'Death of the Dyatlov Hiking Group') was an event in which nine Soviet ski hikers died in the northern Ural Mountains between February 1 and 2, 1959, under uncertain circumstances.

The experienced trekking group from the Ural Polytechnical Institute, led by Igor Dyatlov [ru], had established a camp on the eastern slopes of Kholat Syakhl in the Russian SFSR of the Soviet Union.

Numerous theories have been put forward to account for the unexplained deaths, including animal attacks, hypothermia, an avalanche, katabatic winds, infrasound-induced panic, military involvement, or some combination of these factors.

The group arrived by train at Ivdel (Ивдель), a town at the centre of the northern province of Sverdlovsk Oblast in the early morning hours of January 25, 1959.

On January 28, one member, Yuri Yudin, who had several health ailments (including rheumatism and a congenital heart defect), turned back due to knee and joint pain that made him unable to continue the hike.

It seems they planned to get over the pass and make camp for the next night on the opposite side, but because of worsening weather conditions—snowstorms and decreasing visibility—they lost their direction and deviated west, toward the top of Kholat Syakhl.

When they realised their mistake, the group decided to set up camp there on the slope of the mountain, rather than move 1.5 kilometres (0.93 mi) downhill to a forested area that would have offered some shelter from the weather.

Nine sets of footprints, left by people wearing only socks or a single shoe or even barefoot, could be followed, leading down to the edge of a nearby wood, on the opposite side of the pass, 1.5 kilometres (0.93 mi) to the north-east.

Between the pine and the camp, the searchers found three more corpses: Dyatlov, Kolmogorova, and Slobodin, who died in poses suggesting that they were attempting to return to the tent.

[citation needed] There was initial speculation that the indigenous Mansi people, reindeer herders local to the area, had attacked and murdered the group for encroaching upon their lands.

Several Mansi were interrogated,[25] but the investigation indicated that the nature of the deaths did not support this hypothesis: only the hikers' footprints were visible, and they showed no sign of hand-to-hand struggle.

[citation needed] Journalists reporting on the available parts of the inquest files claim that it states: At the time, the official conclusion was that the group members had died because of a compelling natural force.

[35] A large part of the book includes broad quotations from the official case, diaries of victims, interviews with searchers and other documentaries collected by the film-makers.

The narrative line of the book details the everyday life and thoughts of a modern woman (an alter ego of the author herself) who attempts to resolve the case.

[37] On 1 July 2016, a memorial plaque was inaugurated in Solikamsk in Ural's Perm Region, dedicated to Yuri Yudin (the sole survivor of the expedition group), who died in 2013.

[38] On 11 July 2020, Andrey Kuryakov, deputy head of the Urals Federal District directorate of the Prosecutor-General's Office, announced an avalanche to be the "official cause of death" for the Dyatlov group in 1959.

Kuryakov noted that although the skiers made an error in the placement of their tent, everything they did subsequently was textbook: they conducted an emergency evacuation to ground that would be safe from an avalanche, they took shelter in the woods, they started a fire, they dug a snow cave.

At some point, some of the clothes may have been recovered or swapped from the dead, but at any rate, the group of four whose bodies was most severely damaged were caught in an avalanche and buried under 4 meters (13 ft) of snow (more than enough to account for the 'compelling natural force' the medical examiner described).

First of all, the ICRF investigators (one of them an experienced alpinist) confirmed that the weather on the night of the tragedy was very harsh, with wind speeds up to hurricane force, 20–30 metres per second (45–67 mph; 72–108 km/h), a snowstorm and temperatures reaching −40 °C (−40 °F).

These factors were not considered by the 1959 investigators who arrived at the scene of the accident three weeks later when the weather had much improved and any remains of the snow slide had settled and been covered with fresh snowfall.

[51] Another hypothesis popularised by Donnie Eichar's 2013 book Dead Mountain is that wind going around Kholat Syakal created a Kármán vortex street, which can produce infrasound capable of inducing panic attacks in humans.

[53][54] According to Eichar's theory, the infrasound generated by the wind as it passed over the top of the Holatchahl mountain was responsible for causing physical discomfort and mental distress in the hikers.

This theory alleges that the hikers, woken by loud explosions, fled the tent in a shoeless panic and found themselves unable to return for supply retrieval.

[55] Parachute mines detonate while still in the air rather than upon striking the Earth's surface and produce signature injuries similar to those experienced by the hikers: heavy internal damage with relatively little external trauma.

The theory coincides with reported sightings of glowing, orange orbs floating or falling in the sky within the general vicinity of the hikers and allegedly photographed by them,[56] potentially military aircraft or descending parachute mines.

[57] Some speculate that the bodies were unnaturally manipulated, on the basis of characteristic livor mortis markings discovered during an autopsy, as well as burns to hair and skin.

[58] A similar theory alleges the testing of radiological weapons and is based partly on the discovery of radioactivity on some of the clothing as well as the descriptions of the bodies by relatives as having orange skin and grey hair.

However, radioactive dispersal would have affected all, not just some, of the hikers and equipment, and the skin and hair discoloration can be explained by a natural process of mummification after three months of exposure to the cold and wind.

The initial suppression by Soviet authorities of files describing the group's disappearance is sometimes mentioned as evidence of a cover-up, but the concealment of information about domestic incidents was standard procedure in the USSR and thus far from peculiar.

[59] International Science Times posited that the hikers' deaths were caused by hypothermia, which can induce a behavior known as paradoxical undressing in which hypothermic subjects remove their clothes in response to perceived feelings of burning warmth.