Climbing routes of mount everest

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.[28] 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 and the first recognised of fifteen routes to the top by 1996.[28] This was, however, a route decision dictated more by politics than by design as the Chinese border was closed to western world in 1950s after the Communist China took over the control Tibet from the Republic of China.[29]

View from space showing South Col route and North Col/Ridge route
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.[30][31] 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 more difficult.

Southeast ridge
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. Expeditions usually fly into Lukla (2,860 m) from Kathmandu and pass through Namche Bazaar. Climbers then hike to Base Camp, which usually takes six to eight days, allowing for proper altitude acclimatization in order to prevent altitude sickness. Climbing equipment and supplies are carried by yaks, dzopkyos (yak hybrids) and human porters to Base Camp on the Khumbu Glacier. When Hillary and Tenzing climbed Everest in 1953, they started from Kathmandu Valley, as there were no roads further east at that time.
Climbers will spend a couple of weeks in Base Camp, acclimatizing to the altitude. During that time, Sherpas and some expedition climbers will set up ropes and ladders in the treacherous Khumbu Icefall. Seracs, crevasses and shifting blocks of ice make the icefall one of the most dangerous sections of the route. Many climbers and Sherpas have been killed in this section. To reduce the hazard, climbers will usually begin their ascent well before dawn when the freezing temperatures glue ice blocks in place. Above the icefall is Camp I at 6,065 metres (19,900 ft).
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 relatively 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.[32]
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 a 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.[32]
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.

A view of Everest southeast ridge base camp. The Khumbu Icefall can be seen in the left. In the center are the remains of a helicopter that crashed in 2003.
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 dawn light. 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.[32]
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 as a misstep to the left would send one 2,400 m (8,000 ft) down the southwest face while to the immediate right is the 3,050 m (10,000 ft) Kangshung face. 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).[32]
Hillary and Tenzing were the first climbers to ascend this step and they did it with primitive ice climbing equipment and without fixed 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 very large cornices of snow. With increasing numbers of people climbing the mountain in recent years, the Step has frequently become a bottleneck, with climbers forced to wait significant amounts of time for their turn on the ropes, leading to problems in getting climbers efficiently up and down the mountain. After the Hillary Step, climbers also must traverse a very loose and rocky section that has a very large entanglement of fixed ropes that can be troublesome in bad weather. Climbers will typically spend less than a half-hour on "top of the world" as they realize the need to descend to Camp IV before darkness sets in, afternoon weather becomes a serious problem, or supplemental oxygen tanks run out.

Northeast ridge

Everest North Face, Tibet
The northeast ridge route begins from the north side of Everest in Tibet. Expeditions trek to the Rongbuk Glacier, setting up Base Camp at 5,180 m (16,990 ft) on a gravel plain just below the glacier. To reach Camp II, climbers ascend the medial moraine of the east Rongbuk Glacier up to the base of Changtse at around 6,100 m (20,000 ft). Camp III (ABC - Advanced Base Camp) is situated below the North Col at 6,500 m (21,300 ft). To reach Camp IV on the north col, climbers ascend the glacier to the foot of the col where fixed ropes are used to reach the North Col at 7,010 m (23,000 ft). From the North Col, climbers ascend the rocky north ridge to set up Camp V at around 7,775 m (25,500 ft). The route crosses the North Face in a diagonal climb to the base of the Yellow Band reaching the site of Camp VI at 8,230 m (27,000 ft). From Camp VI, climbers will make their final summit push. Climbers face a treacherous traverse from the base of the First Step: 27,890 feet - 28,000 feet, to the crux of the climb, the Second Step: 28,140 feet - 28,300 feet. (The Second Step includes a climbing aid called the "Chinese ladder", a metal ladder placed semi-permanently in 1975 by a party of Chinese climbers. It has been almost continuously in place since, and is used by virtually all climbers on the route.) Once above the Second Step the inconsequential Third Step is clambered over: 28,510 feet - 28,870 feet. Once above these steps, the summit pyramid is climbed by means of a snow slope of 50 degrees, to the final summit ridge along which the top is reached.[33]