Mountaineering or alpinism is the set of activities that involves traversing mountainous terrain. This terrain, constituting both natural and man-made landscapes, contains steep slopes that may be rocky or covered with ice and snow.^[2] The classic mountaineering activity is ascending summits; this is often referred to as peak bagging.^[3] Today, the sport encompasses a wide variety of disciplines and endeavors, each requiring various degrees of experience, athletic ability, and technical knowledge.^[4] Recreational climbing, skiing, and snow travel are the disciplines most intricately linked to mountaineering.^[5] Hiking, camping, and navigation are also a major part of the sport.^[4] At its highest level, it is one of the extreme sports, among which it is sometimes cited as an archetypal example.^[6][7]

Unlike most sports, mountaineering lacks widely-applied formal rules, regulations, and governance; mountaineers adhere to a large variety of techniques and philosophies when climbing mountains.^[2] Numerous local alpine clubs support mountaineers by hosting resources and social activities. A federation of alpine clubs, the International Climbing and Mountaineering Federation (UIAA), is the International Olympic Committee-recognized world organization for mountaineering and climbing. It can also be categorized as dangerous but a motivational one.^[8]

Humans have been present in mountains since prehistory. The remains of Ötzi, who lived in the 4th millennium BC, were found in a glacier in the Ötztal Alps.^[9] However, the highest mountains were rarely visited early on, and were often associated with supernatural or religious concepts.^[5] Nonetheless, there are many documented examples of people climbing mountains prior to the formal development of the sport in the 19th century, although many of these stories are sometimes considered fictional or legendary.

The famous poet Petrarch describes his 26 April 1336 ascent of Mount Ventoux (1,912 m (6,273 ft)) in one of his epistolae familiares, claiming to be inspired by Philip V of Macedon's ascent of Mount Haemo.^[10][11]

For most of antiquity, climbing mountains was a practical or symbolic activity, usually undertaken for economic, political, or religious purposes.

A commonly cited example is the 1492 ascent of Mont Aiguille (2,085 m (6,841 ft)) by Antoine de Ville, a French military officer and lord of Domjulien and Beaupré. This expedition was a military exercise involving a team using ladders and ropes. King Louis XIV ordered its ascent to assert national sovereignty and his rule of France.^[11]

The Age of Enlightenment marked a change of attitudes towards high mountains. In 1757 Swiss scientist Horace-Bénédict de Saussure made the first of several unsuccessful attempts on Mont Blanc in France. He then offered a reward to anyone who could climb the mountain, which was claimed in 1786 by Jacques Balmat and Michel-Gabriel Paccard. The climb is usually considered an epochal event in the history of mountaineering, a symbolic mark of the birth of the sport.^[5][11]

By the early 19th century, many of the alpine peaks were reached, including the Grossglockner in 1800, the Ortler in 1804, the Jungfrau in 1811, the Finsteraarhorn in 1812, and the Breithorn in 1813.^[5] In 1808, Marie Paradis became the first woman to climb Mont Blanc, followed in 1838 by Henriette d'Angeville.^[12]

The beginning of mountaineering as a sport in the UK is generally dated to the ascent of the Wetterhorn in 1854 by English mountaineer Sir Alfred Wills, who made mountaineering fashionable in Britain. This inaugurated what became known as the Golden Age of Alpinism, with the first mountaineering club - the Alpine Club - being founded in 1857.^[13][14]

One of the most dramatic events was the spectacular first ascent of the Matterhorn in 1865 by a party led by English illustrator Edward Whymper, in which four of the party members fell to their deaths. By this point the sport of mountaineering had largely reached its modern form, with a large body of professional guides, equipment, and methodologies.^[11]

In the early years of the "golden age", scientific pursuits were intermixed with the sport, such as by the physicist John Tyndall. In the later years, it shifted to a more competitive orientation as pure sportsmen came to dominate the London-based Alpine Club and alpine mountaineering overall.^[15]

In the 19th century, the focus of mountaineering turned towards mountains beyond the Alps, and by the turn of the 20th century, mountaineering had acquired a more international flavour.^[16]

In 1897 Mount Saint Elias (18,008 ft (5,489 m)) on the Alaska-Yukon border was summitted by the Duke of the Abruzzi and party. ^[17] In 1879-1880 the exploration of the highest Andes in South America began when English mountaineer Edward Whymper climbed Chimborazo (20,564 ft (6,268 m)) and explored the mountains of Ecuador.^[18] It took until the late 19th century for European explorers to penetrate Africa. Mount Kilimanjaro in Africa was climbed in 1889 by Austrian mountaineer Ludwig Purtscheller and German geologist Hans Meyer, Mt. Kenya in 1899 by Halford Mackinder.^[19]

The last and greatest mountain range was the Himalayas in Central Asia. They had initially been surveyed by the British Empire for military and strategic reasons. In 1892 Sir William Martin Conway explored the Karakoram Himalayas, and climbed a peak of 23,000 ft (7,000 m). In 1895 Albert F. Mummery died while attempting Nanga Parbat, while in 1899 Douglas Freshfield took an expedition to the snowy regions of Sikkim.^[20]

In 1899, 1903, 1906, and 1908 American mountaineer Mrs. Fanny Bullock Workman (one of the first professional female mountaineers) made ascents in the Himalayas, including one of the Nun Kun peaks (23,300 ft (7,100 m)). A number of Gurkha sepoys were trained as expert mountaineers by Charles Granville Bruce, and a good deal of exploration was accomplished by them.^[20]

In 1902 the Eckenstein-Crowley Expedition, led by English mountaineer Oscar Eckenstein and English occultist Aleister Crowley was the first to attempt to scale K2. They reached 22,000 feet (6,700 m) before turning back due to weather and other mishaps. Undaunted, in 1905 Crowley led the first expedition to Kangchenjunga, the third highest mountain in the world, in an attempt described as "misguided" and "lamentable".^[20]

Eckenstein was also a pioneer in developing new equipment and climbing methods.

He started using shorter ice axes which could be used single-handed, designed the modern crampons and improved on the nail patterns used for the climbing boots.^[21]

By the 1950s, all the eight-thousanders but two had been climbed starting with Annapurna in 1950 by Maurice Herzog and Louis Lachenal on the 1950 French Annapurna expedition. The last great peak was the highest of them all, Mount Everest. The British had made several attempts in the 1920s; the 1922 expedition reached 8,320 metres (27,300 ft) before being aborted on the third summit attempt after an avalanche killed seven porters. The 1924 expedition saw another height record achieved but still failed to reach the summit with confirmation when George Mallory and Andrew Irvine disappeared on the final attempt. The summit was finally reached on May 29, 1953 by Sir Edmund Hillary and Tenzing Norgay from the south side in Nepal.^[20]

Just a few months later, Hermann Buhl made the first ascent of Nanga Parbat (8,125 m), a siege-style expedition culminating in a last 1,300 meters walking alone, being under the influence of drugs: pervitin (based on the stimulant methamphetamine used by soldiers during World War II), padutin and tea from coca leaves. K2 (8,611 m), the second-highest peak in the world, was first scaled in 1954 by Lino Lacedelli and Achille Compagnoni. In 1964, the final eight-thousander to be climbed was Shishapangma (8,013 m), the lowest of all the 8,000 metre peaks.^[20]

Long the domain of the wealthy elite and their agents, the emergence of the middle-class in the 19th and 20th centuries has resulted in mass interest in mountaineering.

It is now a popular pastime of many people.^[5]

Mountaineering techniques vary greatly depending on location, season, and the particular route a mountaineer chooses to climb.

Mountaineers train to climb on all types of terrain whether it be level ground, rock, snow, or ice.

Each type of terrain presents its own hazards.

Mountaineers must possess adequate food, water, information, and equipment to complete their tasks.^[4]

The term "walk-up" is used to describe terrain in which no technical equipment is needed.^[22] To traverse this terrain, mountaineers hike long distances to a base camp or the beginning of rough terrain, either following trails or using navigation techniques to travel cross-country. Hiking may be a strenuous activity, and adequate physical fitness and familiarity with the wilderness is necessary to complete a hike; it is also a prerequisite of success in all aspects of mountaineering.^[4]

Alpine rock climbing involves technical skills including the ability to place traditional protection (cams, nuts, hexes) into the rock to safely ascend a mountain. In some cases, climbers may have to climb multiple pitches of rock in order to reach the top. Typically, for any one pitch, there are belayers who are stationary and create tension on the rope, and climbers who ascend the rock while supported by the rope. The first climber will reach a point on the rock to build an anchor, which will secure subsequent climbers should they take a fall. This anchor could be created by using slings around a tree, a large rock horn or boulder, or by using protection devices like cams and nuts to build an anchor in cracks. Once anchored, the leader will then belay followers, who climb up to their position. Commonly, the leader will then transfer all necessary protection devices (known as a rack) to the follower. The follower then becomes the leader and will ascend the next pitch. This process will continue until the climbers either reach the top, or run into different terrain.^[2][4]

For extremely vertical rocks, or to overcome certain logistical challenges, climbers may use aid climbing techniques. This involves the use of equipment, such as ladders, fixed lines, and ascenders to help the climber push him or herself up the rock.^[2]

In alpine climbing, it is common for climbers to see routes of mixed terrain.

This means climbers may need to move efficiently from climbing glacier, to rock, to ice, back and forth in a number of variations.^[4]

Compacted snow conditions allow mountaineers to progress on foot. Frequently crampons are required to travel efficiently over snow and ice. Crampons attach to a mountaineer's boots to provide additional traction on hard snow and ice. For loose snow, crampons are less suitable, and snowshoes or skis may preferred. Using various techniques from alpine skiing to ascend/descend a mountain is a form of the sport by itself, called ski mountaineering.^[4]

Ascending and descending a snow slope safely requires the use of an ice axe and many different footwork techniques that have been developed over the past century, such as the French technique and German technique. Teams of climbers may choose to attach everyone together with a rope, to form a rope team. The team may then secure themselves by attaching the rope to anchors. These anchors are sometimes unreliable, and include snow stakes or pickets, deadman devices called flukes which are fashioned from aluminium, or objects that might include buried equipment or rocks. Bollards, which are simply carved out of consolidated snow or ice, also sometimes serve as anchors. Alternatively, a roped team may choose not to use anchors; instead all members of the team will prepare to self-arrest in the event should a team member fall.^[4]

It is not always wise for climbers to form a rope team, since one falling climber may pull the entire team off the mountain.

However, the risks of individual, unprotected travel are often so great that groups have no choice but to form a rope team.^[4]

For example, when travelling over glaciers, crevasses pose a grave danger to a climber who is not roped in. These giant cracks in the ice are not always visible as snow can be blown and freeze over the top to make a snowbridge. At times snowbridges can be as thin as a few inches, and may collapse from people walking over them. Should a climber fall, being protected by a rope greatly reduces the risk of injury or death. The other members of the rope team may proceed with a crevasse rescue to pull the fallen climber from the crevasse.^[4]

For extremely slippery or steep snow and ice, climbers must use more advanced techniques, called ice climbing. Specialized tools such as ice screws and ice picks help climbers build anchors and move up the ice. Often, mountaineers climbing ice will not use a fixed belay. Instead each climber on the team will climb at the same time while attached to anchors, in groups of two. This allows for safety should the entire team be taken off their feet. This technique is known as simul-climbing or a running belay and is sometimes also used on steep snow and easy rock. Traditional belays are also used; in this case, this is sometimes necessary due to mixed terrain, steepness, or other factors.^[4]

Climbers use a few different forms of shelter depending on the situation and conditions.

Shelter is a very important aspect of safety for the climber as the weather in the mountains may be very unpredictable.

Tall mountains may require many days of camping on the mountain.^[4]

Short trips lasting less than a day generally do not require shelter, although for safety, most mountaineers will carry an emergency shelter, such a light bivouac sack.^[4]

Typical shelters used for camping on mountaineering terrain include tents and bivouac sacks. The ability of these shelters to provide protection from the elements is dependent on their design. Mountaineers who climb in areas with cold weather or snow and ice will use more heavy-duty shelters than those who climb in more forgiving environments.^[4]

In remote locations, mountaineers will set up a "base camp", which is an area used for staging attempts at nearby summits.

Base camps are positioned to be relatively safe from harsh terrain and weather.

Where the summit cannot be reached from base camp in a single day, a mountain will have additional camps above base camp.

For popular mountains, base camps may be at a fixed location and become famous.

The Everest base camps and Camp Muir are among the most famous base camps.

Camping is not always an option, or may not be suitable if a mountain is close to civilization.

Some regions may legally prohibit primitive camping due to concern for the environment, or due to issues with crowds.

In lieu of camping, mountaineers may choose to stay in mountain huts.

The European alpine regions, in particular, have a large network of huts.

Such huts exist at many different heights, including in the high mountains themselves – in extremely remote areas, more rudimentary shelters may exist.

The mountain huts are of varying size and quality, but each is typically centred on a communal dining room and have dormitories equipped with mattresses, blankets or duvets, and pillows; guests are expected to bring and use their own sleeping bag liners. The facilities are usually rudimentary, but, given their locations, huts offer vital shelter, make routes more widely accessible (by allowing journeys to be broken and reducing the weight of equipment needing to be carried), and offer good value. In Europe, all huts are staffed during the summer (mid-June to mid-September) and some are staffed in the spring (mid-March to mid-May). Elsewhere, huts may also be open in the fall. Huts also may have a part that is always open, but unmanned, a so-called winter hut.^[23]

When open and manned, the huts are generally run by full-time employees, but some are staffed on a voluntary basis by members of alpine clubs.

The manager of the hut, termed a guardian or warden in Europe, will usually also sell refreshments and meals, both to those visiting only for the day and to those staying overnight.

The offering is surprisingly wide, given that most supplies, often including fresh water, must be flown in by helicopter, and may include glucose-based snacks (such as candy bars) on which climbers and walkers wish to stock up, cakes and pastries made at the hut, a variety of hot and cold drinks (including beer and wine), and high carbohydrate dinners in the evenings.

Not all huts offer a catered service, though, and visitors may need to provide for themselves.

Some huts offer facilities for both, enabling visitors wishing to keep costs down to bring their own food and cooking equipment and to cater using the facilities provided.

Booking for overnight stays at huts is deemed obligatory, and in many cases is essential as some popular huts, even with more than 100 bed spaces, may be full during good weather and at weekends.

Once made, the cancellation of a reservation is advised as a matter of courtesy – and, indeed, potentially of safety, as many huts keep a record of where climbers and walkers state they plan to walk to next.

Most huts may be contacted by telephone and most take credit cards as a means of payment.^[23]

In the UK the term "hut" is used for any cottage or cabin used as a base for walkers or climbers.

These are mostly owned by mountaineering clubs for use by members or visiting clubs and generally do not have wardens or permanent staff, but have cooking and washing facilities and heating.

In the Scottish Highlands small simple unmanned shelters without cooking facilities known as "bothies" are maintained to break up cross country long routes and act as base camps to certain mountains.

Where conditions permit, snow caves are another way to shelter high on the mountain. Some climbers do not use tents at high altitudes unless the snow conditions do not allow for snow caving, since snow caves are silent and much warmer than tents. They can be built relatively easily, given sufficient time, using a snow shovel. The temperature of a correctly made snow cave will hover around freezing, which relative to outside temperatures can be very warm. They can be dug anywhere where there is at least four feet of snow. The addition of a good quality bivvy bag and closed cell foam sleeping mat will also increase the warmth of the snow cave. Another shelter that works well is a quinzee, which is excavated from a pile of snow that has been work hardened or sintered (typically by stomping). Igloos are used by some climbers, but are deceptively difficult to build and require specific snow conditions.^[4]

Mountaineers face a variety of hazards.

When climbing amounts, there are two types of hazards, objective and subjective. Objective hazards relate to the environment, and may include inclement weather conditions, dangerous terrain, and poor equipment. Subjective hazards relate to a climber's poor judgement, poor planning, lack of skills, or inadequate conditioning.^[2]

In terms of objective hazards, the dangers mountaineers face include falling rocks, falling ice, snow-avalanches, the climber falling, falls from ice slopes, falls down snow slopes, falls into crevasses, and the dangers from altitude and weather.^[24]

The primary dangers caused by bad weather center on the changes it causes in snow and rock conditions, making movement suddenly much more arduous and hazardous than under normal circumstances.

Whiteouts make it difficult to retrace a route while rain may prevent taking the easiest line only determined as such under dry conditions. In a storm the mountaineer who uses a compass for guidance has a great advantage over a merely empirical observer. In large snow-fields it is, of course, easier to go wrong than on rocks, but intelligence and experience are the best guides in safely navigating objective hazards.

Summer thunderstorms may produce intense lightning.^[24] If a climber happens to be standing on or near the summit, they risk being struck. There are many cases where people have been struck by lightning while climbing mountains. In most mountainous regions, local storms develop by late morning and early afternoon. Many climbers will get an "alpine start", that is, before or by first light, so as to be on the way down when storms are intensifying in activity and lightning and other weather hazards are a distinct threat to safety. High winds can speed the onset of hypothermia, as well as damage equipment such as tents used for shelter.^[24][25] Under certain conditions, storms can also create waterfalls which can slow or stop climbing progress. A notable example is the Föhn wind acting upon the Eiger.

Rapid ascent can lead to altitude sickness.^[24][26] The best treatment is to descend immediately. The climber's motto at high altitude is "climb high, sleep low", referring to the regimen of climbing higher to acclimatise but returning to lower elevation to sleep. In the South American Andes, the chewing of coca leaves has been traditionally used to treat altitude sickness symptoms.

Common symptoms of altitude sickness include severe headache, sleep problems, nausea, lack of appetite, lethargy and body ache.

Mountain sickness may progress to HACE (High Altitude Cerebral Edema) and HAPE (High Altitude Pulmonary Edema), both of which can be fatal within 24 hours.^[24][26][26]

In high mountains, atmospheric pressure is lower and this means that less oxygen is available to breathe.^[24] This is the underlying cause of altitude sickness.

Everyone needs to acclimatise, even exceptional mountaineers that have been to high altitude before.^[28] Generally speaking, mountaineers start using bottled oxygen when they climb above 7,000 m. Exceptional mountaineers have climbed 8000-metre peaks (including Everest) without oxygen, almost always with a carefully planned program of acclimatisation.

There are two main styles of mountaineering: expedition style and alpine style.

Alpine style, or informal variations of it, is the most common form of mountaineering today.

This style is most suited for medium-sized mountain areas (2,000–5,000 m (6,600–16,400 ft)) close to civilization such as the Alps or Rocky Mountains. Alpine style ascents have been done throughout history on extreme altitude (5,000–8,848 m (16,404–29,029 ft)) peaks also, albeit in lower volume to expedition style ascents. Alpine style refers to a particular style of mountain climbing where climbers generally their loads between camps without backtracking, in a single push for the summit. If the summit is reachable from the base camp or trailhead within one day, then alpine-style mountaineers will not change camps at all, and only carry the slightest of loads (necessary nourishment and equipment) up to the summit. "Light and fast" is the mantra of the alpine mountaineer.^[4]

The alpine style contrasts with "expedition style".

Climbing in an expedition style is preferred if the summit is very high or distant from civilization.

Climbers will carry large amounts of equipment, and will usually be a part of a large entourage.

To cover large distances with the massive of amount of gear, expedition mountaineers will often employ porters or use sleds.

Multiple camps are always utilized, and climbers will haul their gear up the mountain multiple times, returning to a lower camp after each haul except for the last; and repeating this procedure until they reach the summit.

This technique is also helpful for acclimatization.^[4] While it is the original style in which high mountains were climbed, expedition style is rare these days as more mountains have become accessible to the general public.

It is still common in ranges such as the Alaska Range and the Himalayas.

The differences between, and advantages and disadvantages of, the two kinds of climbing are as follows:^[4]