By the time the rescue team helicoptered to the remote Dyatlov Pass in late February 1959, the nine Russian adventurers—seven men and two women, all highly experienced cross-country skiers—had been dead for nearly a month. Nothing about the scene seemed right. The adventurers’ tent had been sliced open from the inside, and in its husk lay rucksacks, neatly arranged boots, and a plate of sliced pork fat. The rescuers found the victims themselves over half a mile downslope from their camp, some of them barefoot and almost naked. The primary cause of death was hypothermia—temperatures would have been well below zero degrees Fahrenheit the night they fled—but two of the deceased were missing their eyes, and another her tongue. Four had suffered severe trauma to their heads and chests, as if they’d been in a car crash. These were not injuries consistent with a death by avalanche.
Over the decades, what became known as the Dyatlov Pass incident has prompted many a conspiracy theory. It must have been aliens that made the Russians flee to an icy death, as evidenced by the fact that some of the adventurers’ clothes bore traces of radioactivity. Or a Yeti had stumbled upon the camp. Or, more plausibly, the local humans didn’t appreciate the group’s intrusion on their lands. In the end, none of these were particularly convincing to the Russian government, which officially blamed an avalanche as the culprit, all those curious circumstances notwithstanding.
Now, more than 60 years later, scientists say they’ve got new evidence to back up that claim, but with a twist: the killer was probably a peculiar kind of avalanche. Inspired by previous work that modeled realistic snow for the Disney film Frozen, the researchers simulated how a relatively tiny avalanche could have struck the camp, forcing the adventurers to flee, and severely injuring some of them.
Sometime before nightfall on February 1, 1959, the cross-country skiers had made a simple camp, just one tent into which they’d all crammed side by side to sleep. We know this timeline because investigators recovered the group’s cameras and found an image of the pitched tent in daylight. We also know that the group evacuated quickly at night, as evidenced by the cut in the tent—perhaps done frantically, if people trapped inside couldn’t breathe—and the fact that the rescue team also recovered lanterns near the shelter.
As for the campers’ time of death, researchers have a few lines of evidence. Without body heat to keep it warm, in such cold weather—estimated to be -13°F, based on readings from the closest weather stations—a person’s watch stops ticking about an hour after their death. Three of the adventurers’ watches stopped between 8am and 9am, and another’s stopped at 5:31am. The temperature also determines the maximum survival time for an exposed human being wearing little clothing; in this case, the window should have been two to three hours. Lastly, the victims’ stomach contents showed it’d been six to eight hours since their last meals.
Putting this all together, the skiers pitched camp before nightfall, likely fled between 1:30am and 5:30am, and perished between 4:30am and 7:30am.
If you’re envisioning a typical avalanche, this doesn’t make much sense. For one thing, the rescue team didn’t see any sign of a massive movement of snow—they had easily spotted the tent, and it was not deeply buried. Plus, the slope around the tent was 23° on average, well below the 30° incline that scientists will tell you it takes to trigger an avalanche. When the adventurers had originally set up camp, they’d cut into the snow to level out a space. Yet investigators determined that the campers hadn’t fled until at least nine hours after making that cut. If the cut had triggered an avalanche, that slide should have happened immediately.
This all does make sense, though, to scientists Johan Gaume and Alexander Puzrin, who laid out their theory for the Dyatlov Pass incident today in the journal Communications Earth & Environment. (It is, incidentally, the first scientific paper I’ve ever read that mentions “attacks by Yetis.”) The conditions, they argue, could well have spawned what’s known as a delayed slab avalanche.
When the year’s first snow falls, it comes in contact with ground that’s still relatively warm. But the air temperature has fallen dramatically, creating a temperature gradient that builds a porous crystalline material, known as a weak layer, that’s 80 percent air. On top of this, more snow falls, forming a denser slab. Think of it like a parking garage, with the weak layer being the parking spaces and the sparse pillars—lots of airy space. The solid ceiling above is the slab. Now if you somehow disturb that weak layer, knocking out those pillars, it’ll collapse, releasing the slab above it as an avalanche.
Or think of what happens when you stack two books on your palm, then tilt them: the top book slides off once it reaches a critical angle. During a slab avalanche, the same thing happens with that top layer of denser snow; it slides right off the lower layer.
Critically for our scenario, a slab avalanche doesn’t require a 30° slope to trigger it—it’s more like 20°. The average slope above the adventurers’ camp was 23°, and investigators found that, at the time of the Dyatlov Pass incident, the base of the local snowpack was weak.