Everyone has seen the Everest traffic jam photo, this is what standing in that line actually does to you

In the spring of 2019 a record number of climbers were funnelled onto Mount Everest during only two good-weather days, and the result was a queue of hundreds of people strung along the summit ridge in the “death zone” above 8,000 m. Eleven people died on the mountain that season. The photograph of that human traffic jam went around the world — but what the picture does not show is the slow, invisible thing a queue does to a body up there. On Everest the crowd itself can be the danger, not just the mountain.

The photo that went around the world

On 22 May 2019 the Nepali mountaineer Nirmal “Nims” Purja photographed a dense, unbroken line of climbers snaking up the final ridge toward the Hillary Step and the summit. He later said there were roughly 320 people on the mountain that morning. The image landed on the front pages of the world’s newspapers because it punctured a myth: the top of the highest mountain on Earth, that day, looked like a rush-hour footpath. More than 200 people are thought to have reached the summit in that single window, and climbers reported waiting in the cold for two hours or more to pass the bottleneck below the top.

Why a queue is lethal up there

The summit of Everest sits in what climbers call the death zone — the altitude above roughly 8,000 m where there is too little oxygen to sustain human life for long, even with bottled gas. A climber’s body is deteriorating every hour: judgement blurs, muscles fail, and the risk of a fatal high-altitude brain or lung oedema climbs steeply. The plan that keeps people alive is speed — up and down through the death zone as fast as possible. A traffic jam destroys that plan. Every extra hour spent standing still burns finite bottled oxygen, and a climber who runs out high on the ridge is suddenly breathing air that cannot keep them conscious. The cold does the rest: motionless in a queue, with no exertion to generate heat, exposed fingers and toes freeze and frostbite sets in. This is also why the descent is so deadly — climbers reach the top late, spent and out of gas, then must reverse the whole exposed route, which is when many high-altitude deaths happen.

What actually caused the jam

The crowd was the visible cause, but it was the product of three things stacking up. First, Nepal issued a record 381 permits and did not cap numbers. Second, the rope-fixing to the summit was completed late and the weather refused to cooperate, leaving only a sliver of a window. Third, when that window opened, every team on the mountain went for it at once — because the alternative was to wait for a window that might never come. Put those together and you get hundreds of people trying to pass through a single knife-edge of rock at the same time, at an altitude where you cannot afford to wait. The mountain did not change in 2019. The management of the people on it did. We explain the counter-intuitive detail — that more climbers die coming down Everest than going up — and how thin the air really is in our guide to altitude sickness, AMS, HACE and HAPE.

Cover photo: Bijay Chaurasia via Wikimedia Commons (CC BY-SA 4.0).