Everest has always been a dangerous place, and 2016 has just seen its first deaths of the climbing season. Since last Thursday, Everest has claimed four lives, and two people remain missing.
A 25-year-old named Phurbu Sherpa fell while trying to fix a route just 150 meters below Everest’s summit on Thursday. Eric Arnold of the Netherlands died on Friday while coming back from the summit–a heart attack is suspected. Maria Strydom of Australia died somewhere between Camp IV and the summit on Saturday after a rescue attempt to reach her failed. And Subash Paul died of altitude illness at Base Camp II on Sunday. Two of his teammates have been missing since Saturday are still unaccounted for, according to CNN.
Whenever these first deaths of the season happen–and they inevitably do–it’s easy to say that Everest just isn’t what it used to be. Many of those who perish are a part of the guiding industry–either clients, Western guides or Sherpas–that have overtaken the mountain in recent decades. Some might say that Everest was once was the zenith of exploration, and today it’s a circus of guided groups, frozen bodies and undecomposed human waste. And while it’s true that the experience of climbing Everest has changed dramatically, many of the challenges involved in an ascent remain the same. Here’s the science behind why Everest is such a dangerous and deadly place:
Acute mountain sickness (AMS)
Acute mountain sickness (AMS) is a whole host of symptoms that can occur due to reduced air pressure and oxygen levels at high altitude. Minor symptoms include dizziness, headaches, loss of appetite, and nausea (climbers often describe it as feeling like a hangover). While many–if not the majority–of Everest climbers will experience AMS, the real danger is when it progress into one of its more serious forms:. “That lack of oxygen causes a number of problems in every organ system in the body,” says Dr. Alan Oram, an emergency physician and medical advisor to the American Mountain Guides Association. “It can cause pulmonary edema and cerebral edema, which are both life-threatening complications from the lack of air.”
Some form of AMS directly caused 8% of deaths from 1950 to 2009 on peaks above 6,000 meters, including Everest, according to research by Elizabeth Hawley and Richard Salisbury at the Himalayan database.
Falls
Falls can happen from a myriad of causes, but most often from human error. It’s possible there’s some conflation between fall deaths and AMS deaths, too. “Any time you have a lack of oxygen, your ability to make decisions and for your brain to function normally is impaired,” Oram says.
32% of extreme high-altitude deaths come from falls. “AMS may be a hidden factor that was not known or accurately reported; for example, AMS may well have caused a few falls during descents from summit bids of the 8000m peaks, even though it went unreported,” Hawley and Salisbury write in their report Himalaya by the Numbers.
Avalanches
Avalanches happen due to instability in the snow pack, which is caused by variations in precipitation, wind and temperature over time. The most common type of avalanche is a slab avalanche, where a large, consolidated layer of snow separates from a hard sliding surface (like a layer of ice) and falls down the slope. Some avalanches happen on their own, and others are triggered by humans when they travel across a weak point in the snowpack.
35% of deaths on Himalayan peaks above 6,000 meters are caused by avalanches. Interestingly, avalanches account for 46% of deaths for hired personnel (Sherpas and guides), likely because they spend more time setting up equipment in avalanche terrain and are less likely to fall prey to altitude illness or falls. Avalanches cause 29% of deaths for regular expedition members, be they independent climbers or clients in a guided expedition.
Exposure, Frostbite And Exhaustion
These factors combined cause about 7% of fatalities on high Himalayan peaks.
It’s common for many of these causes to co-occur–you get exhausted and have AMS, then you fall, or you’re exhausted and less able to take care of yourself and succumb to frostbite.
On Everest–as on any mountain–science, random chance, and human behavior all come together. Sometimes it results in summit success and a safe descent, and other times, in tragedy.