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 the “trauma 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 was “overwhelming 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 were “post-mortem changes” due to natural

decomposition after months of exposure to running water.

But two theories in particular, each involving an “overwhelming 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 the “big 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 powerful “falling wind” that 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.