The challenges of commercial mountaineering on the highest Volcanic Seven Summit, the Ojos del Salado 23Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.DOI: 10.15201/hungeobull.72.1.2 Hungarian Geographical Bulletin 72 2023 (1) 23–40. Introduction The meaning of mountaineering has evolved significantly during the 20th century; from a form of elite activity – i.e. climbing a moun- tain with as little outside help as possible – to a wide-ranging term encompassing climbing, via-ferrata, backpacking, trekking and hiking in mountainous regions (Apollo, M. 2017). Due to the increasing popularity of outdoor sports and the growing availability of extreme travel destinations, the volume of amateur mountaineering has been increasing stead- ily during the last few decades. As the vast majority amateur mountaineers use commer- cial tour operators, high altitude mountain trekking and climbing represents a strongly emerging new form of tourism (Johnston, B.R. and Edwards, T. 1994; Apollo, M. 2017). Widely known global mountaineering challenges have been playing a key role in the popularisation of professional and semi- professional mountaineering (Hamill, M. 2012; Romero, J. 2014; Buckingham, E. 2015). 1 Department of Physical Geography, ELTE Eötvös Loránd University, Pázmány P. sétány 1/a, H-1117 Budapest, Hungary. 2 School of Geographical Sciences, University of Bristol; Bristol, BS8 1HH, United Kingdom. Corresponding author’s e-mail: a.igneczi@bristol.ac.uk 3 Department of Methodology for Business Analysis, Budapest Business School, University of Applied Sciences; Alkotmány u. 9–14, H-1054 Budapest, Hungary. 4 Escuela de Ingeniería, Pontificia Universidad Católica de Chile; PermaChile Network, Santiago de Chile, Chile. 5 Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary. 6 SOS Hungary Medical Service, Szentendrei út 103, H-1039, Budapest, Hungary. The challenges of commercial mountaineering on the highest Volcanic Seven Summit, the Ojos del Salado Balázs NAGY1, Ádám IGNÉCZI 2, Ilona KOVÁCS-SZÉKELY3, Sebastián RUIZ PEREIRA4, Gábor MIHAJLIK5, Péter FELKAI6 and László MARI1 Abstract Commercial mountaineering has gained widespread popularity in recent decades. Global mountaineering chal- lenges – e.g., the Seven Summits challenge to climb the highest summit of each continent – amplify this process, and also raise the profile of individual destinations. The highest volcano on the Earth, the Ojos del Salado in the Dry Andes (Chile/Argentina) is featured in two of the major challenges (Seven Second Summits, Volcanic Seven Summits). Thus, it is a prime extreme outdoor tourism destination. The relative ease of access and the non-technical nature of the ascent have also contributed to the increasing volume of tourism. However, our observations about commercial mountaineering practices reveal surprisingly low success rates on the summit. Based on data from our decade-long environmental monitoring programme and our field experiences,, we attribute this to the extreme environment and landscape of the mountain (e.g., cold and dry climate, strong winds, topographical situation, loose surface material), scarce mountaineering facilities, and potential misjudgements by inexperienced climbers. Keywords: Ojos del Salado, Andes, outdoor tourism, commercial mountaineering, extreme environment, extreme landscape Received December 2022, accepted March 2023. Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.24 A classic example is the Seven Summits challenge to climb the highest summit of each continent (Table 1, column 2–3), which was proposed in 1988 (Bass, M. et al. 1988; Bell, S. 2000). Newer mountaineering chal- lenges are also emerging, e.g., the Seven Second Summits challenge to climb the second highest point of each continent (see Table 1, column 4–5) (Horrel, M. 2012), and the Volcanic Seven Summits to climb the highest volcanoes on all the continents (Table 1, column 6–7). The latter was pro- posed in 1999 and first completed in 2011 (Andalkar, A. 1999; Cairns, S. 2020; Traver, M. 2020; Rohnfelder, A. 2021; Stone, J. 2022). Although several of these summits are technically, physically, and/or financially de- manding to climb (e.g., Mount Everest, Vinson Massif), others are more accessible for ama- teurs and hiking enthusiasts (e.g., Aconcagua, Kilimanjaro, Puncak Jaya). Hence, while only a few hundred people have completed one of these challenges (Jurgalski, E. and Kikstra, H. 2016), the popularity of accessible and non- technical – i.e. no specialised mountaineering techniques and equipment required – summit challenge locations has skyrocketed due to the achievement and perceived prestige of climb- ing such a peak (Nüsser, M. and Dame, J. 2015). Although this brings economic benefits, there are growing concerns about the increased en- vironmental strain on fragile high-mountain environments (Johnston, B.R. and Edwards, T. 1994; Marek, A. and Wieczorek, M. 2015). The highest peak of the Volcanic Seven Summits – i.e. the highest volcano on the Earth – is the Ojos del Salado (6,893 m a.s.l.) in the Dry Andes on the border of Chile and Argentina. This peak, first climbed in 1937 (Carter, H.A. 1957), is also included in the Second Seven Summits challenge, which makes it a prime target for amateur mountaineers and outdoor enthusiasts. The Ojos del Salado boasts easy access on the Chilean side (used by > 90% of the climbers), moderate altitude com- pared to an 8,000 m high peak (while still being the highest peak in its category), no significant ice coverage (Nagy, B. et al. 2019), no volcanic activity, and no significant danger from falling due to exposed rock faces. Most of the ascent is achieved by trekking up on a footpath criss- crossing a steep scree slope, while only the last 30–40 m involves exposed climbing through a steep couloir and a ridge. However, holds and supports are abundant, and fixed ropes are also available to assist this last part of the ascent. These characteristics usually indicate a relatively easy ascent that is achievable for a wide-variety of prospective climbers, e.g., people without significant mountaineering and outdoor experience (Doran, A. and Pomfret, G. 2019). Due to these factors, the Ojos del Salado gained considerable fame and popular- ity in recent decades and attracts an increasing number of climbers. However, the extreme environment of the mountain (e.g., it is one of the driest region of the Earth) is challenging for a lot of climb- Table 1. Summits included in the different „Seven challenges” Continent Seven Summits Seven Second Summits Volcanic Seven Summits Name Height, m Name Height, m Name Height, m Asia South America North America Africa Europe Europe* Antarctica Australasia Mount Everest Aconcagua Denali Kilimanjaro Elbrus Mont Blanc Vinson Massif Puncak Jaya 8,848 6,962 6,194 5,895 5,642 4,810 4,892 4,884 K2 Ojos del Salado Mount Logan Mount Kenya Dykh-Tau Monte Rosa Mount Tyree Puncak Mandala 8,611 6,893 5,959 5,199 5,205 4,634 4,852 4,760 Damavand Ojos del Salado Pico de Orizaba Kilimanjaro Elbrus Etna Mount Sidley Mount Giluwe 5,671 6,893 5,636 5,895 5,642 3,357 4,282 4,367 *The highest summits for Europe vary among different listings, depending on how the boundary between Europe and Asia is defined. 25Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. ers – many of whom are unexperienced – and contributes to a very low success rate (below ~ 30%) of reaching the summit. This causes concerns about the sustainability of the busi- ness model of private tour operators, and also about the health and safety of climbers, espe- cially if tourist numbers increase any further. Increasing tourism also leads to significant en- vironmental degradation, especially in highly vulnerable extreme environments. Thus, the Ojos del Salado is a prime location to investi- gate the relationship between mountaineering tourism and the vulnerable environment of high-altitude mountains. Furthermore, con- clusions learned on the Ojos del Salado are directly transferable to other high-altitude desert volcanoes in the Dry Andes (e.g., Llullaillaco, Socompa, Bonete, Pissis, Cerro Incahuasi) that are expected to see an in- creased number of visitors in the near future. In this paper, we build on our decade long field experience on the Ojos del Salado (be- tween 2008 and 2022) and the results of our environmental monitoring programme (Nagy, B. et al. 2019) to explore the effects of the ex- treme environment on commercial mountain- eering activities and vice versa. We place a special emphasis on the environmental condi- tions/hazards that hinder successful summit ascents, the potential for environmental deg- radation due to mountaineering tourism, and provide suggestions about good mountaineer- ing practices on the Ojos del Salado. We pro- pose that these issues are relevant to a wide range of stakeholders, including academics (both in the natural and social sciences), poli- cymakers, tour operators and climbers. Geographical background The Dry Andes is about a 1,000 km long section of the Andes, mostly located within Chile, Argentina, and Bolivia. The Ojos del Salado is the highest of several – mostly vol- canic – peaks that rise above 6,000 m a.s.l. from the Puna de Atacama, i.e. a vast, high altitude (~ 4,000 m a.s.l.), and mostly unin- habited plateau in the Dry Andes (Figure 1). The climate of these peaks and their vicin- ity is extremely harsh as they fall within the hyper-arid Andean Arid Diagonal, where precipitation – even at the highest altitudes – remains below 100 mm/year due to oro- graphic and oceanic blocking (Amman, C. et al. 2001; Houston, J. and Hartley, A.J. 2003). Furthermore, the spatiotemporal dis- tribution of the precipitation is highly sporad- ic and any snowpack sublimates in a matter of weeks – at the most – in the dry and windy environment (Vuille, M. and Ammann, C. 1997; Vuille, M. 1999). Hence, the climatic snowline is at an extremely high altitude of ~ 7,000 m a.s.l. – the highest on Earth – just above the tallest summits (Clapperton, C.M. 1994; Kull, C. et al. 2002; Grosjean, M. et al. 2007), which prevents the formation of gla- ciers and perennial ice coverage. However, some ice can be found underground in the permafrost (i.e. ground with temperatures below 0 °C for at least two continuous years) above 5,000–5,500 m a.s.l. (Gruber, S. 2012; Gjorup, D.F. et al. 2019; Nagy, B. et al. 2019, 2020). During summer months, the melting permafrost feeds a few small transient ponds above 6,000 m a.s.l. on the Ojos del Salado (Aszalós, J.M. et al. 2020a, b). Due to these extreme conditions, the region has been used as a Mars analog site by several studies (e.g., de Silva, S.L. et al. 2010, 2013; Favaro, E.A. et al. 2020; Kereszturi, Á. et al. 2020, 2022). Historical overview of mountaineering on the Ojos del Salado Based on historical information, and our own experiences since 2008, we delineate 4 stages (periods) of mountaineering and mountain- eering tourism on the Ojos del Salado: Period I. After the first expeditions in the mid-20th century, the 1980s and 1990s were characterised by low volume occasional uncommercialised mountaineering endeav- ours. In April, 1984 a helicopter of the Anglo- American Mining Co. of South Africa crashed on the mountain during a mining survey. As part of the salvage operations, bulldozers Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.26 Fig 1. The Ojos del Salado, viewed from the Puna de Atacama plateau (February, 2016). Our climate monitor- ing sites, the normal mountaineering route, and the locations of several vehicular world records are indicated. The map inset shows the main camps (triangle) and the sites of included in our environmental monitoring program (cross). The nearest human settlement is ~ 150 kms away. 27Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. were used to create a dirt road – reaching 5,900 m a.s.l. – which was used to transport heavy equipment and a double container (Refugio Tejos/Tejos Camp at 5,830 m a.s.l.) serving as a base of operations (Photo 1). This access route is still in use today. Period II. In 2004, the Aventurismo tour operator company got concession from the Chilean government for the Chilean side of the Ojos del Salado. The company was respon- sible for the development and maintenance of three camp sites located along the approach to the Ojos del Salado: Camp Laguna Verde (4,350 m a.s.l.), Camp Atacama (5,260 m a.s.l.), Camp Tejos (5,830 m a.s.l.) (see Photo 1). They provided communal dome tents, field radios, waste collection, and a mountain rescue ser- vice equipped with portable hyperbaric bags and oxygen canisters. These safety and com- fort facilities contributed to the increasing vol- ume of tourism on the Ojos del Salado, which was designated as a zone of special environ- mental/touristic interest (ZOIT: Zonas de Interés Turístico) in 2006 (Servicio Nacional de Turismo, 2006). The annual number of climb- ers were around 300–500 during this period. Period III. After the Aventurismo conces- sion ended in 2015, all the aforementioned Photo 1. Mountaineering camps on the Chilean side of the Ojos del Salado. a = Tejos Camp at 5,830 m a.s.l. in February, 2020; b = Atacama Camp at 5,260 m a.s.l. in March, 2018; c = Laguna Verde Base Camp at 4,350 m a.s.l. in January, 2010, dome tents provided by Aventurismo during the concession period (between 2004 and 2015) are visible. Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.28 services and facilities on the mountain were discontinued. Hence, since 2015 the Ojos del Salado is an independent mountaineering destination, i.e. it is possible to access and climb the summit independently and with- out any compulsory fees. However, the lack of infrastructure also hinders independent commercial operators. During this period, which lasted about 3–4 years, visitor numbers stagnated at about 400–500 person per year. Period IV. In 2018, paving the National Highway 31 between Chile and Argentina was completed. This road provides direct and quick access to the Laguna Verde Camp. Meanwhile, most facilities on the mountain – except organised mountain rescue – were re-established by independent tour opera- tors. The majority of tour groups started us- ing 4WD vehicles to ferry equipment and supplies (and sometimes climbers) up the Tejos Camp at 5,830 m a.s.l. Tourism became highly concentrated in time, about 90 per- cent of the 500–600 annual visitors (pre-covid terminus) come in January and February. This is causing environmental strain – e.g., the quick degradation of the campsites – and raising the risk of accidents (Marek, A. and Wieczorek, M. 2015). Meanwhile, there is still no enhanced environmental protec- tion from the government, e.g., the nearby Nevado Tres Cruces National Park (estab- lished in 1994) does not cover the area. Methods Within the framework of our climate- and en- vironmental monitoring programme which started in 2008 (http://permachile.com), we have gathered a significant amount of quantitative data about the environmental conditions – such as temperature, aridity, wind – that can affect and potentially limit commercial mountaineering activities in the region. Our data collection strategy focuses on the monitoring of permafrost and ground ice in every major environmental zone of the region. Thus, measuring ground temperature and humidity, using data loggers (HOBO Pro v2; operation range: −40 °C to 70 °C, accuracy: ±0.21 °C), is our key activity on the field (Nagy, B. et al. 2019). Our loggers are buried at different depths (10–60 cm) and at several locations between the elevations of 4,550 and 6,893 m a.s.l. (see Figure 1). The same data log- gers are also used to record air temperature and humidity at two locations, near the Tejos Camp (though at the slightly higher elevation of 6,000 m a.s.l.), and on the Ojos del Salado summit (see Figure 1). To investigate wind speed and its capacity to transport sediment, we installed sediment-traps at 5,200 m and 6,000 m a.s.l. – near the Atacama and Tejos Camps respectively (see Figure 1). We also installed and operated a mobile meteorolog- ical station while staying at the Tejos Camp between 11–14, February, 2016, to measure radiation and energy balance, wind speed and direction, air temperature, air humidity, and dew formation. Besides, in-situ measurements and sampling, we also utilise satellite imagery – Landsat 7 ETM+, Landsat 8 OLI, and MO- DIS (Moderate Resolution Spectro-radiome- ter) – to survey the sporadic snow coverage (Nagy, B. et al. 2019). Since 2008, our team – collectively – spent 10 summer climbing seasons (in 2008, 2010, 2012, 2014, 2016, 2018, 2019, 2020, 2022, 2023) on the Ojos del Salado, reaching the summit 9 times. A key difference between our pres- ence and the activities of commercial tours is that we spend around 4 weeks – of which about 2 weeks is in the highest regions (i.e. above 5,800 m a.s.l.) – on the mountain con- tinuously, whereas commercial tours typical- ly spend about 1 week on the Ojos del Salado. This has provided us ample opportunity to interact with several commercial tours per climbing season and observe their activities. Hence, besides our numerical data, we can also rely on our extensive field experience on the mountain to evaluate – within the con- text of our environmental data – the common practices and mountaineering strategies of commercial tour operators. We also use offi- cial records from the Chilean Border Agency (DIFROL: Dirección Nacional de Fronteras y Límites del Estado) and the Chilean Tourism http://permachile.com 29Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. Agency (SERNATUR: Servicio Nacional de Turismo) to assess tourism volumes (Servicio Nacional de Turismo, 2014) and success rates. However, there are several shortcom- ings of these data sources: (1) no official permits are required to climb the Ojos del Salado, foreigners need to obtain DIFROL permits but these are not related to climbing; (2) Aventurismo and other private operators do not maintain reliable public records about successful and unsuccessful attempts on the summit due to conflict of interest. Challenging environmental conditions on the Ojos del Salado As environmental conditions are substantial in determining the success on high altitude summits, climbers are in need of detailed information about the typical conditions on a mountain (e.g., snow coverage, water resources, typical temperature range etc.) and short-term predications (e.g., mete- orological forecasts). Below we list and de- scribe the most important and challenging environmental factors on the Ojos del Salado based on data obtained by our environmen- tal monitoring programme. We also evalu- ate how these conditions affect the typical mountaineering strategies and activities of commercial tours – that we observed during our decade long presence on the mountain – with a special emphasis on providing best practice guidance. Topographical situation and high altitude Low oxygenation which might lead to acute mountain sickness (AMS), is the principal consequence of high altitudes on human physiology. This is caused by lower oxygen concentration at high altitudes due to lower air pressure. Respiratory humidification – i.e. attaining saturation water pressure in the air- ways and lungs – also has a proportionally greater effect in oxygenation at high altitude (Brown, J. and Grocott, M. 2013). In order to manage the problem of low oxygenation and to avoid AMS, a well-planned acclimatisation strategy is essential. However, preparing and executing this strategy is a major challenge on the Ojos del Salado due to the topographical situation of the summit and the wider region. Successful acclimatisation requires a “climb high, sleep low” approach. However, the possibility of gradual ascent – i.e. no large jumps in sleep height but a large enough differences between sleep and climb heights – is limited on the Ojos del Salado as it towers ~ 2,500 m above the surrounding Puna de Atacama, a vast rocky desert plateau at around 4,000 m a.s.l. (see Figure 1). It is quite typical to start acclimatization ascends from the Puna de Atacama, thus, mountain- eers spend most of their time (> 90%) above 4,000 m a.s.l. while climbing the Ojos del Salado. The medevac of AMS patients is also hindered by the large distances (> 100 km) on the high-altitude (> 4,000 m a.s.l.) plateau, though newly paved roads largely alleviate this problem. Settlements where medical help is available are even further, around 250 km from the mountain. These factors are compounded by the lack of organised mountain rescue services, which means that oxygen bottles and portable hyperbaric bags (Gamov bags) are not readily available on the mountain, and medevac needs to be or- ganised ad hoc. The possibility of a vehicu- lar ascent to 5,900 m a.s.l. is also tempting – especially for inexperienced tourists – and could lead to quick onset AMS cases. Cold temperatures As the Tejos Camp (5,830 m a.s.l.) is the main staging area for summit attempts, it is important to know typical temperatures in the vicinity of this site. The annual mean air temperature is -10.03 °C at 6,000 m a.s.l., based on our measurements between 2014 and 2020. Although a linear trend fitted on monthly mean temperatures between March, 2014, and March, 2020, reveals a warming of +2.42 °C (Figure 2), summer climbing season Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.30 (Dec-March inclusive) temperatures remained largely unchanged. Hence, we propose that the -6.22 °C mean climbing season (Dec- March) temperature is fairly representative for the Tejos Camp (see Figure 2). As summit- ing and returning takes about 10–15 hours from the Tejos Camp (5,830 m a.s.l.), starting before dawn, it is important to know the typ- ical daily variability of temperatures. Although the highest daily maximum temperatures (~ 19 °C) were observed in December, the overall daily temperature variability is more suitable for climbing in January (Figure 3). This is due to warmer minimum and average temperatures which are especially pronounced during the cru- cial early hours before dawn. On a typical January day, these early morning tempera- tures hold between -5 °C and -7 °C, while in December they consistently hover around -10 °C (see Figure 3). February is similarly suitable though slightly colder (by around 1 °C), while March is distinctively more cold in all regards, and, thus, less suitable for climbing. In fact, typical afternoon tem- peratures in March dip well below December temperatures (see Figure 3). Our measurement site at 6,750 m a.s.l. is sit- uated immediately above a steep 700 m high scree slope – the bulk of the elevation gain during climbing. This site is usually reached by climbers before noon. From here, climb- ers only need to ascend a further 150 m to the summit, though this ascent is on a steep rock wall – the most technically challenging part of the climb. This impressive and intimidat- ing cliff is visible from this site, and many climbers give up at this point due to exhaus- tion and self-doubt (Nüsser, M. and Dame, J. 2015). The exposed and windy conditions at this location also contribute to the deterrence, thus, it is important to know the typical condi- tions here. Although our loggers are buried at 10 cm depth, we argue that they represent air temperatures well as the regolith is extremely coarse, porous, dry, and well ventilated (Nagy, B. et al. 2019). The annual mean (ground) tem- perature at this location during the 2012–2020 period is -14.86 °C. During midday, when most climbers reach the site, temperatures are at around -10 °C (see Figure 3). Similar to the Tejos Camp, January and February are the most favourable months for climbing, due to the mildest typical minimum temperatures (see Figure 3). The last 30–40 m climb to the Ojos del Salado summit leads through a steep couloir, an exposed windy ridge, and crumbly bed- rock. As the progress of climbers is slow and queueing might occur, especially with larg- er groups, timing the arrival well is crucial. Temperatures are generally favourable for Fig. 2. Monthly mean temperatures at 6,000 m a.s.l. near the Tejos Camp between 2014 and 2020. A linear trend, showing the general warming, is also plotted. 31Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. an early afternoon summitting (see Figure 3), which also avoids descending in harsh condi- tions. Similar to lower sites, January provides the best overall conditions, with minimum and mean temperatures between -10 °C and -5 °C (see Figure 3). However, these tempera- tures drop quickly on either side of January, with early afternoon minimums between -20 °C and -15 °C in December and February. Temperatures are even more harsh during the late climbing season in March, when early af- ternoon minimum temperatures are between -20 °C and -25 °C (see Figure 3). Strong winds and wind chill Although, long-term wind speed measure- ments are not available from Ojos del Salado, Milana, J.P. (2009) presented limited data from the Valedero Gold Mine (2000–2002), a comparable site on the Argentinian Puna de Atacama, though ~ 250 km to the south and ~ 3,000 m lower. These measurements indi- cate that wind-speeds between 50–100 km/h occur frequently, while wind-gusts between 250–440 km/h are also possible (Milana, J.P. 2009). As the climate is extremely arid, strong winds move and redistribute sediments easily. Hence, aeolian (wind formed) landforms such as sand dunes, ripple-marks, mega-ripples (Milana, J.P. 2009; Nagy, B. et al. 2019), and bedrock wind abrasion (Photo 2) are abundant in the region. Our sediment traps at 6,000 m a.s.l. also confirm strong wind action, as grains larger than 5 mm – significantly coarser than the sand fraction (0.05–2.00 mm) – were found in the sediment trap 50 cm above the surface. Strong wind can endanger climbers at the ex- posed final approach, thus, it is recommended to monitor wind levels continuously during summit ascents. The presence of coarse wind- blown debris – with grain sizes that can sur- pass that of the sand fraction – is also a key problem (see Photo 2). For example, it can lead to injuries of the cornea, thus, using protective glacier/ski googles is highly recommended. Abundant wind-blown sediment also signifi- cantly deteriorates the camping experience (e.g., sand filling tents and sleeping bags, and contaminating meals), which contributes to the exhaustion of climbers. Fig. 3. The mean (solid line), minimum (transparent dashed line), and maximum (transparent dotted line) hourly temperatures measured between 2014 and 2020 near the Tejos Camp 6,000 m a.s.l (left); between 2012 and 2020 at the Crater Edge 6,750 m a.s.l. (middle); and between 2014 and 2015 at Ojos del Salado summit 6,893 m a.s.l. (right). Months of the climbing season (Dec, Jan, Feb, Mar) are calculated and plotted separately using different colours (see legend). Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.32 However, the most important consequence of strong wind is its negative effect on apparent temperature, as moving air leads to more inten- sive/quick body heat loss, i.e. wind chill (Eq. 1). Twc = 13.12 + 0.6215 · T – 11.37 · v0.16 + 0.3965 · T · v0.16, (Eq. 1) where Twc is wind chill equivalent tempera- ture (°C), T is air temperature (°C), and v is wind velocity (km/h). Wind chill is especially problematic during summit attempts due to the combination of early morning low temperatures and high winds. Even a very mild 10–20 km/h wind – which is almost constant in the region – can lead to wind chill equivalent temperatures (ap- parent temperatures) of -10 °C and -15 °C at the Tejos Camp during a typical January morn- ing (Figure 4). This can easily become 5–10 °C colder on either side of January or simply due to stronger winds. Wind chill might also negate warming which occurs later in the afternoon (see Figure 4), as winds generally pick up speed in parallel with the warming. It is notable, that even though temperatures appear suitable late in the climbing season (e.g., March) wind chill might cause apparent temperatures around -30 °C on the summit (see Figure 4) making frostbite of the extremities a distinct possibil- ity. This illustrates the problems with winter climbing, when daily mean temperatures on the summit are at around -25 °C while appar- ent temperatures can dip below -40 °C. Low precipitation and humidity There are no in-situ precipitation measure- ments from the highest regions of the Puna de Atacama, but numerical estimations yield very Photo 2. Aeolian processes on the slopes of the Ojos del Salado. a-b = Megaripples near the Atacama Camp at 5,250–5,300 m a.s.l. (February, 2020); c-d = wind-abrasion of a boulder (c: windward side, d: leeward side) at 5,900 m a.s.l. (February, 2012); e/1-2 = sandstorm on the lower slope of the Ojos del Salado at 5,300 m a.s.l. (February, 2010). 33Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. low values that are consistent with a desert en- vironment even at high elevations (Amman, C. et al. 2001). Thus, this area can be considered the highest desert on Earth, where precipitation and snow coverage is extremely sporadic and low. However, strong individual precipitation events can occur due to special synoptic metro- logical circumstances (Wilcox, C.A. et al. 2016), e.g., April, 2015 and February, 2018 (Figure 5). Sudden, local snow storms can also occur al- most any time, though they rarely cover the whole mountain. These snow storms mostly arrive from the east and they can be electrically charged, e.g., our loggers on the summit were burned by a lightning storm in 2013. The low precipitation and strong sublima- tion – due to the dry air, high wind, and strong insolation – strongly limit the persistence of snow on the ground. Thus, during the sum- mer climbing season, the mountain is mostly snow free at around 5,000 m a.s.l., and even at around 6,000 m a.s.l. snow usually only persists for a few weeks (see Figure 5). This scarcity of reliable local freshwater supply force climbers to transport their whole stock of drinking water from Copiapó, 250 km away. Despite the lack of a spatially and temporally consistent snowpack on the mountain, local sheltered snow patches occur, especially near the crater rim where they are present in most years (see Figure 5). If the snow cover/patch is fresh and thick, it represents a significant obstacle for climbers, though sublimation can quickly diminish this. Refrozen snow patch- es are fairly easy to traverse by crampons, though it is important to do this well before midday before any significant melting. The aforementioned sudden precipitation events (synoptic or local) can also unexpectedly dis- rupt the climbing process, as most climbers only plan to spend a few days at the Tejos Camp. Furthermore, climbers are usually un- prepared to deal with snowy/icy conditions in this extremely arid environment. Thus, a large proportion of climbers turn back from around 6,300–6,500 m a.s.l. in snowy conditions. Low precipitation, the scarcity of sur face snow, ice, liquid water, and strong winds all Fig. 4. Typical daily temperatures during the climbing season – i.e. mean of the hourly temperatures – and the corresponding wind chill equivalent temperatures at 10 km/h (transparent dotted line) and 50 km/h (transpar- ent dashed line) wind speeds near the Tejos Camp 6,000 m a.s.l. (between 2014 and 2020) (left); and at the Ojos del Salado summit 6,893 m a.s.l. (between 2014 and 2015) (right). Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.34 contribute to the extremely low water vapor content of the air (i.e. humidity). According to our measurements, the absolute (i.e. volu- metric) air humidity (AH) – mass of water vapor divided by the volume of the air and water vapor mixture – near the Tejos Camp (at 6,000 m a.s.l.) is ranging between 0.5 and 1.5 g/m3 during a typical climbing sea- son morning (Figure 6). This is only about 5–15 percent of the optimal range of 9–13 g/m3, i.e. 40–60 percent relative humid- ity at room temperature (Sterling, E.M. et al. 1985; Vellei, M. et al. 2017). Extremely dry air is even more pronounced on the Ojos del Salado summit, where the typi- cal daily maximum AH is only about 1 g/m3, ~ 8–11 percent of the normal range. Early afternoon – the typical time of sum- mitting – AH is even lower at around 0.5 g/m3, ~ 4–6 percent of the normal range (see Figure 6). Extremely low humidity is a major health concern for climbers (Davies, E.D. et al. 2016; Ladd, E. et al. 2016) as – com- pounded by the high rate of respiration – it leads to the severe drying of the skin around the mouth and nose and the mucosal lin- ing of the airways (Tsutsumi, H. et al. 2007; Takada, S. and Matsushita, T. 2013). The dry Fig. 5. Snow cover (light blue: partial snow coverage; dark blue: full snow coverage) at the Atacama Camp (5,260 m a.s.l.), Tejos Camp (5,830 m a.s.l.), and Crater Edge (6,750 m a.s.l.). Data is derived from Landsat and MODIS (aboard both Aqua, and Terra satellites) imagery for 2012–2020. Grey highlights represent the climbing seasons. 35Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. mucosa of the larynx could produce a dry, hacking cough named high altitude bronchi- tis (Cogo, A. et al. 2004; Ladd, E. et al. 2016), and skin dryness could also lead to injuries of the epidermis. High insolation The sky is usually clear until early afternoon in the climbing season, with mild overcast conditions typically prevailing later in the day. Although our records are short – just 3 complete days in February, 2016 – they in- dicate extremely high solar irradiation with hourly averages at around 1,100 W/m2, even during overcast conditions (Figure 7). We pro- pose that this is due to the combination of high altitude and extremely low humidity which cause very low scattering of the incoming solar radiation (global radiation). Individual instances of higher insolation than 1,370 W/m2 – i.e. solar irradiation at the top of the atmos- phere – were also measured occasionally. We propose this is caused by reflection from high level clouds (Breuer, H. et al. 2020). Dry, crumbly and unstable debris cover Most of the Ojos del Salado mountain is cov- ered by an unsorted (i.e. containing various grain sizes mixed together) mantle of debris/ regolith, predominantly containing sand, pum- ice, and pyroclastic debris (Photo 3). Although permafrost is present above 5,600–5,800 m a.s.l. on the Ojos del Salado, ice that could ce- ment the regolith is almost completely absent from the upper layers of the debris mantle during the summer climbing season (Nagy, B. et al. 2019). This is due to the low overall water content of the regolith – caused by the combi- nation of arid climate and high porosity – and the presence of a 20–70 cm active layer (i.e. zone with temperatures above 0 °C underlain by permafrost) during the summer (Nagy, B. Fig. 6. The mean (solid line), minimum (transparent dashed line), and maximum (transparent dotted line) of the hourly absolute air humidity (g/m3) measured between 2014 and 2020 near the Tejos Camp 6,000 m a.s.l (left); and between 2014 and 2015 at Ojos del Salado summit 6,893 m a.s.l. (right). Months of the climbing season (Dec, Jan, Feb, Mar) are calculated and plotted separately using different colours (see legend). Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.36 et al. 2019, 2020). Hence, the surface is extreme- ly loose/unconsolidated which makes walk- ing/climbing difficult and exhausting due to repeated slipping. The unconsolidated surface material also intensifies the strong aeolian action in the vi- cinity of the Ojos del Salado (see section Strong winds and wind chill). This leads to the forma- tion of thick sand layers or small sand dunes at around 5,000–5,800 m a.s.l., which are difficult to traverse (see Photo 3). The removal and re- distribution of finer sediments can also leave behind coarse grained lag gravel pavements. Although these areas appear stable, usually the underlying fine sediments cannot support the weight of an adult, thus, walking across these is challenging as well (see Photo 3, a). A summary of key challenges during different climbing stages Conquering the Ojos del Salado is a fairly mo- notonous experience for most, as climbers usu- Photo 3. High mountain desert-surface of the Ojos del Salado, a = coarse lag gravel pavement at 5,650 m a.s.l. (February, 2010); b = eolian sand-blanket at 5,840 m a.s.l. (February, 2016); c = sandy debris slope near the Camp Atacama at 5,350 m a.s.l. (January, 2012). Fig. 7. Incoming solar radiation at the Tejos Camp (5,830 m a.s.l.) during 3 days in February, 2016. The solid line represents the average incoming radiation, while the shaded area represents the minimum-maximum range for each 30 minute measurement period. 37Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40. ally spend more than a week in the close vicin- ity, which is a barren rocky desert. This physi- cally and mentally draining experience is ex- acerbated by the unique combination of harsh environmental conditions. The topographical situation of the Ojos del Salado also hinders the planning and execution of a successful ac- climatisation strategy. The high altitude, strong irradiation, dry air, strong winds all contribute to the severe dehydration and strong coughing that afflicts most climbers. Furthermore, even though actual air temperatures are not particu- larly low in the climbing season, strong wind chill could lead to frostbites. Unstable and slow walking on to the highly porous, dry and crum- bly debris cover is a continuous problem which contributes significantly to the exhaustion of climbers. This debris covers and the strong winds also make camping a challenging, un- comfortable which hinders the relaxation and recovery of climbers. In fact, several geographi- cal names in the region indicate physical hard- ship, isolation, hopelessness (e.g., Cerro Mulas Muertas – Peak of the Dead Mules; Cerro El Muerto – Dead Peak, etc.) which might reflect the challenges early explorers faced. The most physically and mentally challenging – though technically easy – part of climbing the Ojos del Salado is trekking up the exposed, steep scree slope between Tejos Camp and the crater rim (6,000 to 6,750 m a.s.l.). Although this sec- tion of the climb just requires following the zig- zagging footpath up the slope, resting places are scarce and the surface debris is very unstable. Thus, climbers often slide one or two steps down which is exhausting and frustrating. A large pro- portion of the climbers give up the attempt on the summit in the middle of this slope, at around 6,300–6,400 m a.s.l. A fairly consistent snow/firn patch also intersects the footpath to the sum- mit at around 6,500 m a.s.l. that usually poses a significant challenge for climbers. In most cases, crampons are needed here – especially during the early hours – which are challenging to equip on the steep scree slope. At the top of the scree slope, on the crater edge, the largest challenge is mostly psycholog- ical.Climbers catch their first up-close glimpse of the Ojos del Salado summit from this loca- tion. The steep rocky peak about 150 m above the crater rim, looks intimidating for the inex- perienced. This, combined with the exhaustion due to the long climb on the scree slope and the unpleasant cold and windy early morning weather nudges many to turn back. Also, the bright orange container at the Tejos Camp is well visible from here, which tempts many to retreat to its comparable comfort. Scaling the actual peak from the crater rim, especially the last 30–40 m, is technically the most difficult part of the climb. However, turn- ing back is not common at this point as the sum- mit is very close. A special source of danger on the Ojos del Salado is the long and tiring de- scent down the scree slope, which usually hap- pens late in the afternoon. Climbers are the most exhausted at this stage and usually have lower coordination of their movements. This, on the unstable surface can lead to injuries and many unscheduled resting stops, partly due to frus- tration. Exhausted climbers who might descent on their own could – and sometimes do – fall asleep during these rest stops, which is danger- ous as temperatures drop quickly at sunset. Conclusions The Ojos del Salado became a popular high altitude mountaineering destination in re- cent years, though the success rate of summit attempts is low. Although mountaineering infrastructure is quite sparse in the region, vehicular approach is easy due to recent road upgrades. Thus, we propose that the most important factor that hinders climbers in reaching the summit – and causing low success rate – is the harsh environment of the region, and the lack of proper considera- tion of these conditions. High altitude, cold temperatures, and strong winds are common environmental conditions on all major peaks. However, on the Ojos del Salado, these are exacerbated by extreme aridity, monotone desert landscape, and unstable surface ma- terial, which strongly accentuate other en- vironmental challenges associated with the high altitude. Nagy, B. et al. Hungarian Geographical Bulletin 72 (2023) (1) 23–40.38 Ensuring gradual acclimatisation on the Ojos del Salado is paramount. Although it is relatively easy to reach high altitudes – e.g., the Atacama Camp (5,260 m a.s.l.) or even the Tejos Camp (5,830 m a.s.l.) – by a 4WD car, climbers should start acclimatisation well before they reach the Atacama Camp, and should continue the process even after that point. However, since the mid-2000s demand for quick and easy access to the mountain has increased. Thus, in a lot of cases, moun- taineering equipment and supplies (drink- ing water, rations, etc.) are transported by car to the Tejos Camp, and a few days later the climbers are also ferried up. Summit at- tempts start from there, and climbers usually descend back to the Atacama Camp. An even more extreme form of this, is using cars to get to the Tejos Camp during the night, summit during the day, and then return to lower al- titudes (even as low as sea-level) as quickly as possible. We propose that the best strategy to safely – but also “cleanly” – climb the Ojos del Salado, is utilising vehicular transport to a limited degree. In this case climbers should spend several nights on the Puna da Atacama, and complete acclimatisation hikes there. Then, they can be transported up to the Atacama Camp by cars, but they should not utilise cars to reach higher altitudes. Cars can also be used to transport supplies and a limited amount of equipment to the Atacama and Tejos Camps. However, using cars have several consequences, beyond tarnishing the achievement of reaching the summit. Chief among these is the environmental degrada- tion, e.g., erosion and noise pollution, and also the larger amount of waste production due to easier transportation. Unfortunately, independent waste collection and removal is still not organised around on the Ojos del Salado. 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