CLIMBING MOUNT EVEREST
In 1913 British explorer John Noel sneaked into Tibet, which was also closed at the time, and made a preliminary survey of the mountain’s northern approaches, where the topography is less varied than on the southern side. In 1921 the British began a major exploration of the north side of the mountain, led by George Leigh Mallory. Mallory’s expedition, and another that took place soon afterward, were unable to overcome strong winds, avalanches, and other hazards to reach the summit. In 1924 a third British expedition resulted in the disappearance of Mallory and a climbing companion only 240 m (800 ft) from the summit. More attempts were made throughout the 1930s and into the 1940s. Then, with the conquest of Tibet by China in the early 1950s, the region was closed to foreigners again and the northern approaches to the mountain were sealed off.