On April 25, 2015, rescuers use a makeshift stretcher to carry an injured person after an avalanche triggered by an earthquake flattened parts of Everest Base Camp. Victims were airlifted out. Image credit: Roberto Schmidt/AFP/Getty Images

On April 18, 2014, an avalanche killed 16 Nepalese guides on Mount Everest, making it the deadliest day in the mountain’s history. One year later, a 7.8-magnitude earthquake triggered another fatal avalanche that killed more than 20 climbers and shut the mountain down for the season. Unfortunately, this year is following the trend. During this year's climbing season, six people died while attempting to summit Everest.

At 29,029 feet, Everest is known for its dangers; that's part of the allure. But in recent years, tragedies have spiked, and frozen bodies scattered across the mountain are an eerie reminder of the growing hazards. 

So why is the world’s tallest mountain claiming more lives than ever before?


Everest tragedies are nothing new; since 1990, at least one climber has died in pursuit of the summit every year. But each climbing season, Everest is getting more unstable. According to Kent Clement, a professor of outdoor studies at Colorado Mountain College, climate change is possibly the most imminent risk for climbers.

“Recently, we haven’t seen many health-related deaths—the majority of Everest fatalities are linked to avalanches and earthquakes,” Clement said. “As temperatures rise, Everest’s thousands of feet of ice and water are becoming unstable, making the mountain even more volatile.”

Collapsing seracs—50- to 100-foot columns of ice formed by intersecting glacier crevasses—are a growing threat.

Seracs can stand perfectly still for decades, then spontaneously fall over, killing those nearby and, in some cases, triggering avalanches further down the mountain. Case in point: The deadly 2014 avalanche that killed 16 sherpas was caused by a serac collapse.

As you’d expect, climate-related risks are the new norm. A study in The Cryosphere [PDF] journal predicts that Mount Everest’s glaciers could shrink by 70 percent this century.


While climate change and corresponding natural disasters may be the leading cause of casualties, Everest climbers still face a number of dangerous health risks.

In high-altitude settings, oxygen doesn’t diffuse into a climber’s blood as well as it would at sea level, which can lead to serious medical problems, including pulmonary edema, in which fluid from the blood vessels going into the lung tissue leaks into air spaces, causing a climber to drown in their own fluids; and high-altitude cerebral edema (HACE), in which fluid from blood vessels in the brain leaks out, causing intracranial pressure, headaches, neurologic dysfunction, brainstem herniation, coma, and eventually death if not treated (and in some cases, even when treated).

In terms of Everest health risks, both of these issues are particularly dangerous because they can happen to anyone during high-altitude ascents—even the most experienced climbers.

“Altitude illness impacts people in different ways, and we don’t really know who is susceptible until they have altitude illness,” Christopher Van Tilburg, the medical director of occupational and travel medicine at Oregon's Providence Hood River Memorial Hospital, told mental_floss. One of Van Tilburg's specialities is mountain emergency medicine. “High-altitude pulmonary edemas can hit people suddenly—even highly trained, fit mountaineers.” 


Another health risk that affects a climber’s cognition is hypoxia, which is simply when the brain doesn’t get enough oxygen. According to Clement, hypoxia can drastically impair judgment, making it one of the most dangerous Everest risks of all.

“The higher you climb, the more your judgment gets impaired,” Clement said. “It’s amazing how hard it is for smart people to do simple math and memory problems at high altitudes.”

In addition to treacherous missteps, hypoxia can drive climbers to push harder and go further than they normally would—but not in a good way. These “cognitive traps” often happen when a person invests significant time or money into something, such as climbing Everest. As a climber gets closer to the top, they replace logic and safety with stubborn determination, and will put everything at risk to reach the summit.

According to Clement, the cure for cognitive traps is setting a strict turnaround time: an ironclad moment when a climber promises to turn around and forego the summit to save their life. Turnaround times are decided before setting foot on Everest, and should be agreed upon between climbers and their guides.

Unfortunately, these guide-and-climber turnaround promises aren’t always upheld.

“Every time you ignore your turnaround time, you’re putting yourself at risk,” Clement said. “Professional guides are also supposed to follow these rules, but they get stuck in cognitive traps, too, because the more clients they get to the top, the more clients they’ll have next season.”


Any climb above 19,000 feet—the altitude known as “the death zone”—will have associated health risks, but the climbing industry has made significant strides with medicine and safety gear. Medicines include Diamox, a diuretic that helps prevent a mild edema, and Decadron, a steroid used to treat a brain edema and reverse the symptoms of acute mountain sickness (but the only true fix for acute mountain sickness is descent).

While the climbing industry is constantly innovating, experienced mountaineers know that new medicines and inventions will never be a match for treacherous Mount Everest.

“Training doesn’t really offset objective hazards like rock falls, ice falls, avalanches, and earthquakes,” said Van Tilburg. “And while we have medicine for altitude illness to help people acclimatize, we don’t have medicines for the myriad other risks on Everest.”