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  • This is the last photo taken by a group of experienced Russian hikers, the night they

  • disappeared in February 1959.

  • Here, in the remote Ural Mountains in Western Siberia.

  • They were on an advanced winter hiking trip, trekking hundreds of kilometers through frozen

  • wilderness.

  • The photo shows them digging a platform in deep snow, to pitch their tent along the slope

  • of Kholat Syakhl,

  • which translates from the language of the indigeous people of the region, the Mansi,

  • to Dead Mountain.

  • Hours later, the hikers abandoned the tent and all of their equipment in the dark.

  • Weeks later, a search party found the tent, half-destroyed, and covered in snow.

  • It had been cut open from the inside.

  • Frozen bodies, most of them barefoot and wearing just their sleeping clothes, were found 1,500

  • meters away.

  • Meaning something drove the group from the tent so fast, there wasn't even time to

  • unbutton its entrance

  • or put on the heavy winter gear necessary to survive the conditions outside.

  • It would take another 2 months to locate the rest of the group.

  • All of them dead, their autopsies revealing severe injuries that were hard to explain.

  • Dozens of theories, from alien encounters to government cover-ups, have developed ever

  • since.

  • But basically every theory tries to answer the same question:

  • What made them leave their tent in the first place?

  • The deeper you go into the Dyatlov Pass incident, named after the group's leader, 23 year

  • old Igor Dyatlov, the less things tend to add up.

  • So, for the sake of this video, and explaining what potentially happened that night,

  • let's stick to the most basic facts.

  • This is a rough diagram showing where the bodies of the 9 hikers were found in relation

  • to the abandoned tent,

  • stitched together from hand-drawn maps made during the initial investigation and from

  • descriptions in the case files.

  • The bodies were found in three groups.

  • These six died of hypothermia, the rest from traumatic internal injuries.

  • These two visuals will help piece together a picture of what happened to the group after

  • they left the tent.

  • The search party found footprints leading away from the tent that disappeared into the

  • snow after about 500m.

  • Continuing in their direction led to the discovery of the first two bodies.

  • Under a cedar tree 1,500m downslope from the tent.

  • They were wearing almost nothing, and had built a small fire.

  • They froze to death.

  • Three more were found after that in a straight line from the tree, as if they were trying

  • to make it back to the tent.

  • Which in -30 degree temperatures and without proper clothes, was basically impossible.

  • They also froze to death.

  • The last four weren't found until about 2 months later.

  • Buried under four meters of snow in a ravine.

  • And this is where the investigation starts to get more confusing.

  • Because, unlike the rest of the group, three of them had experienced severe internal trauma.

  • Dubinina and Zolotaryov had multiple broken ribs, and Thibeaux-Brignolle had a major skull

  • fracture.

  • Internal injuries that their autopsy reports determined were fatal.

  • The investigation's forensic expert compared their injuries to thetrauma that results

  • from the shock wave of a bomb.”

  • But there was more.

  • Zolotaryov and Dubinina were missing their eyes, and Dubinina was missing her tongue.

  • She, along with Kolevatov, were wearing clothes that were contaminated with excessive amounts

  • of radioactive substances.

  • In spite of many unanswered questions, the lead Soviet investigator, Lev Ivanov, closed

  • the case on May 28, 1959.

  • He concluded that no crime was committed, citing the hikers' lack of external injuries,

  • and that all their valuables were intact.

  • And that the cause of death wasoverwhelming force, which the hikers were not able to overcome.”

  • Since then, dozens of theories have attempted to explain what happened that night in 1959:

  • Murder at the hands of the KGB.

  • A Yeti attack.

  • Soviet military experiments gone wrong.

  • And, of course, UFOs.

  • Most of these theories lack substantial evidence.

  • And some of the more disturbing elements of the case are aren't so mysterious after

  • all.

  • The missing soft tissue, Zolotaryov and Dubinina's eyes and Dubinina's tongue, for instance.

  • Their bodies were found in a creek, and Dubinina in particular was found face down.

  • The coroner concluded at the time that these werepost-mortem changesdue to natural

  • decomposition after months of exposure to running water.

  • But two theories in particular, each involving anoverwhelming force,” offer plausible

  • solutions to the two most important questions of the case.

  • What drove the hikers to abandon the tent the way they did,

  • and what could have caused the tremendous internal injuries that some of them sustained.

  • One of these theories has been considered, and debunked, for years.

  • Avalanche.

  • Because this area isn't considered prone to avalanches, and the internal injuries don't

  • match those typically found in avalanche victims,

  • who mostly die from asphyxiation after being swept away by snow,

  • this theory has often been disregarded.

  • But a scientific paper published in January 2021 demonstrates that the hikers could have

  • been hit by a very specific kind of avalanche.

  • GAUME: My name is Johan Gaume, and I'm a professor at the Swiss Federal Institute of Technology

  • and I study snow avalanches.

  • Johan Gaume, and his colleague, geotechnical engineer Alexander Puzrin,

  • developed a model that simulates a rare type of avalanche that could have impacted the

  • tent.

  • A delayed slab avalanche.

  • ARCHIVE: The entire slab moves almost instantaneously.

  • As it races down the slope it breaks into large blocks.

  • At its actual speed, it becomes evident why the wind slab is called thebig killer.”

  • A slab avalanche occurs when a heavy concentration of snow forms on a less concentrated weak

  • layer.

  • GAUME: And when the weak layer fails, this failure will propagate across the slope and

  • eventually release a slab avalanche.

  • In the Dyatlov case, the trigger for a slab avalanche would have been cutting the slope

  • in order to pitch the tent.

  • But whatever drove them down the mountain occurred hours after that.

  • GAUME: We believe that the strong winds brought some additional snow on top of the tent.

  • And this led to progressive accumulation and ultimately the failure of the weak layer,

  • and the avalanche which impacted the tent and hikers.

  • And we showed that this type of impact could explain the injuries of some of the hikers.

  • Trapped under the slab, and potentially fearing a second avalanche,

  • they cut their way out of the tent and made for the tree line for protection.

  • This theory, constructed by data-driven simulations and models, shows that a delayed slab avalanche

  • was possible in these conditions,

  • and could account for the traumatic injuries within the group.

  • And doesn't attempt to explain anything beyond what drove them from the tent,

  • like why the group was so underdressed.

  • GAUME: We say that this is possible, that such a slab avalanche would have injured them

  • the way they were injured.

  • Everything after the avalanche is out of the scope of our paper.

  • HOLMGREN: It's not difficult to die on Kholat Syakhl, on the Dead Mountain.

  • Richard Holmgren is a Swedish archaeologist who led an expedition that retraced the steps

  • of the Dyatlov group in 2019.

  • His group has a different explanation for how these injuries occurred.

  • HOLMGREN: The goal was to go there exactly at the same time.

  • And we wanted to put the tent there exactly the same night.

  • We thought that this might help us to understand their situation.

  • And after experiencing the severe weather of the region, his group came to one main

  • conclusion.

  • HOLMGREN: In my view, the katabatic scenario is the only theory that would explain all

  • the steps.

  • A katabatic wind is a powerfulfalling windthat travels down a mountain slope,

  • quickly gaining speed under the force of gravity, and can create hurricane-like conditions without

  • warning.

  • HOLMGREN: In a katabatic scenario, it goes very fast from strong winds to uncontrollable

  • strong winds.

  • It can change dramatically in seconds, it doesn't take any time.

  • If this scenario hit the Dyatlov hikers, the canvas tent would be at risk of being torn

  • apart, and would need to be evacuated immediately.

  • HOLMGREN: It's a matter of seconds, so the natural procedure to do in this case would

  • be to cut yourself out very quickly.

  • And with temperatures around -30 degrees celsius, their equipment would have been frozen stiff.

  • HOLMGREN: I know myself, just putting on one boot in these circumstances takes three to

  • four minutes. One boot.

  • In the katabatic wind scenario, no one in the Dyatlov group is seriously injured at

  • the tent.

  • And these hypothermia deaths are explained the same way.

  • The injuries happen in the ravine where the bodies were found.

  • Remember, these bodies were found buried under around four meters of snow.

  • They may have dug themselves a snow den for shelter that collapsed and crushed them.

  • HOLMGREN: The compressed chests were caused when the heavy snow collapsed over them.

  • And it got heavier during the spring, during thawing.

  • The injuries could even be post-mortem.

  • By the time the bodies were found, they had been decomposing under a crushing snowpack

  • for months.

  • On a freezing cold night in February, 1959, 9 experienced hikers dug a platform into a

  • slope to pitch their tent.

  • Hours later, something happened suddenly that drove them into unsurvivable cold without

  • proper clothes.

  • A slab avalanche or katabatic wind are just two of many theories.

  • And they actually have a lot of crossover.

  • The slab avalanche theory needs katabatic wind to explain the snow transfer from the

  • top of the slope.

  • And the collapsed snow den in the katabatic theory is explained by a soft snow layer,

  • the shelter they dug, buckling under a heavy slab.

  • Both give compelling reasons for the Dyatlov group to abandon their tent, and offer a plausible

  • explanation for the mysterious injuries.

  • Ultimately though, since there were no survivors, trying to account for why the hikers did the

  • things they did ends up raising more questions than answers.

  • GAUME: This is one of the most mysterious parts of the Dyatlov Pass incident

  • The behavior of the hikers after the incident, after what happened during this night, is

  • probably the thing that will never be explained.

This is the last photo taken by a group of experienced Russian hikers, the night they

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