K2, at 8,611 metres (28,251 ft) above sea level, is the second-highest mountain on Earth, after Mount Everest.

It lies in the Karakoram range, in part in the Gilgit-Baltistan region of Pakistan-administered Kashmir and in part in a China-administered territory of the Kashmir region included in the Taxkorgan Tajik Autonomous County of Xinjiang.

K2 also became popularly known as the Savage Mountain after George Bell—a climber on the 1953 American Expedition—told reporters, “It’s a savage mountain that tries to kill you.” Of the five highest mountains in the world, K2 is the deadliest; approximately one person dies on the mountain for every four who reach the summit. Also occasionally known as Chhogori, or Mount Godwin-Austen, other nicknames for K2 are The King of Mountains and The Mountaineers’ Mountain, as well as The Mountain of Mountains after prominent Italian climber Reinhold Messner titled his book about K2 the same.

The summit was reached for the first time by the Italian climbers Lino Lacedelli and Achille Compagnoni, on the 1954 Italian Expedition led by Ardito Desio. In January 2021, K2 became the final eight-thousander to be summited in the winter; the mountaineering feat was accomplished by a team of Nepalese climbers, led by Nirmal Purja and Mingma Gyalje Sherpa.

K2 is the only 8,000+ metre peak that has never been climbed from its eastern face. Ascents have almost always been made in July and August, which are typically the warmest times of the year; K2’s more northern location makes it more susceptible to inclement and colder weather.The peak has now been climbed by almost all of its ridges. Although the summit of Everest is at a higher altitude, K2 is a more difficult and dangerous climb, due in part to its more inclement weather. As of June 2018, only 367 people have completed the ascent to its summit. There have been 91 deaths during attempted climbs, according to the list maintained on the list of deaths on eight-thousanders.

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, labelling them K1 and K2, where the K stands for Karakoram.

The policy of the Great Trigonometrical 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”) has been suggested as a local name,[20] 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.

With the mountain lacking a local name, the name Mount Godwin-Austen was suggested, in honour 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 (Balti: کے چو‎ 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.”

Geographical setting
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 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 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 then the claim that K2 was the tallest mountain in the world had already made it into many news reports and reference works.

The height of K2 given on maps and encyclopedias is 8,611 metres (28,251 ft). In the summer of 2014, a Pakistani-Italian expedition to K2, named “K2 60 Years Later”, was organized to commemorate the 60th anniversary of the first ascent of K2. One of the goals of the expedition was to accurately measure the height of the mountain using satellite navigation. The height of K2 measured during this expedition was 8,609.02 metres (28,244.8 ft).

The mountains of K2 and Broad Peak, and the area westward to the lower reaches of Sarpo Laggo glacier, consist of metamorphic rocks, known as the K2 Gneiss, and part of the Karakoram Metamorphic Complex. The K2 Gneiss consists of a mixture of orthogneiss and biotite-rich paragneiss. On the south and southeast face of K2, the orthogneiss consists of a mixture of a strongly foliated plagioclase-hornblende gneiss and a biotite-hornblende-K-feldspar orthogneiss, which has been intruded by garnet-mica leucogranitic dikes. In places, the paragneisses include clinopyroxene-hornblende-bearing psammites, garnet (grossular)-diopside marbles, and biotite-graphite phyllites. Near the memorial to the climbers who have died on K2, above Base Camp on the south spur, thin impure marbles with quartzites and mica schists, called the Gilkey-Puchoz sequence, are interbanded within the orthogneisses. On the west face of Broad Peak and south spur of K2, lamprophyre dikes, which consist of clinopyroxene and biotite-porphyritic vogesites and minettes, have intruded the K2 gneiss. The K2 Gneiss is separated from the surrounding sedimentary and metasedimentary rocks of the surrounding Karakoram Metamorphic Complex by normal faults. For example, a fault separates the K2 gneiss of the east face of K2 from limestones and slates comprising nearby Skyang Kangri.

Argon Dating ages of 115 to 120 million years ago obtained from and geochemical analyses of the K2 Gneiss demonstrate that it is a metamorphosed, older, Cretaceous, pre-collisional granite. The granitic precursor (protolith) to the K2 Gneiss originated as the result of the production of large bodies of magma by a northward-dipping subduction zone along what was the continental margin of Asia at that time and their intrusion as batholiths into its lower continental crust. During the initial collision of the Asia and Indian plates, this granitic batholith was buried to depths of about 20 kilometres (12 mi) or more, highly metamorphosed, highly deformed, and partially remelted during the Eocene Period to form gneiss. Later, the K2 Gneiss was then intruded by leucogranite dikes and finally exhumed and uplifted along major breakback thrust faults during post-Miocene time. The K2 Gneiss was exposed as the entire K2-Broad Peak-Gasherbrum range experienced rapid uplift with which erosion rates have been unable to keep pace.