| Llullaillaco | |
|---|---|
.jpg) Llullaillaco from the east | |
| Highest point | |
| Elevation | 6,723 m (22,057 ft) |
| Prominence | 2,344 m (7,690 ft) |
| Listing | Ultra |
| Coordinates | 24°43′11″S68°32′12″W / 24.71972°S 68.53667°W /-24.71972; -68.53667[1] |
| Geography | |
  Llullaillaco Location in Chile (on border with Argentina) | |
| Location | Chile and Argentina |
| Parent range | Andes,Puna de Atacama |
| Geology | |
| Rock age | Pleistocene |
| Mountain type | Stratovolcano |
| Last eruption | May 1877[2] |
| Climbing | |
| First ascent | ByInca, in or before 1520 |
Llullaillaco (Spanish:[ʎuʎajˈʎako],Latin American Spanish:[ɟʝuʝajˈʝako]) is adormantstratovolcano on the border between Argentina (Salta Province) and Chile (Antofagasta Region). It is part of theLlullaillaco National Park and lies in thePuna de Atacama, a region of tall volcanic peaks on a highplateau close to theAtacama Desert, one of the driest places in the world. Its maximum elevation is most commonly given as 6,723 metres (22,057 ft), making it thesecond-highest active volcano in the world. Despite its height, it is not clear whether the volcano has anyglaciers or merely patches of perennial snow and ice. Between3,700 m and5,000 m elevation there is a sparse plant cover, while at lower altitudes the climate is too dry for plants to grow. Aspecies of mouse on Llullaillaco is the vertebrate species living at the highest-known altitude.
The volcano formed during thePleistocene in two stages, named Llullaillaco I and Llullaillaco II. The oldest rocks are about 1.5 million years old. About 150,000 years ago, the volcano's southeastern flank collapsed, generating adebris avalanche that reached as far as 25 kilometres (16 mi) from the summit. During the last stage, three conspicuouslava flows were emplaced on the summit. The youngest-dated rocks are 930 ± 140 years old, but there are reports of activity from the 19th century.
There are archaeological sites on the mountain and at its foot; Llullaillaco marks the highest archaeological site in the world. The first recorded ascent was in 1950. In 1999, themummified remains of three children, known as theChildren of Llullaillaco, were found at its summit. They are presumed to have beenhuman sacrifices.
The nameLlullaillaco is usually associated to theQuechua wordllulla meaning "false", "lie" or "deceitful" andyaku orllaco meaning "water".[3] This name probably refers tomeltwater from snow, which flows down the slopes but then is absorbed into the soil;[4][5] normally mountains are sources for water.[3][6] Another possibility is that it refers to the danger from floods in the local valleys.[7] Other translations are (Aymara) "hot water"[8] afterlloclla "warm" andyacu "water",[9] and (Quechua) "thinking", "memory"+"water"[10] or "thing that hardens after forming tender"llullu, which may refer to volcanic activity.[6]
Llullaillaco is located in the northwestern ArgentineAndes,[11] towards the southern end of thePuna.[12] The frontier between Argentina and Chile passes over the mountain.[13] The Argentine portion is in theLos Andes Department ofSalta Province[14] and the Chilean in Chile'sAntofagasta Region.[15][16] About30 km northeast of Llullaillaco, theSalta–Antofagasta railway crosses the Andes atSocompa.[17] Humans first moved into the area about 8,000BCE.[6] The region was inhabited by hunters and shepherds inpre-Hispanic times.[9] At some point between 1470 and 1532CE, theInca empire occupied the region.[6]
There are numerous abandoned mines in the region,[18] and the activelithium production plant "Proyecto Mariana" at theSalar de Llullaillaco.[19][20] Azufrera Esperanto is an abandoned sulfur mine north of Llullaillaco and is associated with an area of hydrothermal alteration. The mine can be reached through a road or path from the northwest.[21][22] Another abandoned mine lies south of the volcano.[22] Mina Amalia is an abandonedborate mine and Mina Luisa and Mina Maria abandonedsalt mines at Salar de Llullaillaco.[22] Aweather station installed on Llullaillaco in 2004 was for some time the highest in the world.[23] The region is dry and located at high altitudes, making work in the area difficult.[24] The extreme environmental conditions have been compared to conditions onMars.[25]
The volcano is an imposing mountain, rising by3,800 m and3,750 m above theSalar de Punta Negra and theSalar de Llullaillaco,36 km and20 km away, respectively.[24][26] With a summit height of6,723 m,[1][27][28] (or6,739 m[2]) it is one of the highest mountains in the Andes[14] (third highest in Chile[7] and seventh highest in the Andes, according to John Biggar[29]) and the second-[1] or third-highest volcano in the world[13] (Ojos del Salado is the highest[27]). In the early 20th century, Llullaillaco was thought to be the highest volcano in the world.[30] The elevation is to a large degree consequence of the underlying terrain, which rises about4 km above sea level.[31] The height of the mountain and the clear air in the region make Llullaillaco visible fromCerro Paranal,190 km away as measured throughGoogle Earth.[32] The view from the mountain extends fromLicancabur north over theNevados de Cachi mountains east to[6] Ojos del Salado250 km south;[33] mountains in between are visible as well.[6]
Llullaillaco is acomposite volcano formed mostly bylava flows.[13] It rises about2.2–2.5 km above the surrounding terrain[13][27] and hundreds of metres above surrounding mountains.[14] The summit of Llullaillaco is formed by a small cone with about four associatedlava domes,[34] which reach lengths of1–3 km and have abrupt walls.[35] Three hollows, probablyvolcanic craters, lie east of a 200-metre-long crest at the summit.[36] The slopes of the volcano are fairly steep, with an altitude drop of1,800 m over only3 km horizontal distance.[24][26] The slopes high up are steeper than those at lower altitudes.[37] A plateau at5,600–6,100 m elevation is the remnant of an erodedcrater[38] from an early stage in Llullaillaco's development.[39]
Three young-looking,4.5–8 km long lava flows emanate from the summit cone[34] to the north and south.[18] Morphologically, these flows are reddish-blackaa lava flows and feature black and reddish glassy blocks with sizes of5 m.[34][40] The fronts of the stubby, lobe-shaped flows[40] are up to15 m thick.[34] The northern flow has prominentlevee-like structures[41] and splits into a northwestern and northeastern branch[18] upon reaching an obstacle.[42] The southwestern[18] lava flow is6 km long and was fairly viscous when it was erupted.[40] It almost reaches a road southwest of the volcano.[43] The third flow is just east from the southwestern[18] and descends an altitude of2 km.[40] The flows have levee-like structures and ridges.[2] On the northern flank is Azufrera Esperanto, a 5,561-metre-high eroded volcano withsulfur deposits and traces ofhydrothermal alteration.[34] The existence of a cave on Llullaillaco is doubtful.[44] The edifice covers an elliptical area of23 km × 17 km[27] with about 37 cubic kilometres (8.9 cu mi)[45][46]—50 cubic kilometres (12 cu mi) of volcanic rock.[27][47] The ground at Llullaillaco is formed mostly by lavic rocks and block debris, which are frequently buried bytephra.[48] The rocks are grey, except whereweathering has coloured them black, brown, red or yellow,[35] and their appearance isvitrophyric orporphyritic.[40]
Several dry valleys originate on Llullaillaco, including Quebrada de las Zorritas on the north-northeastern slope, Quebrada El Salado and Quebrada Llullaillaco on the northwestern slope, and Quebrada La Barda on the southwestern slope.[49] Most of the dry valleys drain into Salar de Punta Negra.[50] There is little erosion by water,[37] and the valley network is poorly developed.[37] There is water only episodically,[51] duringsnowmelt.[52] Only Quebrada de las Zorritas carries permanent water.[53] There is a permanentspring there,[54] possibly in Quebrada de Llullaillaco and Quebrada de Tocomar as well,[55] while there are no known springs on the Argentine side of Llullaillaco.[5] Darapsky in 1900 reported the existence of warm springs at Ojo del Llullaillaco and Ojo de Zorritas.[56]
Several small lakes are found at5,850 m elevation.[57] At6,170 m elevation on the northwestern flank is Lago Llullaillaco lake,[58] a 1.2–1.4-hectare (3.0–3.5-acre) frozen waterbody.[58] It is one of the highest lakes in the world.[59]
A majorlandslide occurred in the volcano's history during the late Pleistocene, probably triggered by volcanic activity.[60] This landslide descended the eastern-southeastern flanks of the volcano into Argentina,[2][40] first over a steep slope of 20° on the volcano,[61] split around Cerro Rosado and entered the Salina de Llullaillaco25 km east of the summit,[40] extending up to5 km into the salar.[62] The toe of the avalanche reaches a thickness of10 m above the salar in the avalanche's southern lobe. Part of the avalanche was channelled in a valley between Cerro Rosado and an unnamed volcano farther south.[63] When it reached Cerro Rosado, the avalanche climbed about400 m and mostly continued to flow southeast into the main avalanche path, with only a small flow continuing northeastwards. Part of the run-up avalanche later collapsed backward over the main avalanche deposit.[64] Unlike Socompa farther north, a landslide scar is only poorly developed at Llullaillaco despite the large size of the collapse;[65] it was largely filled in later by lava flows and volcaniclastic debris.[66]
This landslide has been subdivided into fourfacies and features landforms like levees up to50 m high,[67] longitudinal ridges and a run-up mark on Cerro Rosado.[62] Such ridges may be associated with uneven underlying terrain.[68] The surface of the slide is covered bylava bombs less than1 m long, blocks exceeding2 m width,cobbles, andgravel-like rocks.[69] The largest blocks with sizes of up to20 m are found close to the collapse scarp.[64] Overall, the margins of the landslide are very crisp and the surface covered byhummocks.[70]
The landslide deposit covers a surface of about 165 square kilometres (64 sq mi).[40] Its volume has been estimated at1–2 km3 and the speed at 45–90 metres per second (150–300 ft/s). This speed range is comparable to that of theColima,Lastarria, andMount St. Helens debris avalanches.[71] The landslide occurred no earlier than 156,000 to 148,000 ± 5,000 years ago;[40] it might coincide with the 48,000-year-old lava flow.[61] Another possibility is that the collapse took place in multiple failures.[72] Some volcanic rocks were still hot at the time of the collapse, indicating that volcanic activity occurred immediately before the collapse.[65] A smaller undated avalanche occurred on the northeastern flank.[40]
Such landslides are common at volcanoes, where they are favoured by the steep edifices that form from lava flows being stacked on top of each other. It is not usually known what triggers the collapse, althougheruption-associated earthquakes are suspected to play a role. Other volcanoes in the region with sector collapses are: Lastarria,Ollague,San Pedro, Socompa, andTata Sabaya.[73] The Mellado and Cerro Rosado volcanoes close to Llullaillaco also display evidence of sector collapses.[66]
Volcanism in the Andes is caused by thesubduction of theNazca Plate and theAntarctic Plate beneath theSouth America Plate. The Nazca Plate subducts at a speed of 7–9 centimetres per year (2.8–3.5 in/year) and the Antarctic Plate at a speed of2 cm/year. Volcanism is not continuous along the Andes; rather it occurs in four distinct volcanic zones:Northern Volcanic Zone (NVZ),Central Volcanic Zone (CVZ),Southern Volcanic Zone (SVZ) andAustral Volcanic Zone (AVZ). The formation ofmagma results from the release of water and othervolatile material from the subducting plate, which is then injected into the above-lyingmantle wedge. The volcanic zones are separated by gaps, where subduction occurs ata flatter angle due to the presence of ridges on the downgoing plate: TheNazca Ridge in the gap between the NVZ and CVZ, theJuan Fernandez Ridge in the one between the CVZ and SVZ, and the gap between the SVZ and AVZ is associated with theChile Triple Junction.[74][75] Minor ridges are associated with decreased volcanism rather than its cessation; the Taltal Ridge projects under Llullaillaco, an area where magma output was less than to the north and south.[76]
About 178Holocene volcanoes are found in theAndes, 60 of which have been active in historical times. In addition, there are largecalderas andmonogenetic volcanoes.[74]
Llullaillaco is one[77] of more than 1,000 volcanoes in the CVZ.[75] At least 44 volcanic centres with historical activity and 18 large caldera-forming volcanoes have been identified in the Central Volcanic Zone;[74] the most active isLascar,[28] andGuallatiri andSan Pedro have had historical eruptions as well.[78] Volcanism in the Central Volcanic Zone takes place mostly on theAltiplano and theCordillera Occidental,[79] where highstratovolcanoes[80] with heights of over6,000 m occur.[79] One of the largest vertical drops on Earth, almost15 km, exists between the summit of Llullaillaco and thePeru-Chile Trench300 km farther west.[81] TheWadati-Benioff zone lies at180 km depth.[82]
The region is dominated by large volcanic cones (often more than6,000 m high) in the Altiplano andWestern Cordillera,[79] and extensivesalt flats in low-altitude areas.[83] Southeast of the mountain is Salina de Llullaillaco,[84] Salar de Llullaillaco in Argentina, and Salar de Punta Negra northwest of Llullaillaco in Chile.[17] Neighbouring mountains are 4,923-metre-high Cerro Mitral southwest and 5,473-metre-high Volcan Chuculay north of Llullaillaco.[21] Cerro Rosado is17 km east of Llullaillaco;[2] it is a 5,383-metre-high volcano which erupteddacitic lava flows on its northeastern and southern flanks during thePliocene–Quaternary.[22] Mitral mountain (5,015 m) lies southwest of Llullaillaco and is of Miocene age. It features an eroded crater that opens to the northwest.[21][43] Iris mountain (5,461 m) north of Llullaillaco is constructed of Pliocene rocks.[43] Other volcanoes in the neighbourhood are Dos Naciones, Cerro Silla, and Cerro 5074.[85] Llullaillaco is associated with a localcrustal upwarp.[86] Salar de Llullaillaco is a salt pan[22]20 km east of the volcano,[24] behind Cerro Rosado. It lies at3,750 m elevation,[87] and featureswarm springs at its western and southwestern shores.[22] Due east of Salar de Llullaillaco isSalar de Arizaro.[88]
The terrain around Llullaillaco consists ofandesite and dacitelavas andpyroclastics of Miocene to Pliocene age.[22] Thebasement in the 70-kilometre-thickcrust[82] is formed byPaleozoic sedimentary and volcanic rocks, including marine and volcanic sediments andintrusive rocks.[79] It is mostly buried byCenozoic volcanic rocks, except in isolated outcrops both west and east of Llullaillaco:[89] The 282 ± 7 million-year-old Llullaillacoplutonic complex,[90] theDevonian–Carboniferous Zorritas Formation[91] andOligocene–Miocene layers in the Quebrada de las Zorritas.[92] The rocks of Llullaillaco overlie both this basement andTertiary ignimbrites.[34] The terrain around the mountain is partially covered byalluvial sediments, debris andpumice.[21]
Volcanism in the Central Andes began during theJurassic.[93] A pause in volcanism occurred between 38 and 27 million years ago;[75] about 26 million years ago, theFarallon Plate broke up into theCocos and Nazca Plates,[93] volcanism resumed in the Central Andes[75] and increased subduction of the Nazca Plate during the late Oligocene caused thevolcanic arc to broaden to about250 km. Twenty-five million years ago, the "Quechua event" triggered the uplift of the Puna-Altiplano, a highland covering a surface area of500,000 km2 and reaching an altitude of3,700 m. In the late Miocene–Pliocene a phase of strong ignimbrite volcanism occurred. About two million years ago, the "Diaguita deformation" was characterized by a change in the deformation regimen fromcrustal shortening tostrike-slip faulting and of volcanism from voluminous felsic eruptions to isolated stratovolcanoes andback-arc mafic volcanism. A slowdown in the subduction may have caused this change. Nowadays most volcanism occurs at the western edge of the Puna, where volcanoes such as Lascar and Llullaillaco formed.[77][94]
Volcanism in the Central Volcanic Zone may be affected by deep-seated lineaments, such as the Olacapato-El Toro and Archibarca lineaments,[95] which control wherevolcanoes andgeothermal systems form.[79][96] They extend diagonally across the volcanic arc and are accompanied by volcanic manifestations at substantial distances from the arc.[94] The Archibarca lineament runs[97] from theEscondida copper deposit,[98] over Llullaillaco (where it crosses the volcanic arc),[99]Corrida de Cori,Archibarca,Antofalla to theGalán caldera;[100] it influenced the development of Llullaillaco.[77] Otherfaults are the northeast–southwest trending Guanaqueros[101] and the northwest–southeast trending Imilac-Salina del Fraile; Llullaillaco formed on the trace of the latter fault.[102]
Llullaillaco has produced dacites,[35] which define a potassium- and aluminium-rich[103]calc-alkaline suite. Some rocks displayshoshonitic characteristics[104] typical for lavas erupted at large distance from the trenches.[105] Others have medium contents of potassium.[106]Phenocrysts are mostlyhornblende orpyroxene with lesser quantities ofbiotite andquartz;apatite, iron-titanium oxides, opaque minerals,sphene,sulfides andzircon are rare.[40][107] Some phenocrysts show evidence of a complex history.[104] Older rocks containhematite.[40] Elementalsulfur is found at Llullaillaco,[108] specifically at Azufrera Esperanto;[35] sulfur reserves are estimated to amount to 210,000 tonnes (210,000 long tons; 230,000 short tons).[109]
Trace element data are typical for Central Volcanic Zone rocks.[106] Rocks become morefelsic the younger they are:[106] Older rocks contain more quartz and biotite than recent ones,[110] and display higher iron and loweralkali metal contents.[103]
The composition may reflect magma differentiation in a solitarymagma chamber, but with occasional replenishment with more primitive/[106] differentiated melts.[106] Processes in the chamber such as magma mixing and crystallization ofplagioclase[111] yielded melts with homogeneous composition and lowvolatile concentrations that upon eruption formed viscous lava flows.[104] A lithospheric structure probably directed magma flows over long time periods along the same pathway,[71] and magma interacted with the crust as it ascended.[104] The depth of the magma source probably varied over the history of the volcano.[112] The total magma output at Llullaillaco is between 0.05 cubic kilometres per millennium (0.012 cu mi/ka)[47] and0.02 km3/ka.[45]
The climate in the region is cold, dry[83] and sunny.[26] There are only limited climate data from Llullaillaco.[113][114] Temperatures at the summit are about −15 °C (5 °F)[11] to −13 °C (9 °F),[11] with temperature maximums ranging from −8 °C (18 °F) in summer to −13 °C (9 °F) in winter.[115] The temperature of the ground fluctuates strongly between day and night,[116] and can reach 12.5 °C (54.5 °F) in summer.[117] The climate is extremely sunny, perhaps one of the sunniest places on Earth,[53] andUV radiation is intense.[118] The high insolation is due to the lack ofcloud cover, the high altitude, and the close coincidence betweensummer solstice with theday where Earth is closest to the Sun which boosts the maximum possible daily insolation.[26][119]
Mean annual precipitation reaches 20–50 millimetres (0.79–1.97 in),[53] decreasing from west to east,[114] and is episodic to the point that it is difficult to give average values.[120] It is most often associated with eitherconvective activity during summer orcyclones during winter.[121]Snowfall can occur down to altitudes of4,000 m.[122] TheAndean Dry Diagonal, where half of the precipitation falls in summer and the other half in winter,[24][123] crosses the Andes at Llullaillaco.[124] It and theAtacama Desert owe its existence to therainshadow effect of the Andes, air subsidence withinSouth Pacific High, and the coldHumboldt Current off the Pacific coast.[120][125] Owing to the high evaporation rates and low precipitation, the soils at Llullaillaco are among the driest on Earth.[118]
The climate has not always been uniformly dry. Between 14,000 and 9,500 years ago[75] during thelate glacial,[126] a wet period gave rise to lakes in the Altiplano[127] (Lake Tauca pluvial).[126] Water discharge from Llullaillaco and neighbouring mountains[128] into Salar de Punta Negra increased,[129] leading to the formation of standing water bodies.[130] As glaciers retreated between 15,000 and 10,000 years ago, lakes shrank.[83] Climate was extremely dry between 9,000 and 4,000 years ago[75] and temperatures warmer than today during the earlyHolocene (Holocene Climatic Optimum).[131] Deposits in Quebrada de las Zorritas valley indicate that between 2,500 and 1,600 yearsbefore presentrunoff was more intense.[132]
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It is not clear whether there areglaciers on Llullaillaco—some sources contend that there are no glaciers on Llullaillaco, which would make it the highest mountain in the world without one,[133] while others state that there are small glaciers above6,000 m altitude,[60] four permanent snowpatches[134] of glaciers on the northeastern and southern flanks,[135] or a single0.55 km2 (as of 2002[update]) glacier above6,500 m elevation.[136] In 2006 the General Water Directorate of Chile stated that there were seven separate ice bodies on the mountain, all on the northwestern side.[137] An ice slab was reported in 1958 on the western slope[138] between5,600–6,500 m elevation,[139] but it is not a glacier.[140][141] The lack of glaciers is a consequence of the dry climate,[142] as the highinsolation and dry air cause all snow to evaporate before it can form glaciers.[143]
However, Llullaillaco has permanent[14] snow fields[26] in protected niches,[6] which are not large enough to give rise to glaciers.[144] One-to-1.5-metre-highpenitentes occur above5,000 m altitude,[145] especially in more sheltered areas[146] and around the old crater.[147] Thesnowline lies at5,400–5,800 m elevation.[83] Temporary snow cover also occurs.[32] The snow and icefields on Llullaillaco reach thicknesses of 7–10 metres (23–33 ft)[148] and supply water to the Salar de Punta Negra.[149]
The occurrence of past glaciation at Llullaillaco[128][150] and its neighbours during the Pleistocene is also uncertain.[39] Some traces of past glacier activity are found in the summit area;[39]cirques may have existed on the northwestern slope,[151] where glaciers may have descended to5,100 m elevation,[152] and amoraine girdle may have formed at4,900 m elevation.[153] There is evidence ofglacial landforms destroyed by lava[48][152] and volcanicmudflows.[154] It was once believed that Llullaillaco had experienced three large glaciations,[155] but the "moraines" are actually mudflow[152]/volcanic deposits.[156] Some landforms indicate that any glaciation occurred before thelast glacial maximum.[157] Even when temperatures decreased during thelast glacial maximum, the climate at Llullaillaco may have been too dry to permit glacier development.[158] If any glacier expansion took place, it was during the late glacial when the climate was moister.[126]
Periglacial phenomena are observed on Llullaillaco, commencing at4,300 m altitude and reaching their maximum around5,100–5,400 m on the Chilean and5,350–5,700 m on the Argentine side.[122] They aresolifluction surfaces,cryoplanation surfaces, block ramparts,[159] andpatterned ground.[160]Permafrost is found at higher altitudes[122] and is connected to the snowfields.[144] Cryoplanation and solifluction landforms are also observed on Iris and Mitral.[92] The landforms probably developed during past periods where the climate was more humid.[122]
Vegetation is scarce in thearid climate,[60] especially below3,700–3,800 m altitude where precipitation is too low to permit vegetation development.[54][161] It takes the form of asteppe, with sparsecushion plants andshrubs.[57]Acantholippia punensis,Atriplex imbricata, andCristaria andicola are the first plants that grow above this elevation. They are joined at3,900 m altitude byStipa frigida which can be found up to4,910 m of altitude. The maximum vegetation density is found around4,250 m with 12% of the surface. At this altitude,Adesmia spinosissima,Fabiana bryoides,Mulinum crassifolium, andParastrephia quadrangularis are found in addition to the previously mentioned plants. Above this altitude, plant cover decreases again, probably due to low temperatures,[54][161] and disappears above5,000 m elevation;[145] most of the volcano lies above this line.[162]Deyeuxia curvula,Distichia muscoides andOxychloe andina formwetlands (bofedales) in valleys.[163]
The fauna is represented bydeer,guanacos,vicuñas[164] andvizcachas.[165] Especially around waterbodies[164] are birds like ducks,flamingos andrheas.[165] Most animals do not reach altitudes above4,600 m.[6] Ascorpion species (Brachistosternus llullaillaco) is named after the volcano.[166] There seems to be a population of thePunta de Vacas leaf-eared mouse[167] on Llullaillaco; it likely is the highest-elevation permanent population of any knownvertebrate species.[168]
Lichens grow on rocks.[58]Algae,[169] includingsnow algae[170] andcyanobacteria, live on the penitentes,[171] sometimes forming coloured patches,[172] and algae andmicrobial mats grow in Lago Llullaillaco.[173] A species ofbacterium (Subtercola vilae) was discovered in the lake.[174] The microorganisms in the lake resemble these of other Central Andean lakes, such asAguas Calientes andLake Licancabur, in some ways and differ in others.[175] Species-poorfungal and bacterial communities have been found in the soils (more precisely: tephra[176]) of Llullaillaco,[177] with the fungusNaganishia friedmanii being the most common species.[178] The soils are extremely poor inorganic matter[118] and have simple ecological communities.[179] They have to survive environmental conditions[180] among the most extreme on the planet,[181] with aridity, strong UV radiation, dailyfreeze-thaw cycles and a lack of nutrients.[168] Life may depend on unusual food sources like gaseouscarbon monoxide[180] or organic material (e.g remains of plants[168]) transported to the mountain by winds,[182] whilephotosynthetic organisms are limited to sites with higher water availability.[183]
The area of Llullaillaco is part of theLlullaillaco National Park,[184] a Chileanprotected area[185] created in 1995[9] and named after the mountain.[186] Air pollution from the Escondida copper mine may reach Llullaillaco and threaten ecosystems there.[187]
Archaeological sites on mountains are widespread in the Andes, with forty mountains featuring sites in Salta Province alone.[188] In the 1950s severalarchaeological sites were discovered on Llullaillaco.[189] The initial discovery was in 1952; further expeditions took place during the second half of the 20th century.[188] Some sites were looted after their discovery.[190]
Three Inca roads come to Llullaillaco from Salar de Llullaillaco,[191] Salar de Punta Negra and Socompa,[192] and meet[191] at atambo (inn) at an altitude of5,200 m[83] on the northeastern flank.[14] Thetambo consists of numerous buildings;[83] it was probably abase camp for ascents.[193] On the road from Salar de Llullaillaco[191] is a cemetery, where 16 bodies were found in 1972.[190] The cemetery may host the bodies of people killed in the construction of the Llullaillaco archaeological sites.[194] Half-destroyed walls[190] form a building complex, which was built on terraces[195] and partly buried by loose debris from the mountain above.[196] Twowater sites lie between the cemetery and thetambo.[83]
An Inca ceremonial path begins at thetambo and leads up the volcano. It is1.5–2 m wide (narrower in steeper reaches)[194] and marked by wooden posts[197] andcairns, probably for the case that the path is covered in snow.[83] It continues past two waystations[83] at5,600 m and6,300 m elevation, which consist of small buildings and protecting walls.[193] At6,500 m altitude, the path splits at the so-called "Portezuelo del Inca". One continues to the summit, the other to a plateau at6,715 m elevation.[83] Another set of protecting walls and small buildings form another waystation at6,550 m elevation.[193] Two enclosures and a11 m × 6 m platform are on the plateau,[83] forming the highest archaeological site on Earth.[198]
The Inca roads connect with the major north–south[199][200]Inca road[201] that runs betweenSan Pedro de Atacama andCopiapo.[200] Infrastructure such as road markers,[202] shelters[203] andtambos are found along the road close to Llullaillaco.[204] The paths on Llullaillaco are not simple footpaths but equipped with retaining walls, delimited edges[205] and staircases (above "Portezuelo del Inca").[83] They were built by the Inca,[83] their construction methods perhaps reflecting Inca mythology.[206] They were discovered by Mathias Rebitsch in 1958.[207]
Llullaillaco appears to have been the most important Incasacred mountain in the region[208] and possibly all of the Central Andes,[55] and the complex of archaeological sites is one of the most significant in the Andes.[36] In the case of Llullaillaco, they may have been sites ofpilgrimage[195] used by the localAtacama people duringInca rule,[209] no evidence of pre-Inca activity has been found.[210] About forty-five structures have been identified at Llullaillaco, distributed across several sites and with clear architectonic differences, implying not all of them were built by the state.[83] Among the structures arestone circles and roofed buildings.[211] Archeological sites are also found in the valleys that drain Llullaillaco towards the Salar de Punta Negra,[212] including the Quebrada Llullaillaco and the Quebrada de las Zorritas[213] where the Inca paths ascend the mountain.[214] The complex of archaeological sites has become subject of scientific research.[215]
Because of the findings, the summit area of the volcano in 2001 was classified as aLugar Histórico Nacional by the government of Argentina,[216] and on 24 June 2014 the entire Llullaillaco complex was declared aWorld Heritage Site by UNESCO.[217] There are myths associated with Llullaillaco,[30] and the mountain is still important to the inhabitants ofSocaire[218] east of theSalar de Atacama,[219] from where it is visible.[220] Some ascents are done for ritual reasons.[221]
In March 1999, excavations of the platform[193] by a team of archaeologists[222] led by Johan Reinhard,[223] found threemummies of children buried at1.7 m depth in partially natural, partially excavated pits.[11] They were a 7-year-old boy, a 6-year-old girl and a 15-year-old girl (later research has suggested lower ages for all three[224]),[222] which are known as "El Niño", "La Niña del Rayo" and "La Doncella", respectively.[188] They were found clothed and in a seated position[225] and were ostensibly human sacrifices offered to the gods of theIncan pantheon on mountaintops.[226] It is not clear how they were killed; most likely, they were suffocated or buried alive but unconscious,[227] and the boy may have been dead before reaching the summit.[228] The younger children bore traces ofcranial deformation.[229] The Llullaillaco bodies are among the best preserved knownpre-Columbian mummies[215] owing to the cold, dry and oxygen-poor conditions of the summit[230] which prevent microbial decay of the bodies[231]—except for the youngest mummy, which had been damaged bylightning.[222]
Inca human sacrifices were initiated for various reasons, either to mark particular events such as the death of anInca Emperor, to appease nature duringnatural disasters or to secure resources from the mountain gods. The chosen sacrifices were children, as the gods were thought to prefer pure offerings, preferably children with unblemished bodies and virgin girls. According to historical sources and analyses of the mummies, the children came from families with high social standing and were well nourished. They were brought to mountains thousands of kilometres away and killed at the top.[227][232]
Other archaeological objects found along with the mummies included: bags made out of leather,headdresses withfeathers,pottery (cooking instruments like jars, plates, pots and vases),statues representing both people (male and female) and animals made out of gold, silver orSpondylus (oyster) shells, shoes and textiles,[11][189] wooden and woollen vessels. The vessels and bags containedcoca leaves, hairs andhuman nails.[189] A total of 145 objects were found together with the mummies.[233]Radiocarbon dating has yielded a date of death of 1430–1520AD for one of the mummies.[234]
Their discovery drew interest among specialists and the public,[11] and has been cited as a cause for increased tourism to the mountain[235] and increased attention dedicated to native people issues in the region.[236] In 2003 the mummies were at theCatholic University of Salta [es],[222] before being transferred to theMuseum of High Altitude Archaeology of Argentina in 2007,[237] which had been built to host these mummies.[238] They are kept under special storage conditions to prevent damage.[239] The bodies found at Llullaillaco—both the mummies on the summit and these in the cemetery—have been subject to various scientific analyses.[240] The placement of the mummies in museums led to lengthy disputes with organizations advocating the rights of indigenous people.[241]
The volcano developed in two stages, Llullaillaco I and Llullaillaco II. The first stage originated from two centres[89] (Llullaillaco and Azufrera Esperanto) developed in a north–south line, producing up to 20-kilometre-long lava flows and lava domes in their summit regions. The cones and associated lava flows are heavily eroded by[34]glaciation andhydrothermal alteration[89] and buried by more recent volcanic rocks, but still make up about 70% of the surface of the volcano especially in its western sector. The former crater of Llullaillaco forms a plateau at5,600–6,100 m elevation.[34] At the5,561 m high Azufrera Esperanto mountain5 km north of Llullaillaco little original volcanic substance is preserved. Erosion has exposed deeply altered whiteish rock there.[34] Llullaillaco II on the southern and northeastern flank is better preserved; the toes of the lava flows reach thicknesses of500 m.[40] Its lava flows are less extensive than the ones of Llullaillaco I.[82] Pyroclastic flow deposits with a composition similar to Llullaillaco II are found on the southern slope of the volcano and may have formed before the lava eruptions began.[35]
An older unit is formed by ignimbrites andpyroclastic flows.[82] Older lava flows extend west from the volcano and are partly buried by sediments closer to the edifice.[34] The landslide probably took place during an eruption.[60] Anexplosive eruption of Llullaillaco II produced a3 km long deposit of lava blocks and pyroclastic pumice,[35][242] with fallout reaching Cerro Rosado.[42] It is possible that some lava flows interacted with glaciers, causing them to melt,[152] and volcanic rocks overran glacial[243] and periglacial landforms.[244]
The oldest-dated rocks at Llullaillaco were erupted 1.5 ± 0.4 million years ago, forming a lava flow northwest of Llullaillaco's main edifice.[21] Llullaillaco I is of early Pleistocene age,[89] but the time of the transition between Llullaillaco I and Llullaillaco II is unclear: Either it took place 450,000 years ago,[30] or less than 41,000 ± 1,000 years ago. Ages of 5,600 ± 250 years have been obtained for Llullaillaco II rocks recovered at an altitude of over6,000 m.[152] The young-looking lava flows were at first thought to be of Holocene age, but[2] dating methods yielded ages of less than one million years (potassium–argon dating) for the northern flow, 48,000 ± 12,000 years (argon–argon dating)[40] on the southwestern flow[18] and 930 ± 140 years (surface exposure dating) on a different flow.[245]
Llullaillaco has been active in historical time, making it the highest historically active volcano on Earth.[2] Three eruptions were recorded during the 19th century,[246] which were, however, not directly observed[247] and are unconfirmed:[248]
Activity was probably limited to the emission of steam and ash, given the presence of the archaeological sites.[252] Other reports mention eruptions in 1920, 1931, 1936 and 1960.[242]
According to anecdotes recorded in the 19th century, the mountain occasionally smoked,[253][254] including during the mapping of the Chile-Argentina border on 5 May 1879.[255] Allegedly palaeontologist and zoologistRodolfo Amando Philippi saw the mountain smoke in 1854,[253] but Philippi's own report makes no mention of smoke.[256]
The volcano is currently considereddormant[27] and there are no knownfumaroles,[257] but Lago Llullaillaco[168] and some ice on the volcano bear traces of geothermal heating.[147] There arewarm springs around Salar de Llullaillaco.[258] Llullaillaco is classified as being mid-range in terms of dangerousness to Argentina,[259] being its 16th-most-dangerous volcano in a list of 38.[260] Future eruptive activity may result in the emission of pyroclastic flows and lava flows[242] and may causesector collapses, although they would be a small danger to life or property, given that the area is sparsely inhabited and largely devoid of economic activity.[61][261]
The easiest ascent is along the former Inca route on the northeastern flank of the mountain,[262] which can be reached from Chile.[223] The intense UV radiation,[263] lack of oxygen,[57]blizzards,hypothermia and lightning are common hazards at Llullaillaco.[6] There are reports oflandmines in the area;[223] the mines were removed in 2006 thanks to a multinational effort.[264] A new base camp was inaugurated in 2020.[265]
The volcano can be reached from Argentina viaTolar Grande.[235] Access from Chile is through roads which fromChile Route 5,Socompa Pass,Taltal orToconao lead to Salar de Punta Negra.[266] From there, a road leads to Llullaillaco. It splits at Aguada de las Zorritas in three: One road ends close to a mountain pass north of Llullaillaco, a second ends at Azufrera Esperanto and the third rounds the volcano from southwest, crossing into Argentina south of Llullaillaco.[21] According to John Biggar, some roads are dead ends. Two ascent routes with camps lead from Chile and Argentina to the summit.[267]
The first known ascent byWesterners was by the Chileans Bion González and Juan Harsheim in 1952[223] but the indigenous people had ascended it long before. The volcano is the highest mountain with proven prehistoric ascents[268][269] and demonstrates that high altitudes were no obstacle to indigenous people in the Americas,[270] who also built on mountains with primitive technology.[271]
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