K2, at 8,611 metres (28,251 ft) above sea level, is the second highest mountain in the world, after Mount Everest at 8,848 metres (29,029 ft). It is located on the China–Pakistan border between Baltistan in the Gilgit-Baltistan region of northern Pakistan, and Dafdar Township in Taxkorgan Tajik Autonomous County of Xinjiang, China. K2 is the highest point of the Karakoram range and the highest point in both Pakistan and Xinjiang.
The name K2 is derived from the notation used by the Great Trigonometrical Survey of British India. Thomas Montgomerie made the first survey of the Karakoram from Mount Haramukh, some 210 km (130 mi) to the south, and sketched the two most prominent peaks, labeling them K1 and K2.
K2 lies in the northwestern Karakoram Range. It is located in the Baltistan region of Gilgit–Baltistan, Pakistan, and the Taxkorgan Tajik Autonomous County of Xinjiang, China. The Tarim sedimentary basin borders the range on the north and the Lesser Himalayas on the south. Melt waters from vast glaciers, such as those south and east of K2, feed agriculture in the valleys and contribute significantly to the regional fresh-water supply.
The mountain was first surveyed by a European survey team in 1856. Team member Thomas Montgomerie designated the mountain "K2" for being the second peak of the Karakoram range. The other peaks were originally named K1, K3, K4, and K5, but were eventually renamed Masherbrum, Gasherbrum IV, Gasherbrum II, and Gasherbrum I, respectively. In 1892, Martin Conway led a British expedition that reached "Concordia" on the Baltoro Glacier.
There are a number of routes on K2, of somewhat different character, but they all share some key difficulties, the first being the extremely high altitude and resulting lack of oxygen: there is only one-third as much oxygen available to a climber on the summit of K2 as there is at sea level. The second is the propensity of the mountain to experience extreme storms of several days duration, which have resulted in many of the deaths on the peak. The third is the steep, exposed, and committing nature of all routes