<P> 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 . </P> <P> 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). </P> <P> 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 . </P> <P> On the South Col, climbers enter the death zone . Climbers making summit bids typically can endure no more than two or three days at this altitude . That's one reason why clear weather and low winds are critical factors in deciding whether to make a summit attempt . If the weather does not cooperate within these short few days, climbers are forced to descend, many all the way back down to Base Camp . </P>

Mount everest the tallest mountain in the world