Editing K2 (section)

==Climbing routes and difficulties==

K2 features several routes, each with distinct characteristics; however, they all share common challenges. The first is the extreme altitude, which results in a significant reduction in available oxygen. At the summit of K2, only one-third of the oxygen present at sea level is available to climbers.<ref name=alt_calc/> The second challenge is the mountain’s tendency to experience extreme storms lasting several days, which have resulted in many of the deaths on the peak. The third is the steep, exposed, and demanding nature of all routes on the mountain, which makes retreat particularly difficult, especially during storms. Despite numerous attempts, the first successful winter ascent occurred only in 2021. All major climbing routes are located on the Pakistani side.{{citation needed|date=January 2021}} The base camp is also located on the Pakistani side.<ref>{{Cite web|last=Watson|first=Peter|date=January 12, 2021|title=Trekking to K2 base camp in Pakistan: everything you need to know|url=https://www.lonelyplanet.com/articles/how-to-trek-to-k2-base-camp|website=Lonely Planet}}</ref>

===<span id="Abruzzi Spur"></span><span id="Abruzzi Ridge"></span>Abruzzi Spur===
[[File:K2_Abruzzi_Spur.jpg|thumb|right|The south side of K2 with the Abruzzi Spur route]]
The standard route of ascent, used by 75% of all climbers, is the Abruzzi Spur,<ref name="him_alpine_style"/><ref name="world_mountaineering"/> located on the Pakistani side, [[#Notable2|first attempted]] by [[Prince Luigi Amedeo, Duke of the Abruzzi]] in 1909. This is the peak's southeast ridge, rising above the [[Godwin-Austen Glacier]]. The spur proper begins at an altitude of {{convert|5400|m|ft}}, where Advanced Base Camp is usually placed. The route follows an alternating series of rock ribs, snow/ice fields, and some technical [[rock climbing]] on two famous features, "[[House's Chimney]]" and the "Black Pyramid." Above the Black Pyramid, the route continues along dangerously exposed and difficult-to-navigate slopes leading to the easily visible "Shoulder" and then on to the summit.  The last major obstacle is a narrow [[couloir]] known as the "[[Bottleneck (K2)|Bottleneck]]", which places climbers dangerously close to a wall of [[serac]]s that form an ice cliff to the east of the summit. It was partly due to the collapse of one of these seracs around 2001 that no climbers reached the summit in 2002 and 2003.<ref name="aaj_2005"/>

Between 1 and 2 August 2008, 11 climbers from several expeditions died during [[2008 K2 disaster|a series of accidents]], including several icefalls in the Bottleneck.<ref name=cnn_2008_0803/><ref name=bbc_2008_0803/>

===North Ridge===
[[File:K2 Nordseite.jpg|thumb|right|The north side of K2. The North Ridge is in the centre of the picture.]]
Almost opposite the Abruzzi Spur is the North Ridge,<ref name="him_alpine_style"/><ref name="world_mountaineering"/> which ascends the Chinese side of the peak. It is rarely climbed, partly due to very difficult access, involving crossing the [[Shaksgam River]], which is a hazardous undertaking.<ref name="aaj_1991"/> In contrast to the crowds of climbers and trekkers at the Abruzzi basecamp, usually at most two teams are encamped below the North Ridge. This route, more technically difficult than the Abruzzi,{{Citation needed|date=December 2020}} ascends a long, steep, primarily rock ridge to high on the mountain—Camp IV, the "Eagle's Nest" at {{convert|7900|m|ft}}—and then crosses a dangerously slide-prone [[hanging glacier]] by a leftward climbing traverse, to reach a snow couloir which accesses the summit.{{citation needed|date=January 2021}}

Besides the [[#Notable1|original Japanese ascent]], a notable ascent of the North Ridge was the one in 1990 by Greg Child, Greg Mortimer, and [[Steve Swenson]], which was done [[alpine style]] above Camp 2, though using some [[fixed rope]]s already put in place by a Japanese team.<ref name="aaj_1991"/>

===Other routes===
[[File:K2-Northwestface.jpg|thumb|right|The routes climbed on the Northwest of the mountain. A: West Ridge; B: West Face; C: Northwest Ridge; D: North Ridge; E: Northeast Ridge.]]
[[File:K2 south routes.svg|thumb|right|The routes climbed on the southern side of the mountain. A: West Ridge; B; West Face (behind mountain); C: Southwest Pillar ("Magic Line"); D: South Face ("Polish Line"/"Central Rib"); E: South-southeast Spur ("Cesen route"/"Basque route"); F: Abruzzi Spur.]]
Because 75% of people who climb K2 use the Abruzzi Spur, these listed routes are rarely climbed. No one has climbed the East Face of the mountain due to the instability of the snow and ice formations on that side.<ref>{{Cite web|url=https://explorersweb.com/2019/01/28/winter-8000ers-update-gale-on-manaslu-east-face-of-k2-impossible/|title = Winter 8000'ers Update: Gale on Manaslu, East Face of K2 "Impossible"|date = 28 January 2019}}</ref> In addition to the East Face, the North Face has not yet been climbed either. In 2007, [[Denis Urubko]] and Serguey Samoilov intended to climb the K2's North Face but they were stymied by increasingly deteriorating conditions. After finding their intended route menaced by growing avalanche danger, they traversed onto the normal North Ridge route and summited on 2 October 2007, making the latest summer season ascent of the peak in history.<ref>{{cite web |url=http://www.alpinist.com/doc/web07f/newswire-kazakhs-k2 |title=Kazakhs Make Latest Season Ascent of K2 in History |work=Alpinist |last=Bauer |first=Luke |date=4 October 2007 |access-date=26 August 2021 }}</ref>

;Northeast Ridge: Long and marked with the presence of multiple ice cornices, this ridge finishes on the uppermost part of Abruzzi route. First crossed by a Polish expedition led by [[Janusz Kurczab]] in 1976. The team was not able to summit due to poor weather.<ref name=thj_1979/> First climbed by Louis Reichardt and James Wickwire on 6 September 1978.<ref>{{Cite web |url=https://www.rei.com/blog/climb/the-first-american-ascent-k2 |title = 40 Years Later: The Story Behind the First American Ascent of K2 |date = 18 October 2018}}</ref>

; West Ridge: First climbed in 1981 by a Japanese team.<ref name=aaj_1992_K2_West/> This route starts on the distant Negrotto Glacier and goes through unpredictable bands of rock and snowfields.{{citation needed|date=January 2021}}

; Southwest Pillar or "Magic Line": Very technical, and the second most demanding. First climbed in 1986 by the Polish-Slovak trio Piasecki-Wróż-Božik. Since then Jordi Corominas from Spain has been the only successful climber on this route (he summited in 2004),<ref name=BaseCamp/> despite many other attempts.{{citation needed|date=January 2021}}

; South Face or "Polish Line" or "Central Rib": Extremely exposed, demanding, and dangerous. In July 1986, [[Jerzy Kukuczka]] and [[Tadeusz Piotrowski (mountaineer)|Tadeusz Piotrowski]] summited on this route. Piotrowski was killed while descending on the Abruzzi Spur. The route starts off the first part of the Southwest Pillar and then deviates into a totally exposed, snow-covered cliff area, then through a gully known as "the Hockey Stick", and then up to yet another exposed cliff face, continuing through yet another extremely exposed section all the way up to the point where the route joins with the Abruzzi Spur about {{cvt|1000|ft|order=flip||}} before the summit. [[Reinhold Messner]] called it a suicidal route and so far, no one has repeated Kukuczka and Piotrowski's achievement. "The route is so avalanche-prone, that no one else has ever considered a new attempt."<ref name=Messner1982/><ref>{{cite web|url=http://www.k2climb.net/expguide/route.htm|title=The Route – Climbers guide to K2|website=www.k2climb.net|access-date=23 October 2017}}</ref>

; Northwest Face: First ascent via this route was in 1990 by a Japanese team; this route is located on the Chinese side of the mountain. This route is known for its chaotic rock and snowfields all the way up to the summit.<ref name=BaseCamp/>

; Northwest Ridge: First climbed in 1991 by a French team: Pierre Beghin and Christophe Profit. Finishes on North Ridge. The second attempt in 1995 by an American team, they reached {{cvt|8100|m|ft}} on 2 August before turning back in deteriorating weather.<ref>{{Cite web|url=http://publications.americanalpineclub.org/articles/12199628602/Asia-Pakistan-K2-Northwest-Ridge-Attempt|title = AAC Publications – Asia, Pakistan, K2, Northwest Ridge Attempt}}</ref>

; South-southeast spur or "Cesen route" or "Basque route": It runs the pillar between the Abruzzi Spur and the Polish Route. It connects with the Abruzzi Spur on the Shoulder, above the Black Pyramid and below the Bottleneck; since it avoids the Black Pyramid, it is considered safer. In 1986, [[Tomo Česen]] ascended to {{cvt|8000|m|||}} via this route. The first summit via this route was by a Basque team in 1994.<ref name=BaseCamp>{{cite web|url=https://basecampmagazine.com/2017/06/09/routes-up-to-k2s-summit/|title=Routes Up to K2's Summit|date=9 June 2017|first=CJ|last=Leger|publisher=Base Camp Magazine}}</ref>

; West Face: Technical difficulty at high altitude, first climbed by a Russian team in 2007.<ref name=RussianClimb_2007/> This route is almost entirely made up of rock crevasses and snow-covered couloirs.<ref name=BaseCamp/> In 2024, Japanese climbers [[Kazuya Hiraide]] and [[Kenro Nakajima]] were lost in attempting a new line on this route.<ref name="Annapurna"/>

===Use of supplemental oxygen===
For most of its climbing history, K2 was not usually climbed with supplemental oxygen. Small, lightweight teams were the norm.<ref name="him_alpine_style">{{cite book |last1=Fanshawe |first1=Andy |last2=Venables |first2=Stephen|title=Himalaya Alpine-Style |publisher= Hodder and Stoughton |date= 1995 |isbn=0-340-64931-3}}</ref><ref name="world_mountaineering">{{cite book |editor-last=Salkeld |editor-first=Audrey |title=World Mountaineering |publisher=Bulfinch Press|year= 1998 |isbn=0-8212-2502-2}}</ref> However, the 2004 season saw a great increase in the use of oxygen: 28 of 47 summiteers used oxygen in that year.<ref name="aaj_2005"/>

Acclimatisation is essential when climbing without oxygen to avoid some degree of [[altitude sickness]].<ref name=Acclimatisation/>
K2's summit is well above the altitude at which [[high-altitude pulmonary edema]] (HAPE) and [[high-altitude cerebral edema]] (HACE) can occur.<ref name=MedicalProblems/> In [[mountaineering]], when ascending above an altitude of {{convert|8000|m|ft}}, the climber enters what is known as the ''[[death zone]]''.<ref>{{cite web |last1=Woodward |first1=Aylin |title=What happens to your body in Mount Everest's 'death zone,' where 11 people have died in the past week |url=https://www.businessinsider.com/mount-everest-death-zone-what-happens-to-body-2019-5 |website=Business Insider |access-date=4 November 2022}}</ref>