Mt. Everest has two main climbing routes, the southeast ridge from Nepal and the northeast ridge from Tibet, as well as many other less frequently climbed routes. Of the two main routes, the southeast ridge is technically easier and is the more frequently used route. It was the route used by Edmund Hillary and Tenzing Norgay in 1953 .
Most attempts are made during May before the summer monsoon season. As the monsoon season approaches, a change in the jet stream at this time pushes it northward, thereby reducing the average wind speeds high on the mountain. While attempts are sometimes made after the monsoons in September and October, when the jet stream is again temporarily pushed northward, the additional snow deposited by the monsoons and the less stable weather patterns (tail end of the monsoon) makes climbing extremely difficult.
The ascent via the southeast ridge begins with a trek to Base Camp at 5,380 m (17,700 ft) on the south side of Everest in Nepal. Climbing equipment and supplies are carried by yaks and Sherpas to Base Camp on the Khumbu Glacier.
From Camp I, climbers make their way up the Western Cwm to the base of the Lhotse face, where Camp II or Advanced Base Camp (ABC) is established at 6,500 m (21,300 ft). The Western Cwm is a flat, gently rising glacial valley, marked by huge lateral crevasses in the centre which prevent direct access to the upper reaches of the Cwm. Climbers are forced to cross on the far right near the base of Nuptse to a small passageway known as the “Nuptse corner”. The Western Cwm is also called the “Valley of Silence” as the topography of the area generally cuts off wind from the climbing route. The high altitude and a clear, windless day can make the Western Cwm unbearably hot for climbers.
From ABC, climbers ascend the Lhotse face on fixed ropes up to Camp III, located on a small ledge at 7,470 m (24,500 ft). From there, it is another 500 metres to Camp IV on the South Col at 7,920 m (26,000 ft). From Camp III to Camp IV, climbers are faced with two additional challenges: The Geneva Spur and The Yellow Band. The Geneva Spur is an anvil shaped rib of black rock named by the 1952 Swiss expedition. Fixed ropes assist climbers in scrambling over this snow covered rock band. The Yellow Band is a section of interlayered marble, phyllite, and semischist which also requires about 100 metres of rope for traversing it.
On the South Col, climbers enter the death zone. Climbers typically only have a maximum of two or three days they can endure at this altitude for making summit bids. Clear weather and low winds are critical factors in deciding whether to make a summit attempt. If weather does not cooperate within these short few days, climbers are forced to descend, many all the way back down to Base Camp.
From Camp IV, climbers will begin their summit push around midnight with hopes of reaching the summit (still another 1,000 metres above) within 10 to 12 hours. Climbers will first reach “The Balcony” at 8,400 m (27,600 ft), a small platform where they can rest and gaze at peaks to the south and east in the early light of dawn. Continuing up the ridge, climbers are then faced with a series of imposing rock steps which usually forces them to the east into waist deep snow, a serious avalanche hazard. At 8,750 m (28,700 ft), a small table-sized dome of ice and snow marks the South Summit.
From the South Summit, climbers follow the knife-edge southeast ridge along what is known as the “Cornice traverse” where snow clings to intermittent rock. This is the most exposed section of the climb. At the end of this traverse is an imposing 12 m (40 ft) rock wall called the “Hillary Step” at 8,760 m (28,740 ft).
Hillary and Tenzing were the first climbers to ascend this step and they did it with primitive ice climbing equipment and with ropes. Nowadays, climbers will ascend this step using fixed ropes previously set up by Sherpas. Once above the step, it is a comparatively easy climb to the top on moderately angled snow slopes–though the exposure on the ridge is extreme especially while traversing large cornices of snow. After the Hillary Step, climbers also must traverse a loose and rocky section that has a large entanglement of fixed ropes that can be troublesome in bad weather. Climbers will typically spend less than a half-hour on the “top of the world”
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