Llullaillaco () is a dormant stratovolcano at the border of

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

( Salta Province) and

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

(

Antofagasta Region The Antofagasta Region ( es, Región de Antofagasta, ) is one of Chile's sixteen first-order administrative divisions. The second-largest region of Chile in area, it comprises three provinces, Antofagasta, El Loa and Tocopilla. It is bordered t ...

). It lies in the

Puna de Atacama The Puna de Atacama or Atacama Plateau''Atacama Plateau''
article at the ''

plateau In geology and physical geography, a plateau (; ; ), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Often one or more sides ...

close to the

Atacama Desert The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in th ...

, one of the driest places in the world. It is the second highest active volcano in the world after

Ojos del Salado Nevado Ojos del Salado is a dormant complex volcano in the Andes on the Argentina–Chile border. It is the highest volcano on Earth and the highest peak in Chile. The upper reaches of Ojos del Salado consist of several overlapping lava domes, ...

. Llullaillaco formed during two different phases in the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

out of

dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyol ...

lava flows. The oldest rocks are about 1.5 million years old. About 150,000 years ago, the volcano's southeastern flank collapsed, generating a debris avalanche that reached as far as from the summit. The youngest dated rocks were erupted 5,600 ± 250 years ago in the summit region, but there are reports of activity from the 19th century. The mountain's first recorded climb was in 1950, but traces of earlier climbs and a number of archaeological sites were found on the mountain and at its feet; Llullaillaco marks the highest archaeological site in the world. In 1999, the

mummified A mummy is a dead human or an animal whose soft tissues and organs have been preserved by either intentional or accidental exposure to chemicals, extreme cold, very low humidity, or lack of air, so that the recovered body does not decay furt ...

remains of three children, known as the Children of Llullaillaco, were found at its summit. They are presumed to have been

human sacrifice Human sacrifice is the act of killing one or more humans as part of a ritual, which is usually intended to please or appease gods, a human ruler, an authoritative/priestly figure or spirits of dead ancestors or as a retainer sacrifice, wherein ...

s. Mice have been observed in the summit region, they are the highest finding of a mammal in the world.

Name

The name ''Llullaillaco'' is derived from the

Quechua Quechua may refer to: *Quechua people, several indigenous ethnic groups in South America, especially in Peru *Quechuan languages, a Native South American language family spoken primarily in the Andes, derived from a common ancestral language **So ...

word meaning "false", "lie" or "deceitful" and or meaning "water". This name probably refers to the meltwater from snow, which flows down the slopes but then is absorbed into the soil; normally mountains are sources for water. It is possible that it instead refers to the precipitation regime, which starting from Llullaillaco becomes dominated by winter precipitation. Another translation in

Aymara Aymara may refer to: Languages and people * Aymaran languages, the second most widespread Andean language ** Aymara language, the main language within that family ** Central Aymara, the other surviving branch of the Aymara(n) family, which today ...

is "hot water".

Geography and geology

Volcanism in the Andes is caused by the subduction of the Nazca Plate and the

Antarctic Plate The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau, and some remote islands in the Southern Ocean and other surrounding oceans. After breakup from Gondwana (the southern part of the superconti ...

beneath the

South America Plate The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mid-A ...

. The Nazca Plate subducts at a speed of and the Antarctic Plate at a speed of . Volcanism does not occur along a continuous chain; there are four separate regions named: the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone, and the Austral Volcanic Zone. The formation of

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

results from the release of

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

and other volatile material from the subducting plate, which is then injected into the above-lying

mantle wedge A mantle wedge is a triangular shaped piece of mantle that lies above a subducting tectonic plate and below the overriding plate. This piece of mantle can be identified using seismic velocity imaging as well as earthquake maps. Subducting oceanic ...

. The volcanic zones are separated by areas where the subducting plate subducts at a flatter angle and volcanism is absent. The Peruvian flat slab between the Northern and the Central Volcanic Zones is associated with the subduction of the Nazca Ridge, the Pampean flat slab between the Central and the Southern Volcanic Zone is associated with the subduction of the Juan Fernandez Ridge, and the Patagonian volcanic gap between the Southern and the Austral Volcanic Zone is associated with the Chile Triple Junction. About 178 volcanoes are found in the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

, 60 of which have been active in historical times. In addition, large

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

s and monogenetic volcanoes exist in the Andes.

Local setting

Llullaillaco is part of the Central Volcanic Zone. At least 44 volcanic centres with historical activity and 18 large caldera-forming volcanoes have been identified in the Central Volcanic Zone. Volcanism in the Central Volcanic Zone mostly occurs on the

Altiplano The Altiplano (Spanish for "high plain"), Collao (Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located at the ...

and the Cordillera Occidental. A number of volcanoes there reach heights of over above sea level. Large

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...

s that cover large surfaces are also part of the regional geology. Llullaillaco is located about east of the Peru-Chile Trench. The Wadati-Benioff zone lies at depth. Llullaillaco is located in the northwestern Argentine Andes, towards the southern end of the Puna. It lies in the

Puna de Atacama The Puna de Atacama or Atacama Plateau''Atacama Plateau''
article at the ''

close to the

, one of the driest places in the world. The border between

( Salta Province) and Chile crosses the volcano. Paranal Observatory and the Volcano Llullaillaco

The volcano is an imposing mountain, rising by above the Salar de Punta Negra away. With a summit height of , or alternatively or , it is the second highest active volcano in the world after

(, ). The height of the mountain and the clear air in the region make Llullaillaco visible from Cerro Paranal, away as measured by

Google Maps Google Maps is a web mapping platform and consumer application offered by Google. It offers satellite imagery, aerial photography, street maps, 360° interactive panoramic views of streets ( Street View), real-time traffic conditions, and rou ...

. In return, the Nevados de Cachi mountains

farther south is visible from Lllullaillaco. The region is dry and located at high altitudes, making work in the area difficult. farther east of Llullaillaco lies the Miocene Cerro Rosado volcano (). It erupted

lava flows on its northeastern and southern flanks during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Quaternary. east of Llullaillaco, and behind Cerro Rosado is the Salar de Llullaillaco ( ), a salt pan with warm springs at its western and southwestern shores. There are three abandoned

borate A borate is any of several boron oxyanions, negative ions consisting of boron and oxygen, such as orthoborate , metaborate , or tetraborate ; or any salt with such anions, such as sodium metaborate, and disodium tetraborate . The name also re ...

mines Mina Amalia and the

salt mine Salt mining extracts natural salt deposits from underground. The mined salt is usually in the form of halite (commonly known as rock salt), and extracted from evaporite formations. History Before the advent of the modern internal combustio ...

s Mina Luisa and Mina Maria and the recent

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...

prospect "Proyecto Mariana" at Salar de Llullaillaco. Mitral mountain () lies southwest of Llullaillaco and is of Miocene age. It features an eroded crater that opens to the northwest. Iris mountain () north of Llullaillaco is constructed of Pliocene rocks. Other volcanoes in the neighbourhood are Dos Naciones, Cerro Silla, and Cerro 5074. Llullaillaco is associated with a local crustal upwarp.

The volcano

Llullaillaco is a stratovolcano which rises above the surrounding terrain. The edifice has an elliptical shape with dimensions of and has a volume of about -. It is formed by thick dacitic lava flows erupted during the Quaternary. These flows extend away from the volcano and form its summit. An older unit is formed by ignimbrites and

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...

s. Older lava flows extend west from the volcano and are partly buried by sediments closer to the edifice. These flows reach lengths of and form about 70% of the surface of the volcano. The slopes of the volcano are fairly steep, with an altitude drop of over only horizontal distance. The slopes high up are steeper than those at lower altitudes. A crater at altitude was formed early in the development of the Llullaillaco volcano. Erosion has reduced it to a plateau. This crater is filled with snow and ice. The ice shows evidence of recent geothermal heating. Llullaillaco Volcano, Argentina-Chile Border 2009-12-09

Llullaillaco Volcano, Argentina-Chile Border 2009-12-09

The summit of Llullaillaco is formed by a small cone with about four associated lava domes, which reach lengths of and have abrupt walls. Large dacitic

coulee Coulee, or coulée ( or ) is a term applied rather loosely to different landforms, all of which refer to a kind of valley or drainage zone. The word ''coulee'' comes from the Canadian French ''coulée'', from French ''couler'' 'to flow'. The ...

s emanate from the summit of the volcano and are young in appearance. One extends north of the volcano and the other one south. Their overall length is and their flow fronts are up to thick. Morphologically, these flows are reddish-black

aa lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

flows and feature blocks with sizes of . The southern lava flow is long and was fairly viscous when it was erupted. It almost reaches a road southwest of the volcano. These flows feature levees and ridges. At first they were considered to be Holocene, but argon-argon dating indicates they are of late Pleistocene age. Some traces of

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

activity are found in the summit area. At least two stages of construction are recognized, Llullaillaco I and Llullaillaco II. The first stage originated from two centres and is now extensively degraded by

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...

and

hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical co ...

. This applies especially to the high Azufrera Esperanto mountain north of Llullaillaco, where little original volcanic substance is preserved and where erosion has exposed deeply altered white rock. Llullaillaco II on the southern and northeastern flank is better preserved; the toes of the lava flows reach thicknesses of . Its lava flows are less extensive than the ones of Llullaillaco I. 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. Volcanism in the Central Volcanic Zone may be affected by deep-seated lineaments, which control where

volcano A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ear ...

es and geothermal systems form. Such lineaments extend diagonally across the volcanic arc and are accompanied by volcanic manifestations at substantial distances from the arc. One of these lineaments, the Archibarca, runs beneath Llullaillaco and is also associated with the

Escondida Escondida is a copper mine at elevation in the Atacama Desert in Antofagasta Region, Chile. Geology The Escondida deposit is one of a cluster of porphyry coppers in an elongated area about 18 km north–south and 3 km east–west a ...

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

deposit, Corrida de Cori, Archibarca,

Antofalla Antofalla is a Miocene-Pliocene volcano in Argentina's Catamarca Province. It is part of the volcanic segment of the Andes in Argentina, and it is considered to be part of the Central Volcanic Zone, one of the volcanic zones of the Andes. Anto ...

, and the Galán caldera. Other lineaments include the Calama-El Toro. 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. The Quebrada Llullaillaco drains into the Salar de Punta Negra northwest of the volcano. The volcano is relatively unaffected by water erosion, water is only episodically present on the mountain. On the northwestern flank there is a lake called the "Lago Llullaillaco" on the mountain; with an elevation of it is one of the highest lakes in the world. Two abandoned sulfur mines can be found north and south of Llullaillaco. The northern mine is known as Azufrera Esperanto and associated with an area of hydrothermal alteration. A path or road leads up to that mine from northwest. Llullaillaco Sunset.jpg, Llullaillaco during sunset Parque Nacional Llullaillaco, Chile.jpg, Llullailaco with a road leading to the mountain. Llullaillaco from Base Camp on western slopes. See bobvillarreal.com for more..jpg, Llullaillaco from the base camp. Llullaillaco 2.jpg, Lava flow from Llullaillaco Llullaillaco 1.jpg, Llullaillaco in Salta

Debris avalanche

A major landslide occurred in the volcano's history during the late Pleistocene, probably triggered by volcanic activity. This landslide descended the eastern-southeastern flanks of the volcano into Argentina, first over a steep slope of 20° on the volcano, split around Cerro Rosado and entered the Salina de Llullaillaco east of the summit, extending up to into the salar. The toe of the avalanche reaches a thickness of 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. When it reached Cerro Rosado, the avalanche climbed about 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 backwards over the main avalanche deposit. Unlike

Socompa Socompa is a large stratovolcano at the border of Argentina and Chile with an elevation of metres. Part of the Chilean and Argentine Andean Volcanic Belt (AVB), it is part of the Central Volcanic Zone, one of the various segments of the AVB. Th ...

farther north, a landslide scar is only poorly developed at Llullaillaco despite the large size of the collapse; it was largely filled in later by lava flows and volcaniclastic debris. This landslide has been subdivided into four facies and features landforms like levees up to high, longitudinal ridges and a run-up mark on Cerro Rosado. Such ridges may be associated with uneven underlying terrain. The surface of the slide is covered by

lava bomb A volcanic bomb or lava bomb is a mass of partially molten rock (tephra) larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. Because volcanic bombs cool after they l ...

s less than long, blocks exceeding width, cobbles, and gravel-like rocks. Close to the collapse scarp on Llullaillaco the largest blocks with sizes of up to are found. Overall, the margins of the landslide are very crisp and the surface covered by

hummock In geology, a hummock is a small knoll or mound above ground.Bates, Robert L. and Julia A. Jackson, ed. (1984). “hummock.” Dictionary of Geological Terms, 3rd Ed. New York: Anchor Books. p. 241. They are typically less than in height and ...

s. The landslide deposit covers a surface of about . Its volume has been estimated at and the speed at . This speed range is comparable to that of the

Colima Colima (), officially the Free and Sovereign State of Colima ( es, Estado Libre y Soberano de Colima), is one of the 31 states that make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima. Colima i ...

, Lastarria, and

Mount St. Helens Mount St. Helens (known as Lawetlat'la to the indigenous Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United St ...

debris avalanches. The landslide occurred no later than 156,000 – 148,000 ± 5,000 years ago, it might coincide with the 48,000 year old lava flow. Some volcanic rocks were still hot at the time of the collapse, indicating that volcanic activity occurred immediately before the collapse. A smaller undated avalanche occurred on the northeastern flank. 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, although eruption-associated earthquakes are suspected to play a role. Other volcanoes in the region with sector collapses are: Lastarria, Ollague, San Pedro, Socompa, and Tata Sabaya. The Mellado and Cerro Rosado volcanoes close to Llullaillaco also display evidence of sector collapses.

Glaciers and periglacial phenomena

In 2006 the General Water Directorate of Chile stated that there were seven separate ice bodies on the mountain. Small glaciers are found above altitude. Other sources contend there are no glaciers on Llullaillaco, which would make it the highest mountain in the world without one; although the existence of an ice slab on the western slope was reported in 1958 between elevation and in 1992 there was an ice body which however lacked all evidence of glacial motion. However, Llullaillaco has snow fields tied to permafrost in the ground. high penitentes occur above altitude, especially in more sheltered areas. high penitentes were observed in 1954.

Snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...

covers the terrain above altitude.

Gullies A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble lar ...

that are found in the area probably result from meltwater runoff. The snowfields on Llullaillaco supply water to the Salar de Punta Negra. The lack of glaciers is a consequence of the dry climate, as the high insolation and dry air allow all snow to evaporate before it can form glaciers. The existence of a cirque on the northwestern slope has been postulated. It was once believed that Llullaillaco had experienced three large glaciations, but the " moraines" are actually

mudflow A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significa ...

deposits. However, during the Pleistocene glaciers reached down to altitude on the northwestern slope. Lava flows have overrun some of the glaciated surfaces and it is possible that lava flows induced the melting of glaciers. A number of glacial landforms elsewhere were destroyed by mudflows during the time of Llullaillaco's last activity. Llullaillaco may not have been glaciated at all during the Pleistocene.

Periglacial Periglaciation (adjective: "periglacial", also referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing of snow in areas of permafrost, the runoff from which refreezes in ice wedges and o ...

phenomena are observed on Llullaillaco, commencing at altitude and reaching their maximum around on the Chilean and on the Argentine side. There,

solifluction Solifluction is a collective name for gradual processes in which a mass moves down a slope ("mass wasting") related to freeze-thaw activity. This is the standard modern meaning of solifluction, which differs from the original meaning given to it ...

and cryoplanation surfaces are developed, including lobe-shaped ground and block ramparts. These landforms have been mapped on the northwestern side of the volcano. Patterned ground is also common. Permafrost is found at higher altitudes. Cryoplanation and solifluction landforms are also observed on Iris and Mitral. Other than on periglacially influenced terrain, the ground at Llullaillaco is formed mostly by lavic rocks and block debris, which are frequently buried by

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they re ...

Composition

Llullaillaco has mostly erupted dacites with medium

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

content, with rocks becoming more felsic the younger they are. Rock samples taken from Llullaillaco are mostly porphyritic or vitrophyric, with a glassy or microcrystalline matrix.

Phenocryst 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...

s are mostly

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...

, with

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...

phenocrysts being dominated by orthopyroxene and smaller amounts of biotite,

clinopyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe I ...

, and

hornblende Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rock ...

Ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With th ...

, and sulfide minerals are also present, magnetite especially in the more oxidized older lavas. Some phenocrysts show evidence of a complex history.

Quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

is rare. Older lavas have developed a red colour and contain oxidized iron in form of hematite. Lavas from Llullaillaco I are grey. The content of is 65–67%. The rocks belong to the

calc-alkaline The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic m ...

series. Trace element data are typical for Central Volcanic Zone rocks. High potassium content is typical for

shoshonite Shoshonite is a type of igneous rock. More specifically, it is a potassium-rich variety of basaltic trachyandesite, composed of olivine, augite and plagioclase phenocrysts in a groundmass with calcic plagioclase and sanidine and some dark-colored v ...

-like lavas erupted at large distance from the trenches. The composition may reflect magma differentiation in a solitary

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it up ...

, but with occasional replenishment with more primitive magma. Magma mixing and plagioclase crystallization occurred in it. A lithospheric structure probably directed magma flows over long time periods along the same pathway. The depth of the magma source probably varied over the history of the volcano. The total magma output at Llullaillaco is about -.

Geological history

The terrain around Llullaillaco consists of

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predo ...

and

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

s and pyroclastics of Miocene to Pliocene age. Some Oligocene-Miocene layers are exposed in the Quebrada de las Zorritas. Dates obtained by argon-argon dating range between 11.94 ± 0.13 and 5.48 ± 0.07 million years ago. west of Llullaillaco do

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

s and volcanite rocks crop out. Elsewhere these layers are buried by Cenozoic rocks. There are several faults in the region, such as the Imilac-Salina del Fraile

lineament ''See also Line (geometry)'' A lineament is a linear feature in a landscape which is an expression of an underlying geological structure such as a fault. Typically a lineament will appear as a fault-aligned valley, a series of fault or fold-ali ...

whose movement has influenced the activity of Llullaillaco. Research by J.P. Richards and M. Villeneuve has allowed the determination of the geological history of the region. Had volcanism during the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

and Oligocene been centered on the Precordillera, increased subduction of the Nazca Plate during the late Oligocene caused the

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...

to broaden to about . 25 million years ago, the "Quechua event" triggered the uplift of the Puna-Altiplano, a highland covering a surface area of and reaching an altitude of . In the late Miocene-Pliocene a phase of strong ignimbrite volcanism occurred. About 2 million years ago, the "Diaguita deformation" was characterized by a change in the deformation regimen from

crustal shortening Thrust tectonics or contractional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the shortening and thickening of the crust or lithosphere. It is one of the three main types of tectonic regime, ...

to strike-slip faulting and of volcanism from voluminous felsic eruptions to isolated stratovolcanoes and

back-arc A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most o ...

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 A lascar was a sailor or militiaman from the Indian subcontinent, Southeast Asia, the Arab world, British Somaliland, or other land east of the Cape of Good Hope, who was employed on European ships from the 16th century until the middle of the ...

and Llullaillaco formed.

Climate and biota

The climate at Llullaillaco is cold and dry. The average temperature is about , with temperature maximums ranging between summer and winter. Ground temperatures however can reach during the day in summer. The temperature of the ground fluctuates strongly during the day. Llullaillaco in 2004 became the site of the highest

weather station A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include tempera ...

in the world. The climate is extremely sunny on account of the lack of a cloud cover, the high altitude, and the close coincidence between summer solstice with the day where Earth is closest to the Sun. Snowfall can occur down to altitudes of . Precipitation is episodic to the point that it is difficult to give average values. It is most often associated with either

convective Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

cyclonic In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anti ...

activity during summer and winter respectively. Between 24 and 25° degrees southern latitude the Andean Dry Diagonal crosses the Andes. At this latitude, half of the precipitation falls in summer and the other half in winter. The formation of this dry diagonal is an effect both of the

rainshadow effect A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is carri ...

of the Andes, air subsidence within South Pacific High, and the cold Humboldt Current off the Pacific coast. This is the reason why the

exists. The extremely arid climate at Llullaillaco is also a consequence of these climatic effects. Vegetation is scarce in the

arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ...

climate. Vegetation at Llullaillaco begins at altitude with '' Acantholippia punensis'', '' Atriplex imbricata'', and '' Cristaria andicola''. They are joined at altitude by '' Stipa frigida'' which can be found up to of altitude. The maximum vegetation density is found around with 12% of the surface and decreases thereafter, probably due to the low temperatures. At this altitude, '' Adesmia spinosissima'', ''

Fabiana bryoides Fabiana may refer to: * ''Fabiana'' (plant), a genus of evergreen shrubs ** ''Fabiana imbricata ''Fabiana imbricata'', vernacular names pichi or false heath, is a species of flowering plant in the family Solanaceae, native to dry upland sl ...

'', '' Mulinum crassifolium'', and '' Parastrephia quadrangularis'' are found in addition to the previously mentioned plants. Above elevation there is no vegetation. Mice were filmed at in 2013, and an expedition in February 2020 found mice all the way to the summit, where a mouse of the species ''

Phyllotis xanthopygus The yellow-rumped leaf-eared mouse (''Phyllotis xanthopygus'') otherwise known as the Patagonian leaf-eared mouse is a species of rodent in the family Cricetidae and order Rodentia. It is the most widespread member of the genus. Description ''Ph ...

'' was captured. This is the highest altitude in the world at which a mammal has been found to live. Weakly developed

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

and

bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

communities have been found in the soils at Llullaillaco, with better developed

algal Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

and cyanobacterial communities found on the penitentes; some soil microbes may depend on volcanic

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

Alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

e, lichens,

microbial mat A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts ...

s and

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They ...

s grow around and in Lago Llullaillaco. The environmental conditions in these soils are among the most extreme on the planet, with aridity, strong

UV radiation Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

, daily

freeze-thaw Frost weathering is a collective term for several mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes such as frost shattering, frost wedg ...

cycles and a lack of nutrients. Organic material transported on the mountain by winds may be the principal source of food for some of these microorganisms.

Air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...

from the

copper mine may reach Llullaillaco and threaten ecosystems there.

Dry valley A dry valley may develop on many kinds of permeable rock, such as limestone and chalk, or sandy terrains that do not regularly sustain surface water flow. Such valleys do not hold surface water because it sinks into the permeable bedrock. There ...

s and sheltered areas feature

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...

es. A permanent

spring Spring(s) may refer to: Common uses * Spring (season) Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...

is found in Quebrada de las Zorritas. Deposits in this valley indicate that between 2,436.8 ± 49 and 1,593.1 ± 36

radiocarbon Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and c ...

years ago

runoff Runoff, run-off or RUNOFF may refer to: * RUNOFF, the first computer text-formatting program * Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed * Runoff or run-off, a stock marke ...

was more intense. Casualidad C 23.jpg, Llullaillaco from Salar Rio Grande Salar de Aguas Calientes IV, Región de Antofagasta.JPG, Llullaillaco from Salar de Aguas Calientes IV

Archaeology

Llullaillaco was first climbed by Inkas centuries ago. In 1999, a team of archeologists, led by Johan Reinhard, found three

mummies A mummy is a dead human or an animal whose soft tissues and organs have been preserved by either intentional or accidental exposure to chemicals, extreme cold, very low humidity, or lack of air, so that the recovered body does not decay furt ...

of children on the top of Llullaillaco. At the time of their death they were six, seven, and fifteen years old. They were ostensibly human sacrifices offered to the gods of the

Incan The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, (Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The admin ...

pantheon on mountaintops. In 2003 they were at the Catholic University of Salta, but starting from 2007 they can be found at the Museum of High Altitude Archaeology of Argentina. The mummies were found buried beneath an large platform. The existence of ruins in the summit area had been reported during the first modern climb of the volcano in 1950. Because of the findings, the summit area of the volcano in 2001 was classified as a ' by the government of Argentina. Other archeological objects found along with the mummies included:

headdresses Headgear, headwear, or headdress is the name given to any element of clothing which is worn on one's head, including hats, helmets, turbans and many other types. Headgear is worn for many purposes, including protection against the elements, d ...

with feathers,

pottery Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard and durable form. Major types include earthenware, stoneware and ...

statues A statue is a free-standing sculpture in which the realistic, full-length figures of persons or animals are carved or cast in a durable material such as wood, metal or stone. Typical statues are life-sized or close to life-size; a sculpture t ...

made out of

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...

and

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

and

textile Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...

s. A total of 145 objects were found together with the mummies. The hairs found with the mummies and as offerings accompanying the mummies have been subject of research to establish the background of the victims. Chozas dobles

At least three paths lead up to Llullaillaco. Two of them meet at a '' tambo'' or inn at an altitude of , while the third passes through a ''cementerio'' (

cemetery A cemetery, burial ground, gravesite or graveyard is a place where the remains of dead people are buried or otherwise interred. The word ''cemetery'' (from Greek , "sleeping place") implies that the land is specifically designated as a buri ...

) where 16 bodies were found in 1972 before reaching the ''tambo''. From the ''tambo'' another path leads up the mountain, past two further archeological sites to of altitude. This path is an Inca ceremonial path with an initial width of , narrowing in steeper reaches. The path is marked by cairns, probably to indicate where the path is when the volcano is covered by snow. The path ends at altitude at the Portezuelo del Inca ruins, where a staircase begins. From these ruins one path goes to a cemetery at altitude and another to the summit platform. The other path reaches two subrectangular walls farther up, and continues to the platform where the mummies were found. These are the highest archeological sites in the world. The paths were discovered by Mathias Rebitsch in 1958. Llullaillaco appears to have been the most important Inca

sacred mountain Sacred mountains are central to certain religions, and are usually the subjects of many legends. For many, the most symbolic aspect of a mountain is the peak because it is believed that it is closest to heaven or other religious realms. Many rel ...

in the region. Archeological sites are also found in the valleys that drain Llullaillaco towards the Salar de Punta Negra, including the Quebrada Llullaillaco and the Quebrada de las Zorritas. The paths connect with the major north–south axis that runs between

San Pedro de Atacama San Pedro de Atacama is a Chilean town and commune in El Loa Province, Antofagasta Region. It is located east of Antofagasta, some 106 km (60 mi) southeast of Calama and the Chuquicamata copper mine, overlooking the Licancabur volcano. ...

and Copiapo. This axis is associated with the extensive Inca road system.

Eruptive history

The volcano is about 1.45 ± 0.41 million years old, and Llullaillaco I is of early Pleistocene age. The oldest date, 1.5 ± 0.4 million years ago, was determined on a lava flow northwest of Llullaillaco's main edifice. Two dates obtained on lava flows of Llullaillaco II are 401,000 ± 6,000 and 1,500,000 ± 400,000 years ago, based on argon-argon dating and potassium-argon dating respectively. The northern young lava flow is less than one million years old based on potassium-argon dating, the southern flow is 48,000 ± 12,000 years old based on argon-argon dating on biotite.

Surface exposure dating Surface exposure dating is a collection of geochronological techniques for estimating the length of time that a rock has been exposed at or near Earth's surface. Surface exposure dating is used to date glacial advances and retreats, erosion histo ...

based on

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

has yielded ages of 41,000 ± 1,000 years for Llullaillaco I at over altitude, of 5,600 ± 250 years for Llullaillaco II at an altitude of over and of 930 ± 140 years. Llullaillaco has been active in historical time, with the last eruption occurring in the late 19th century. Eruptions were recorded in February 1854, September 1868, and May 1877, involving two explosive eruptions and one with lava flows. According to a report in 1899, during the 1868 eruption large fissures opened on its slopes. The last eruption consisted of smoking reported at the time of the

1877 Iquique earthquake The 1877 Iquique earthquake occurred at 21:16 local time on 9 May (0:59 on 10 May UTC). It had a magnitude of 8.5 on the surface wave magnitude scale. Other estimates of its magnitude have been as high as 8.9 and 9.0 (based on the size of the ...

. Other reports mention eruptions in 1920, 1931, 1936 and 1960. The volcano is currently considered dormant and there are no known

fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

s. Llullaillaco is considered Argentina's 16th most dangerous volcano out of 38. Future eruptive activity may result in the emission of pyroclastic flows and lava flows and may cause

sector collapse A sector collapse is the collapse of a portion of a volcano due to a phreatic eruption, an earthquake, or the intervention of new magma. Occurring on many volcanoes, sector collapses are generally one of the most hazardous volcanic events, and will ...

s, although they would be a small danger to human life, given that the area is sparsely inhabited.

References

Sources

* * * * * * * * * * * * * * * *

Bibliography

* * Reinhard, Johan: ''The Ice Maiden: Inca Mummies, Mountain Gods, and Sacred Sites in the Andes''. National Geographic Society, Washington, D.C., 2005. * Reinhard, Johan and Ceruti, María Constanza: "Inca Rituals and Sacred Mountains: A Study of the World's Highest Archaeological Sites" Los Angeles: UCLA, 2010. * Reinhard, Johan and Ceruti, María Constanza: ''Investigaciones arqueológicas en el Volcán Llullaillaco: Complejo ceremonial incaico de alta montaña''. Salta: EUCASA, 2000. * * Ceruti, María Constanza: ''Llullaillaco: Sacrificios y Ofrendas en un Santuario Inca de Alta Montaña''. Salta: EUCASA, 2003. * * Beorchia, Antonio: "El cementerio indígena del volcán Llullaillaco." ''Revista del Centro de Investigaciones Arqueológicas de Alta Montaña'' 2: 36–42, 1975, San Juan. * *
Complete description, history, place name and routes of Llullaillaco in Andeshandbook

Museum of High Mountain Archaeology
*

External links

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