Ice entering the fall takes approximately 4.3 years to emerge at the base, which is 600 metres (2,000 ft) lower and 1.5 kilometres (1 mi) away horizontally.
Crossing the Khumbu Icefall is so dangerous that even extensive rope and ladder networks installed by professional guides cannot prevent loss of life.
Prudent climbers place emphasis on avalanche and crevasse-fall survival and rescue techniques prior to entering this terrain.
As sunlight warms the area, ice-melt causes friction within the structure to decline, which increases the rate of flow and hence, crevasse opening and ice-block or serac collapse.
They were assisting in the production of the Canadian documentary The Man Who Skied Down Everest, featuring Japanese alpinist Yūichirō Miura.