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The Khumbu Icefall is located at the head of the Khumbu Glacier and the foot of the Western Cwm, which lies at an altitude of 5,486 metres (17,999 ft) on the Nepali slopes of Mount Everest, not far above Base Camp and southwest of the summit. The icefall is considered one of the most dangerous stages of the South Col route to Everest's summit.
The Khumbu Glacier forming the icefall moves an estimated 0.9 to 1.2 m (3 to 4 ft) down the mountain every day, a speed that opens large crevasses with little warning and suddenly collapses large towers of ice (called seracs), ranging in size that of cars to large houses, that tumble down the glacier from time to time.
Most climbers try to cross before sunrise when the icefall, still partially frozen from nighttime cold, is less able to move. As intense sunlight warms the area, friction within the ice structure declines, which increases the rate of crevasses opening and blocks of snow and ice falling. The most dangerous time to cross is generally mid- to late-afternoon.
Strong, acclimatized climbers can ascend the icefall in a few hours, while climbers who go through it for the first time, or lack acclimatization or experience, tend to complete the journey in 10–12 hours. "Camp I" on Everest's South Col route is typically slightly beyond the top of the Khumbu Icefall.
On occasion, a large block of ice crashes down in the vicinity of a climber, producing a blast of displaced air and snow that can result in a "dusting" from a billowing cloud of light ice and snow—a very unnerving experience. A climber caught in an avalanche or other "movement" event in the icefall can do very little because it is not possible to run away or even to know which direction to run; therefore, climbers train for entrapment by heavy blocks of ice as well as rescuing others.
Since the structures are continually changing, crossing the Khumbu Icefall is so dangerous that even extensive rope and ladder crossings cannot prevent loss of life. Many people have died in this area, such as a climber crushed by a 12-story block of ice. Exposed crevasses may be easy to avoid, but some may be hidden under dangerous snow bridges through which unwary climbers can fall.
Around 6:30 am local time on 18 April 2014, 16 Nepalese climbers were killed by an avalanche in the Khumbu Icefall. Only 13 bodies were recovered. Nine others sustained blunt trauma injuries. The climbers were preparing the route through the dangerous icefall for the spring climbing season when the avalanche engulfed them.
- UNITEC Institute of Technology. "Hillary Challenge". Ministry of Education, Wellington, New Zealand. Archived from the original on 2008-09-06.
- "Mount Everest avalanche kills 12 Nepalese guides". CBC News. 18 April 2014. Retrieved 2014-03-18.
- Krakauer, Jon (21 April 2014). "Death and Anger on Everest". The New Yorker. Retrieved 22 April 2014.
Of the twenty-five men hit by the falling ice, sixteen were killed, all of them Nepalis working for guided climbing teams.
- Burke, Jason; Rauniyar, Ishwar (18 April 2014). "Mount Everest avalanche leaves at least 12 Nepalese climbers dead". The Guardian. Retrieved 2014-03-18.