. (7) The model also suggests that the construction of a snow parapet, a common safety measure in snow camping, could have accelerated the avalanche.

The findings of this study strongly support the hypothesis that a slab avalanche was indeed the cause of the Dyatlov Pass incident. The proposed mechanism resolves previous inconsistencies by providing a quantitative explanation for the delayed avalanche release, the observed injuries, and the lack of extensive avalanche debris. This mechanism highlights the critical role of specific local conditions, including irregular topography, weak layers, and strong winds, in triggering avalanches. The results suggest that the often-used minimum slope angle of 30° for avalanche initiation may be an oversimplification and that other factors such as wind-loading and low dynamic friction can significantly reduce the critical slope angle. The study’s findings have significant implications for improving avalanche risk assessment and forecasting, particularly in complex terrains subject to strong winds. The work emphasizes the necessity of considering the cumulative effects of various factors rather than relying solely on simplified criteria for avalanche initiation.

This study presents a novel mechanism that successfully explains the Dyatlov Pass incident. By combining analytical modeling and numerical simulations, the researchers demonstrate how a combination of factors, including irregular topography, weak snow layer, a cut in the slope, and wind-driven snow accumulation, led to a delayed slab avalanche causing the observed injuries. This work enhances our understanding of avalanche dynamics and highlights the need for more comprehensive risk assessments that account for complex interactions between terrain, snowpack properties, and weather conditions. Future research could focus on validating this mechanism through additional field studies and expanding the model to encompass a wider range of scenarios and snowpack conditions.

The study relies on certain assumptions and estimations due to the limited data available regarding the precise snowpack properties and wind conditions on the night of the incident. While the model incorporates a range of plausible values for relevant parameters, uncertainties remain, particularly concerning the exact characteristics of the weak layer and the precise wind speed and direction. Furthermore, the model simplifies some aspects of the avalanche dynamics, such as the interaction between the falling snow slab and the tent, and the precise distribution of the impact forces on the victims. Nevertheless, the model provides a robust framework for understanding the event.