Not far above Base Camp, the constantly changing maze of giant ice blocks (seracs) and deep cracks (crevasses) of the icefall is one of the most dangerous parts of the route to Everest's summit.
At the start of every climbing season Sherpas slowly work through the icefall to scout out a route and put in place ropes and aluminium ladders to assist the climbers move over the crevasses. However, despite the Sherpas picking the safest way through, the Khumbu icefall is still a dangerous place to be.
As the huge mass of ice slides down from the Western Cwm into the Khumbu Valley, blocks of ice the size of houses come crashing down from above and new crevasses hundreds of feet deep can crack open at any moment. With 19 fatalities, more climbers have died in the ice of the Khumbu than on any other part of the mountain making it the deadliest place on Everest.
The Khumbu Icefall must be crossed each time a climber wishes to move between Base Camp and higher on the mountain. Depending on the number of acclimatisation climbs it is not uncommon for climbers to pass back and forth through the icefall up to twelve times (six return journeys) during the expedition.