K2

K2 also known as Mount Godwin-Austen or Chhogori is the second highest mountain in the world, after Mount Everest, at 8,611 metres (28,251 ft) above sea level. It is located on the China-Pakistan border between Baltistan, in the Gilgit-Baltistan region of northern Pakistan, and the 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.

K2 is known as the Savage Mountain due to the extreme difficulty of ascent. It has the second-highest fatality rate among the eight thousanders. With around 300 successful summits and 77 fatalities, about one person dies on the mountain for every four who summit. It is more difficult and hazardous to reach the peak of K2 from the Chinese side, so it is usually climbed from the Pakistani side. Unlike Annapurna, the mountain with the highest fatality-to-summit rate (191 summits and 61 fatalities), or the other eight thousanders, K2 has never been climbed during winter.

The name K2 is derived from the notation used by the Great Trigonometric Survey of British India. Thomas Montgomerie made the first survey of the Karakoram from Mount Haramukh, some 210 km (130 miles) to the south, and sketched the two most prominent peaks, labeling them K1 and K2.

The policy of the Great Trigonometric Survey was to use local names for mountains wherever possible and K1 was found to be known locally as Masherbrum. K2, however, appeared not to have acquired a local name, possibly due to its remoteness. The mountain is not visible from Askole, the last village to the south, or from the nearest habitation to the north, and is only fleetingly glimpsed from the end of the Baltoro Glacier, beyond which few local people would have ventured.

The name Chogori, derived from two Balti words, chhogo ("big") and ri ("mountain") (چھوغوری) has been suggested as a local name, but evidence for its widespread use is scant. It may have been a compound name invented by Western explorers or simply a bemused reply to the question "What's that called?" It does, however, form the basis for the name Qogir (simplified Chinese: 乔戈里峰; traditional Chinese: 喬戈里峰; pinyin: Qiáogēlǐ Fēng) by which Chinese authorities officially refer to the peak. Other local names have been suggested including Lamba Pahar ("Tall Mountain" in Urdu) and Dapsang, but are not widely used.

Lacking a local name, the name Mount Godwin-Austen was suggested, in honor of Henry Godwin-Austen, an early explorer of the area. While the name was rejected by the Royal Geographical Society, it was used on several maps, and continues to be used occasionally.

The surveyor's mark, K2, therefore continues to be the name by which the mountain is commonly known. It is now also used in the Balti language, rendered as Kechu or Ketu (Urdu: کے ٹو‎). The Italian climber Fosco Maraini argued in his account of the ascent of Gasherbrum IV that while the name of K2 owes its origin to chance, its clipped, impersonal nature is highly appropriate for so remote and challenging a mountain. He concluded that it was:

... just the bare bones of a name, all rock and ice and storm and abyss. It makes no attempt to sound human. It is atoms and stars. It has the nakedness of the world before the first man – or of the cindered planet after the last.

Andre Weil named K3 surfaces in mathematics partly after the mountain 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.

K2 is merely ranked 22nd by topographic prominence, a measure of a mountain's independent stature, because it is part of the same extended area of uplift (including the Karakoram, the Tibetan Plateau, and the Himalaya) as Mount Everest, in that it is possible to follow a path from K2 to Everest that goes no lower than 4,594 metres (15,072 ft), at the Kora La on the Nepal/China border in the Mustang Lo. Many other peaks that are far lower than K2 are more independent in this sense. It is, however, the most prominent peak within the Karakoram range.

K2 is notable for its local relief as well as its total height. It stands over 3,000 metres (9,840 ft) above much of the glacial valley bottoms at its base. It is a consistently steep pyramid, dropping quickly in almost all directions. The north side is the steepest: there it rises over 3,200 metres (10,500 ft) above the K2 (Qogir) Glacier in only 3,000 metres (9,800 ft) of horizontal distance. In most directions, it achieves over 2,800 metres (9,200 ft) of vertical relief in less than 4,000 metres (13,000 ft).

A 1986 expedition led by George Wallerstein made an inaccurate measurement incorrectly showing that K2 was taller than Mount Everest, and therefore the tallest mountain in the world. A corrected measurement was made in 1987, but by that point the claim that K2 was the tallest mountain in the world had already made it into many news reports and reference works.