A chilling photo of dozens of climbers making their way up Mount Everest shows a deadly traffic jam at 30,000 feet.
Mountaineering experts believe a similar bottleneck at the Hillary Step, a 40-foot rock wall at 28,740 feet, was at least partially responsible for the deaths of four climbers last weekend.
Ha Wenyi, 55, from China, Canadian Shriya Shah-Klorfine, 32, German Eberhard Schaaf, 61, and 44-year-old Song Won-bin from South Korea were all stopped nearly three hours at the dizzying altitude -- forced to burn up their precious oxygen supplies as they waited for a crowd of 150 climbers to clear the area.
Bottleneck: Dozens of climbers form a long line headed up Mount Everest as they try to take advantage of a small window of good weather on the mountain
Crowded: Climbing experts believe the 150 people who mobbed a pass in the mountain caused a backlog that contributed to the deaths of four people
The photo, taken by Ralf Dujmovits for Outside Magazine, is a stark portrait of just how crowded the world's highest peak has become -- loaded with mostly amateur climbers paying sherpas to do much of the hard work for them.
Treacherous weather on the unforgiving mountain clears up only for a short time, leaving small windows of opportunity for dozens of climbers to attempt the summit.
Most of these men and women are desperate to get a return on the $75,000 they've paid for the privilege to climb up Everest.
Many of the 220 people who was died on Everest were amateurs who pressed forward against the advice of their sherpas or other climbers.
Casualties: German doctor Eberhard Schaaf, left, and Nepalese-Canadian Shriya Shah-Klorfine were among those found. According to a friend, Shah's last words were 'Save me'
Ms Shah-Klorfine appears to have ignored both, according to Outside.
When two climbers reached her on the way back from the summit, they noticed that she was acting strangely.
They urged her to turn back. She shook her head and motioned aggressively forward.
Eventually her sherpas urged her to turn around, too.