Lascar is a

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

within the

Central Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca plate and Antarctic plate underneath the South Americ ...

of the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

, a

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 ...

that spans

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and Chile. It is the most active volcano in the region, with records of eruptions going back to 1848. It is composed of two separate cones with several summit craters. The westernmost

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

of the eastern cone is presently active. Volcanic activity is characterized by constant release of

volcanic gas Volcanic gases are gases given off by active (or, at times, by dormant) volcanoes. These include gases trapped in cavities (Vesicular texture, vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from ...

and occasional

vulcanian eruption A Vulcanian eruption is a type of volcanic eruption characterized by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak. They usually commence with phreatomagmatic eruptions which can be extremely noisy due t ...

s. Lascar has been active since at least 56,000 years ago, though some argue for activity beginning 220,000 years ago. The first known activity occurred at the eastern cone and was characterized by lava flows, before shifting to the western cone where lava domes were emplaced. An eruption event known as Piedras Grandes was followed by the large Soncor eruption. A new western edifice was constructed on top of the Soncor vent, during the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

activity then shifted again to the eastern edifice and continues there to this day. The

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

supplied to the volcano ultimately comes from the

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

of the

Nazca Plate The Nazca plate or Nasca plate, named after the Nazca region of southern Peru, is an oceanic list of tectonic plates, tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru– ...

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 number of other volcanoes are found in the region, such as

Aguas Calientes Agua Caliente, Aguas Calientes or Aguascalientes (Spanish for 'hot/warm water(s)' or 'hot spring(s)') may refer to: Places Central America * Agua Caliente, El Salvador * San Antonio Aguas Calientes, Guatemala Mexico * Aguascalientes, a state in M ...

, Cordon de Puntas Negras and the giant

La Pacana La Pacana is a Miocene age caldera in northern Chile's Antofagasta Region. Part of the Central Volcanic Zone of the Andes, it is part of the Altiplano-Puna volcanic complex, a major caldera and silicic ignimbrite volcanic field. This volcanic f ...

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

. The volcano experienced at least three major eruptions throughout its history: One is the Soncor eruption about 26,450 ± 500 years ago, another in 7,250

BCE Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the o ...

and the third in 1993. The first of these eruptions released of material and is known as the Soncor eruption. The largest eruption of Lascar known to recorded history occurred in April 1993 and caused

ash fall Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to re ...

as far away as

Buenos Aires Buenos Aires, controlled by the government of the Autonomous City of Buenos Aires, is the Capital city, capital and largest city of Argentina. It is located on the southwest of the Río de la Plata. Buenos Aires is classified as an Alpha− glob ...

. Because Lascar is located in a remote area, it is monitored primarily by

remote sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...

Explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...

s are the greatest hazard at Lascar.

Etymology

The name originates from the

Atacameño The Atacama people, also called Atacameño, are an Indigenous people from the Atacama Desert and altiplano region in the north of Chile and Argentina and southern Bolivia, mainly the Antofagasta Region. According to the Argentinean Census in 2010 ...

word ''láskar'' or ''lassi'' (), thought to refer to the shape of the volcano. Other names for the volcano are Hlàscar, Hlascar, Ilascar, Kar Las, Laskar, Toconado and Toconao.

Human use

The new town of Talabre is west of Lascar. , it had a population of 50 inhabitants.

Toconao Toconao is a village south of San Pedro de Atacama in the San Pedro de Atacama province of Chile's northern Antofagasta Region. It lies at an elevation of above sea level, close to the northeast margin of the Salar de Atacama Salar de Atacama, ...

and

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 volcan ...

lie and from the volcano, respectively. ,

stockbreeding Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, fibre, milk, or other products. It includes day-to-day care, management, production, nutrition, selective breeding, and the raising of livestock. ...

and farming were the principal economic activities in Talabre. Chile Route 23 passes about west of Lascar. Lascar, like

El Tatio El Tatio is a geothermal field with many geysers located in the Andes Mountains of northern Chile at above mean sea level. It is the third-largest geyser field in the world and the largest in the Southern Hemisphere. Various meanings have bee ...

, is a destination for volcano

tourism Tourism is travel for pleasure, and the Commerce, commercial activity of providing and supporting such travel. World Tourism Organization, UN Tourism defines tourism more generally, in terms which go "beyond the common perception of tourism as ...

. Unlike the neighbouring volcanoes

Acamarachi __NOTOC__ Acamarachi (also known as ''Pili'') is a high volcano in northern Chile. In this part of Chile, it is the highest volcano. Its name means "black moon". It is a volcano in the Central Volcanic Zone of the Andes, a zone of strong volcan ...

Licancabur Licancabur () is a prominent, stratovolcano on the Bolivia–Chile border in the Central Volcanic Zone of the Andes. It is capped by a wide summit crater which contains Licancabur Lake, a Volcanic crater lake, crater lake that is among the hig ...

and Quimal, there is no evidence of archeological sites on Lascar, possibly because of the volcanic activity. However, the inhabitants of the town of Camar consider Lascar a protective mountain spirit and in Susques (

) it is believed that

snow Snow consists of 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 througho ...

will fall if Lascar is steaming strongly. The inhabitants of Talabre give the volcano gifts, viewing it as their source of water.

Geography and geological context

Regional setting

Volcanoes in the Andes occur in four separate regions: the

Northern Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca plate and Antarctic plate underneath the South America ...

between 2°N and 5°S, the

between 16°S and 28°S, the

Southern Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca plate and Antarctic plate underneath the South America ...

between 33°S and 46°S, and the

Austral Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca plate and Antarctic plate underneath the South Americ ...

, south of the Southern Volcanic Zone. These volcanic zones are separated by areas where recent

volcanism Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a he ...

is absent; one common theory is that the

processes responsible for volcanism form a subducting plate that is too shallow to trigger the formation of

. This shallow subduction appears to be triggered by the

Nazca Ridge The Nazca Ridge is a submarine ridge, located on the Nazca plate off the west coast of South America. This plate and ridge are currently subducting under the South American plate at a convergent boundary known as the Peru-Chile Trench at approxi ...

and the Juan Fernandez Ridge; the areas where they subduct beneath the Peru-Chile Trench coincide with the limits of the Central Volcanic Zone. It is possible that when these ridges are subducted, the

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

they carry disrupts the subduction process and reduces the supply of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

, which is important for the formation of melts. Of these volcanic zones, the Central Volcanic Zone of which Lascar is a member of is the largest, covering parts of

and

. The Central Volcanic Zone is located between two areas where subduction is shallower and volcanic activity is absent. In the Central Volcanic Zone, volcanism has been active for 120 million years, although it has undergone eastward migration during this time. Water released from the subducting plate triggers the formation of

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...

magmas that are then injected into the crust. About 122 volcanoes with

eruptions exist in the

Andean Volcanic Belt The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca plate and Antarctic plate underneath the South Americ ...

, including

Ojos del Salado Nevado Ojos del Salado is a Dormant volcano, 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 overlapp ...

which with a height of is the highest volcano in the world. Many of these volcanoes are covered by

and

ice Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...

. A number of

supervolcano A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than . Supervolcanoes occur whe ...

es exist in the Central Volcanic Zone, they are part of the Altiplano-Puna volcanic complex.

Local setting

The volcanism of Lascar relates to the subduction of the

beneath the

. The Central Andes contain many hundreds of volcanoes, extending over the countries of Argentina, Bolivia, Chile and Peru. In this remote territory, where eruptions are poorly recorded, many volcanoes are higher than . They are constructed on a crust that is between thick. Volcanic centres include

s and associated large

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 surrou ...

lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...

s and

stratovolcanoes A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a ...

; among the better-researched volcanoes are Galan, Nevados de Payachata, Ollague, Purico Complex, San Pedro– San Pablo,

Tata Sabaya Tata Sabaya is a high volcano in Bolivia. It is part of the Central Volcanic Zone, one of several volcanic belts in the Andes which are separated by gaps without volcanic activity. This section of the Andes was volcanically active since the J ...

and Tumisa. Over 44 volcanoes in the region are considered potentially active, with a number of young volcanoes featuring

fumarolic A fumarole (or fumerole) is a vent in the surface of the Earth or another 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 ...

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

activity.

Guallatiri Guallatiri is a volcano in Chile with an elevation of . It is located southwest of the Nevados de Quimsachata volcanic group; some sources classify Guallatiri as a member. Guallatiri is a stratovolcano with numerous fumaroles around the summi ...

, for example, features fumarolic activity that is visible in satellite images. Also fumarolically active are:

Sabancaya Sabancaya is an active stratovolcano in the Andes of southern Peru, about northwest of Arequipa. It is considered part of the Central Volcanic Zone of the Andes, one of the three distinct volcanic belts of the Andes. The Central Volcanic Zone i ...

El Misti Misti is a dormant volcano located in the Andes mountains in southern Peru, rising above Peru's second-largest city, Arequipa. It is a conical volcano with two nested summit craters, the inner one of which contains a volcanic plug or lava dome ...

Ubinas Ubinas is an active stratovolcano in the Moquegua Region of southern Peru, approximately east of the city of Arequipa. Part of the Central Volcanic Zone of the Andes, it rises above sea level. The volcano's summit is cut by a and caldera, w ...

Tacora Tacora is a stratovolcano located in the Andes of the Arica y Parinacota Region of Chile. Near the border with Peru, it is one of the northernmost volcanoes of Chile. It is part of the Central Volcanic Zone in Chile, one of the four volcanic bel ...

Isluga Isluga () is a stratovolcano located in Colchane, west of the Chile-Bolivia border and at the west end of a group of volcanoes lined up in an east-west direction, which also includes the volcanoes Cabaray and Tata Sabaya. Isluga has an elongate ...

Irruputuncu Irruputuncu is a volcano in the commune of Pica, Tamarugal Province, Tarapacá Region, Chile, as well as San Pedro de Quemes Municipality, Nor Lípez Province, Potosí Department, Bolivia. The mountain's summit is high and has two summit c ...

Olca Olca is a stratovolcano on the border of Chile and Bolivia. It lies in the middle of a 15 km long ridge composed of several stratovolcanos. Cerro Minchincha lies to the west and Paruma to the east. It is also close to the pre-Holocene Cerro ...

, Ollague, San Pedro,

Putana In Hinduism, Pūtanā () is a Rakshasa, rakshasi (demoness), who was killed by the infant-god Krishna. Putana disguises as a young, beautiful woman and tries to kill the god by breast-feeding poisoned milk; however Krishna sucks her milk as well ...

and

Lastarria Lastarria is a high stratovolcano that lies on the border between Chile and Argentina. It is remote, and the surroundings are uninhabited but can be reached through an unpaved road. The volcano is part of the Central Volcanic Zone, one of the ...

. The largest historical eruption occurred at

Huaynaputina Huaynaputina ( ; ) is a volcano in a volcanic high plateau in southern Peru. Lying in the Central Volcanic Zone of the Andes, it was formed by the subduction of the oceanic Nazca Plate under the continental South American Plate. Huaynaputina ...

in 1600. Given the low population density around many of these volcanoes, there is often little information on their activity. Lascar is located in the

Antofagasta Region The Antofagasta Region (, ) is one of Chile's Administrative divisions of Chile, sixteen first-order administrative divisions. Being the second-largest region of Chile in area, it comprises three provinces, Antofagasta Province, Antofagasta, El ...

of Chile, and is , , or high, according to different sources. With a surface area of , the volcano has a volume of . Geographically, the area of Lascar is located between the Altiplano and the

Salar de Atacama Salar de Atacama, located south of San Pedro de Atacama, is the largest Salt pan (geology), salt flat in Chile. It is surrounded by mountains and lacks drainage outlets. To the east, it is enclosed by the main chain of the Andes, while to the wes ...

farther west; the terrain at Lascar dips in the direction of the Salar. Lascar is located in the main

, on the western margin of the

Altiplano The Altiplano (Spanish language, Spanish for "high plain"), Collao (Quechuan languages, Quechua and Aymara language, Aymara: Qullaw, meaning "place of the Qulla people, Qulla") or Andean Plateau, in west-central South America, is the most extens ...

. The

andesitic 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 predomina ...

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 rhyolite. ...

is located east of Lascar; it may have formed a

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

close to the summit during the Holocene. Aguas Calientes is older than Lascar, and it might share a

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 u ...

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 ...

–

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

volcanic centres in the neighbourhood include Cerro Negro in the north, Acamarachi northeast, Tumisa southwest, and the Cordon de Puntas Negras in the south, which Lascar is sometimes considered to be part of. Tumisa, to the south of Lascar, was active between 2.5 and 0.4 million years ago, is composed of

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. ...

and surrounded by

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 ...

deposits. East of Lascar lies the La Pacana caldera. Cerro Opla, west of Lascar, is a hill formed by

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

–

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, 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 coo ...

. An area of increased

electrical conductivity Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity in ...

has been identified beneath Lascar and extends to some neighbouring volcanoes, reaching a depth of over south of Lascar. The Quebrada de Chaile, the Quebrada de Soncor and the Quebrada de Talabre

canyon A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...

s run towards Salar de Atacama; they are deep and wide. These valleys were probably formed by erosion during glacial periods. The valleys drain the western, northern and southwestern slopes of Lascar. The southeastern slopes drain into

Laguna Lejía Laguna Lejía is a salt lake located in the Altiplano of the Antofagasta Region of northern Chile. The landscape of the area is dominated by the volcanoes Chiliques, Lascar, Aguas Calientes and Acamarachi. It is shallow and has no outlet, cov ...

which is close to the volcano, and the northwestern slope drains through the Quebrada de Morro Blanco. Lascar is located atop of a

ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

formed by the Cerro Corona and Cerro de Saltar lava domes, south and north of Lascar, respectively. Cerro Corona gets its name from a crown-shaped structure at its top. These domes cover a surface area of about . These lava domes are about 5 million years old, and are composed of dacite and smaller amounts of

pyroxene The pyroxenes (commonly abbreviated 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 ions of calcium (Ca), sodium (Na), iron ( ...

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 predomina ...

, along with

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

and visible minerals including

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

and

hornblende Hornblende is a complex silicate minerals#Inosilicates, 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 ...

. An eruption 16,700 years ago from Corona deposited

tephra Tephra is fragmental material produced by a Volcano, 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, ...

containing biotite and

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

in Laguna Lejía and generated a rhyodacitic lava flow. Another debris flow from Corona spread towards Salar de Atacama.

Geology

Lascar is a steep volcano formed by two irregularly shaped truncated cones that extend east–west, on a trend that includes Aguas Calientes. Six

s are located on the volcano, but sometimes only five craters are counted, in which case the central crater is considered to be the active one. The extinct western cone (also known as Apagado) is composed of layers of

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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

and pyroclastics. Its large crater is filled by another cone, which forms the highest summit of the Lascar volcano. Immediately east of it lies the eastern cone, which is contiguous with the western cone. The eastern cone (also known as Activo) is capped off with three distinct craters which are delimited by arcuate fractures. Measurements made from 1961 to 1997 determined that the eastern crater is wide and deep and thus the largest, the central crater is wide and deep, and the western crater is wide and deep, increasing to depth in 2005–2006. The craters show evidence that activity has migrated westward. The westernmost of these three eastern craters is the currently active one, surrounded by rims that reach heights of . In 1985, a hot spot in this crater was observed in satellite images. In the centre of the westernmost crater lies a smaller crater, with dimensions of and a depth of . There are furrows formed by erosion, large blocks, deposits of

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

and many

fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or another 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 along the rim of the inner crater. The exact configuration is variable owing to ongoing volcanic activity. The rims of the craters are partially buried by

s or cut by

rockslide A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses ''en masse'' and not in individual blocks. Note that a rockslide is similar to an ava ...

s. Layers of lava and pyroclastics are discernible in the craters. These craters are not collapsed calderas, and there is no evidence of the deposits a large explosion would produce. Remnants of a previous edifice are visible in the craters; this older edifice constitutes the bulk of the eastern cone. There are traces of a collapse of the volcano towards the northeast, with an associated horseshoe-shaped scar. Large lava flows are noticeable on the flanks of the volcano, with a total of eight lava flows recognized. They extend from the summit craters, although none of them appear to be associated with the currently active crater. Flows from the first stage of Lascar's activity are exposed at its western foot, while lava flows are buried beneath pyroclastic material on the eastern flank. A lava flow on the northern flank reaches almost to the village of Talabre. This lava flow is known as the Tumbres–Talabre lava flow; its margins are high, and it features a central channel. The flow advanced just north of the head of Quebrada Talabre before passing over cliffs and entering it. Another lava flow on the southwest flank is known as the Capricorn Lava. This dacitic lava was erupted on Lascar at high altitude and has a blocky surface. It features well developed levees and a flow front. Its rocks have a pale gray-blue colour, and their composition resembles the Soncor flow, despite more

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 include ...

lavas and pyroclastics being erupted in the time period between the emplacement of the Soncor flow and the Capricorn Lava. An early pyroclastic flow, the Saltar Flow, is exposed on the eastern flank. It was emplaced after the collapse of the oldest edifice, covering Aguas Calientes' western slopes. The flow deposit was later modified by

glacial A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

activity. The Soncor flow is found primarily on the western side of Lascar, with part of it also southeast of Lascar. On the western slope, it buries the even older Piedras Grandes flow, which crops out only at the margins of the Soncor flow. While the Piedras Grandes flow was formed by a

glacier run A glacial lake outburst flood (GLOF) is a type of outburst flood caused by the failure of a Proglacial lake, dam containing a glacial lake. An event similar to a GLOF, where a body of water contained by a glacier melts or overflows the glacier, ...

that transported blocks with sizes of up to , Soncor was formed by a large eruption. The large eruption gave rise to a pyroclastic flow that extended westward and contained

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

and various magmas. It was accompanied by a

Plinian Plinian eruptions or Vesuvian eruptions are volcanic eruptions characterized by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a le ...

fall deposit. Finally, the andesitic

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...

Tumbres flow is found on the northwest–west–southwestern slopes of Lascar. The Quebrada Talabre cuts into the upper flanks of Lascar and eventually joins the Quebrada Soncor.

Lahar A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are o ...

deposits are found in adjacent valleys, suggesting that wetter periods had occurred during Lascar's activity. The Quebrada Talabre was scoured by pyroclastic flows during the 1993 eruption, exposing bedrock and

Tertiary Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to: * Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago * Tertiary (chemistry), a term describing bonding patterns in organic ch ...

s. Traces of glacial action are found on the older parts of Lascar at altitudes above and include meltwater gorges, striated rock surfaces, and U-shaped valleys.

Moraine A moraine is any accumulation of unconsolidated debris (regolith and Rock (geology), rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a gla ...

s are found at Tumisa down to an altitude of . The volcano sits above a major local geological trend, the north–south Miscanti Line. Other volcanic centres are also located on this line, including the Corona and Saltar lava domes, and the Miscanti and Lejia volcanoes. The Miscanti Line dissects the

basement A basement is any Storey, floor of a building that is not above the grade plane. Especially in residential buildings, it often is used as a utility space for a building, where such items as the Furnace (house heating), furnace, water heating, ...

beneath Lascar, and it may be a hinge of a fold that is being propagated by faults. The formation of the first cone at Lascar may have been facilitated by the intersection between the Miscanti Line and another east–west

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-align ...

formed by

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

tectonic compression of the region, and the lineament would have worked as an ascent path for magma. At least four alignments of volcanoes are recognized in the region.

Composition

Lascar rocks consist of andesite and dacite. These rocks have a composition mainly characterized as "two-pyroxene", but the old Piedras Grandes and Soncor rocks contain hornblende. Other minerals include

anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...

augite Augite, also known as Augurite, is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid soluti ...

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

which is also the dominant

phenocryst image:montblanc granite phenocrysts.JPG, 300px, Granites often have large feldspar, feldspathic phenocrysts. This granite, from the Switzerland, Swiss side of the Mont Blanc massif, has large white phenocrysts of plagioclase (that have trapezoid sh ...

phase in Lascar rocks,

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

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, printi ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

orthopyroxene The pyroxenes (commonly abbreviated 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 ions of calcium (Ca), sodium (Na), iron (Fe( ...

phyrrotite Pyrrhotite ('' pyrrhos'' in Greek meaning "flame-coloured"'')'' is an iron sulfide mineral with the formula Fe(1−x)S (x = 0 to 0.125). It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnet ...

, quartz, rhyolite in the

groundmass The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded. The matrix of an igneous rock consists of finer-grained, often microscopic, crystals in which larger crystals, ...

, and

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Prop ...

in inclusions. Dacite has more plagioclase and rhyolite. Additional component minerals found at Lascar include

anorthite Anorthite (< ''an'' 'not' + ''ortho'' 'straight') is the

calcium

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull ...

bronzite Bronzite is a member of the pyroxene group of minerals, belonging with enstatite and hypersthene to the orthorhombic series of the group. Rather than a distinct species, it is really a ferriferous variety of enstatite, which owing to partial alt ...

fassaite Fassaite is a variety of augite with a very low iron content, . It is named after the Fassa Valley, Italy. It is thought to be a contact mineral formed at high temperature on the interface between volcanic rocks and limestone. It is also reporte ...

forsterite Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich Endmember, end-member of the olivine solid solution series. It is Isomorphism (crystallography), isomorphous with the iron-rich end-member, fayalit ...

hypersthene Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Its chemical formula is . It is found in igneous and some metamorphic rocks as well as in stony and iron meteorites. Many references have f ...

pigeonite Pigeonite is a mineral in the clinopyroxene subgroup of the pyroxene group. It has a general formula of . The calcium cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations. Pigeonite crystallizes in ...

and more. The rocks of Lascar 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 ...

series. concentrations range from 55.5 to 67.8% by weight, and the rocks have medium to large concentrations of

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

. The magmas are contaminated by the local crust, but not to the extent found in the Galan or Purico complex eruption products. The magma interacts with former salar deposits before ascending. The chemistry of Lascar's rocks is fairly similar to those of neighbouring Tumisa volcano. Magma erupted by Lascar appears to form from the mixing of mafic and more evolved magmas; the 1993 eruption deposits contain bands of different rocks. Specifically,

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...

magma is periodically injected into a

, where crystal fractionation and mixing processes take place, with their relative contributions varying depending on magma resupply rates. The average magma resupply rate is high, thus the magmas are relatively unevolved; presumably, if the supply of mafic magma is steady, the products are andesitic, otherwise dacite forms. This origin of Lascar magmas is reflected in the textures of rocks.

Petrologic Petrology () is the branch of geology that studies rock (geology), rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous petrology, igneous, metamorphic rock, ...

investigations indicate that at least three components give rise to Lascar's magmas, an upper crustal one, a mantle component and an enriched component that may come either from the lower crust or the downgoing

slab Slab or SLAB may refer to: Physical materials * Concrete slab, a flat concrete plate used in construction * Stone slab, a flat stone used in construction * Slab (casting), a length of metal * Slab (geology), that portion of a tectonic plate that ...

. The overall magma supply rate of Lascar is . The magma chamber of Lascar appears to lie at depths of , although the lack of deformation of the edifice during the 1993 eruption indicates that it may be deeper, over or even over deep. Magma

petrology Petrology () is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous ...

implies that there is another reservoir at depth. A large regional-scale structure, the

Altiplano-Puna Magma Body The Altiplano-Puna Magma Body (APMB), a magma body located within the Altiplano-Puna plateau approximately 10–20 km beneath the Altiplano-Puna Volcanic Complex (APVC) in the Central Andes. High resolution tomography shows that this magma b ...

, underlies Lascar. There appear to be two distinct chamber systems, an andesitic one that is responsible for the frequent andesite lava and

activity, and a dacitic one that was involved in the Piedras Grandes and Soncor activities. Temperatures of the magma chamber range from ; the mafic magmas that are injected in the chamber are about hotter than the extant andesite and dacite. The chamber may be surrounded by

skarn Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, ...

ic alteration. This alteration gives rise to

wollastonite Wollastonite is a calcium Silicate minerals, inosilicate mineral (calcium, Casilicon, Sioxygen, O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or D ...

and

-containing skarn, depending on the distance from the magma chamber walls.

Metasomatism 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 traditionally defined as metamorphism which involves a change in the chemical com ...

does further affect rocks derived from magma chamber walls. The conditions at the magma chamber may be comparable to these under which

epithermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

mineral deposits form. The

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

conditions in the magma chamber are favourable for the formation of

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

, but unfavourable for the deposition of

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

minerals. A number of

xenolith A xenolith ("foreign rock") is a rock (geology), rock fragment (Country rock (geology), country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusi ...

s occur in Lascar's rocks; a large amount of the

s are ultimately derived from them.

Hornfels Hornfels is the group name for a set of Metamorphism#Contact .28thermal.29, contact metamorphic rocks that have been baked and hardened by the heat of Intrusive rock, intrusive igneous masses and have been rendered massive, hard, splintery, and in ...

, skarn, and rocks that are part of Lascar's lava dome ridge are the source of these xenoliths. Minerals encountered in xenoliths include

andradite Andradite is a Mineralogy, mineral species of the Garnet, garnet group. It is a Silicate minerals#Nesosilicates, nesosilicate, with chemical formula Ca3Fe2Si3O12. Andradite includes three varieties: * ''Colophonite'': a historical variety found ...

, anhydrite, anorthite, apatite, biotite,

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

, diopside, fassaite,

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

, ilmenite, magnetite,

monazite Monazite is a primarily reddish-brown phosphate mineral that contains rare-earth elements. Due to variability in composition, monazite is considered a group of minerals. The most common species of the group is monazite-(Ce), that is, the cerium ...

, orthopyroxene,

perovskite Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as , known as the perovskite (stru ...

, plagioclase,

prehnite Prehnite is an inosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2 with limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most often forms as stalactitic ...

, quartz,

sphene Titanite, or sphene (), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium; calcium may be partly rep ...

thorite Thorite, (Th,U)SiO4, is a rare nesosilicate of thorium that crystallizes in the tetragonal system and is isomorphous with zircon and hafnon. It is the most common mineral of thorium and is nearly always strongly radioactive. Thorite was discover ...

, wilkeite, wollastonite and

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

. A number of such xenoliths formed from

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

rocks that were influenced by magma of Lascar and of other volcanoes such as Tumisa.

Gas emissions

Lascar emits plumes of gas and white clouds of condensed

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

, mostly through many hundreds of

vents, which are chiefly located in the active crater. The temperatures range between ; in December 2002, two fumaroles had temperatures exceeding . Total flux is estimated to be , and occurs even between eruptions. The vents are active for years. Their positions in the crater is influenced by ring-shaped fractures in the crater floor. There are high-temperature fumaroles (temperatures equal to or exceeding ) and low-temperature fumaroles (temperatures of less than ), with noticeable chemical differences between the two; the latter tend to emit far more

than

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

. The fumaroles also release

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

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

, and smaller amounts of

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

Hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s and other organic compounds are also found in the low-temperature fumaroles. Trace elements include

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

boron Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...

and

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

, with smaller amounts of

barium Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

copper Copper is a chemical element; it has symbol Cu (from Latin ) 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 pinkish-orang ...

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...

and

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

. The fumarole gases react with surrounding rocks, forming precipitates and altered rocks. Lascar is an important source of chalcophile elements in northern Chile. Release rates of amounted to in 1989, and in 2003. Overall sulfur output ranges between . This corresponds to about 1% of global volcanic sulfur emissions, and is comparable to Kilauea and Villarica. Lascar was a substantial source of

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...

for the atmosphere around 30° south, reaching a proportion of 20–40% the sulfur over South America and still 10–20% over the South

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

. In 2005, Lascar was the third-largest source of volcanic

in the world among continuously active volcanoes, behind Etna in

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

and

Bagana Bagana is an active volcanic cone located in the centre of the island of Bougainville Island, Bougainville, Papua New Guinea, the largest island of the Solomon Islands (archipelago), Solomon group. It is the most active volcano in the country, ...

Papua-New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

. Since 2014, however, the Peruvian volcanoes

and

have become the largest source of

tropospheric The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the planetary s ...

sulfur dioxide from the Central Volcanic Zone. There are temporal variations in the output: after a decrease in 2009, sulfur output increased in 2012, probably as a consequence of the arrival of new

at depth. There is no clear association between periods of degassing and eruptions. Sulfur is released from areas all over the cone, resulting in a noticeable sulfur smell.

Hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

and

hydrogen fluoride Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...

are also released in large amounts, with estimates made in 2003–2004 indicating a mass flux of and respectively. They correspond to about 2 and 5%, respectively, of the global volcanic flux of these compounds. Finally, Lascar is vigorous producer of

dust particles, which are released at a rate of about 100,000 trillion particles per second. Gases are partly supplied from shallow magma; the volume of magma erupted is too small to contain all the exhalations. The release of gas by the magma is favoured by strong temperature contrasts between incoming magma and the magma chamber, and processes occurring during the mixing may explain the high emission of

by Lascar. The presence of

argon Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...

and

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

in low-temperature fumaroles indicates that air is involved in their formation, although a portion of each of these two gases is non-atmospheric.

Sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

and

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

may be derived from the crust,

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oce ...

s such as these found at

subducted Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plat ...

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...

or the mantle.

Carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

in the gases may come from

assimilation.

isotope data support the notion that evaporite deposits contribute part of Lascar's sulfur. Water appears to be in part magmatic and in part precipitation-derived. The high concentrations of

halogen The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...

s are typical for subduction-associated volcanoes; the halogens are supplied to the volcanoes through

-induced processes that act on the crust and the subducting plate. The heat output of Lascar is about during regular activity, but has been estimated to be as high as .

Electrical conductivity Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity in ...

data suggest that a hydrothermal system exists beneath Lascar, but the existence of such a system has been questioned.

Basement

Lascar rests atop the Atana ignimbrite, a rhyodacitic sheet which was erupted by La Pacana caldera 4.5–3.7 million years ago. The Pampa Chamaca and Tuyajto ignimbrites are somewhat younger, 2.6–2.2 million and less than 1 million years respectively. These ignimbrites form a 3° steep slope in the area. Other basement rocks are the

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

-containing marine

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

–

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

Lila

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

, the red-orange Permian Cas formation containing volcanic rocks and granites, as well as the volcanic Permian–Triassic Peine formation and Cerro Negro strata, which also contain

intruded Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March 27 ...

rocks and lake sediments. These formations are not visible in the Lascar area, but they crop out close to the

. Tertiary sediment and volcanic rocks can also be found. The presence of

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

is indicated by xenoliths in Lascar's lavas; the only place they crop out farther east is in Argentina. This limestone formation has been identified as the Yacoraite formation. Later deposits include the

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

sedimentary Quepe strata.

Landform A landform is a land feature on the solid surface of the Earth or other planetary body. They may be natural or may be anthropogenic (caused or influenced by human activity). Landforms together make up a given terrain, and their arrangement ...

s over this basement include ignimbrites, lava domes, and stratovolcanoes. Exposures of the basement are often delimited by faults.

Eruptive history

Lascar is one of the three most active volcanoes in the Andean Central Volcanic Zone (the other two are the Peruvian volcanoes

and

) and a steady pattern of eruptive activity has persisted for centuries. The volcano persistently features a tall plume of water and sulfur dioxide. Most present-day activity consists of the release of fumarolic gas with additional vulcanian activity that generates eruption columns several kilometres high, typically every three or two years and half of the time during austral spring as well as active deformation of the three active craters observed in

interferometric synthetic-aperture radar Interferometric synthetic aperture radar, abbreviated InSAR (or deprecated IfSAR), is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar (SAR) radar imaging, images to generate maps ...

. The long-term magma supply rate of Lascar is about , the volcano has produced about of rock.

Early activity

The oldest volcanic activity at Lascar occurred between 220,000 and less than 50,000 years ago. Activity has alternated between the eastern and western part of the volcano during its history. The eastern edifice formed first (stage I), erupting andesite containing pyroxene, and eventually forming the Chaile and Saltar pyroclastic flows. The oldest mafic andesites are less than 43,000 years old, while the Chaile and Saltar pyroclastic flows erupted over 26,500 years ago. An alternative dating scheme considers Chaile to be 47,000 ± 16,000 years old and Saltar 167,000 ± 9,000 years old. Lava flows less than thick issued from the stage I cone and reached lengths of . They occur beneath altitudes of , their vents buried by later activity. The lavas from stage I are mostly exposed north and west of Lascar. The Chaile flows are actually formed by two separate units and are found on the southwest flanks of the volcano, up to a distance of . They reach thicknesses of in the upper unit and in the lower one. The Saltar flow reached widths of and thicknesses of , increasing to where the flow entered valleys. At least nine units form the Saltar deposit, with the northern flows displaying flow welding. These deposits have volumes of and probably formed when an explosive eruption took place in a

lava lake Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified (sometim ...

. After the end of stage I, a period of glacial erosion occurred prior to new activity, which created furrows in the Saltar flow. Imprecise

argon–argon dating Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede Potassium-argon dating, potassiumargon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measur ...

on younger andesites has yielded dates of 14,000 ± 18,000 and 17,000 ± 22,000 years. Later volcanic activity buried this edifice beneath thin pyroclastic flows. The western edifice generated a complex of lava domes (stage II), which was probably surrounded by a horseshoe-shaped crater open to the west. Possibly, the magma chamber of stage I had almost solidified when the injection of basaltic magma at depths of over triggered a remelting. Andesite-

rhyodacite Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid ...

intrusions occurred beneath the volcano, some of which were still hot when the Soncor eruption tore them out of the ground. An

ice cap In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description By definition, ice caps are not constrained by topogra ...

formed over Lascar at that time, feeding two glaciers that extended northeast and southeast away from the volcano.

Piedras Grandes unit

The stage II activity was accompanied by the eruption of

block and ash flow A block and ash flow or block-and-ash flow is a flowing mixture of volcanic ash and large (>26 cm) angular blocks commonly formed as a result of a gravitational collapse of a lava dome or lava flow. Block and ash flows are a type of pyroclastic fl ...

s consisting of andesite, and an eruption whose deposits include blocks with sizes of . This unit, formed during stage II, is known as Piedras Grandes,and is exposed on the western slopes below about altitude. The unit is about wide and consists of large blocks encased in ash. The composition of the Piedras Grandes unit is andesite containing

amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

, basaltic andesite and hornblende. The Piedras Grandes unit is over 26,500 years old, possibly between 63,000 and 100,000 years old. Temperatures have been estimated to be for the andesite and for the basaltic andesite. The magmas were formed from a remelted proto-

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

that had been heated and resupplied with volatiles by mafic magmas. The lava domes interacted with

glaciers A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

, resulting in the formation of a glacier run whose deposits are found as far as from the volcano. Blocks with sizes of up to were transported by this flow. An alternative theory posits that the Piedras Grandes unit formed when an ice cap on Lascar interacted with a block and ash flow erupted by Aguas Calientes.

Soncor eruption

A major Plinian eruption occurred 26,450 ± 500 years ago, releasing of ejecta, both

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...

and pyroclastic flows. The deposits left contain both andesite and dacite, with phenocrysts consisting of apatite, augite, biotite,

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

titanium oxide Titanium oxide may refer to: * Titanium dioxide (titanium(IV) oxide), TiO2 * Titanium(II) oxide (titanium monoxide), TiO, a non-stoichiometric oxide * Titanium(III) oxide (dititanium trioxide), Ti2O3 * Ti3O * Ti2O * δ-TiOx (x= 0.68–0.75) * Ti ...

s, orthopyroxene and plagioclase in a rhyolite

matrix Matrix (: matrices or matrixes) or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the m ...

. The Plinian deposit has a colour ranging from white to creamy. Like the Piedras Grandes rocks, they tend towards high potassium quantities, and resemble other volcanic rocks of Lascar and the Central Andes in composition. The deposits are formed by a

fallout deposit and an ignimbrite rich in

lithics Lithic may refer to: *Relating to stone tools ** Lithic analysis, the analysis of stone tools and other chipped stone artifacts ** Lithic core, the part of a stone which has had flakes removed from it ** Lithic flake, the portion of a rock removed ...

. This Plinian deposit reaches thicknesses of and fell from a eruption column. The Soncor ignimbrite extended as much as west from the volcano, north and south. It is white, heterogeneous and mostly featureless with only weak sorting, but features a noticeable compositional zonation. The ignimbrite features three

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

, one rich in breccia, another rich in pumice, and a normal ignimbrite. Ignimbrite was channeled to the Salar de Atacama by the Quebrada de Chaile, Quebrada de Soncor and Quebrada de Talabre canyons and some smaller valleys, northeastwards by the Quebrada de Morro Blanco and as far as southeastwards over the Pampa Leija area. In these valleys, the ignimbrite can be as much as thick. Pumices are encased in the ignimbrite as lenses and levees and are also found in the terrain above the canyons. Estimated temperatures decreased from at the vent to farther down the flows. At the time of emplacement, the ignimbrite was still . Magma temperatures have been estimated at . The Soncor fallout deposit contains a basal gravelly layer and several layers of

and dacitic pumice which also contain lithics. The total volume of the Soncor eruption products has been estimated to be either

dense rock equivalent Dense-rock equivalent (DRE) is a volcanologic calculation used to estimate volcanic eruption volume. One of the widely accepted measures of the size of a historic or prehistoric eruption is the volume of magma ejected as pumice and volcanic ash, k ...

or net volume, both minimum estimates. Lithic rocks derived both from the pre-Soncor volcano and the basement are also represented. The magma erupted was generated in a magma chamber starting from andesite, which underwent complex petrogenetic processes. This magma chamber was located at a floor depth of (older estimate ) and probably had a complex shape, given certain chemical properties of the Soncor rocks. At the time preceding the eruption, the magma chamber had a thermal stratification; injections of mafic magmas had heated the magma chamber and induced

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

. A volatile phase containing chlorine formed inside the magma chamber and quickly removed most sulfur from the magma. This sulfur extraction was facilitated by the high

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

content of the magma, which allowed the formation of sulfur dioxide. Water is a principal volatile involved in the processes of

Plinian eruption Plinian eruptions or Vesuvian eruptions are volcanic eruptions characterized by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a le ...

s; the water content of the Soncor and Piedras Grandes magmas was about 4–5%. The Soncor magmas were associated with a volatile phase that underwent extensive interaction with the future eruption products. The previous volcanic edifice was destroyed by this eruption, which may have formed a caldera. The vent was no wider than , as it is completely hidden beneath the western cone. Such a vent or caldera is substantially smaller than the volume of rocks erupted, a discrepancy that is also evident in the 1932 eruption of Quizapu. The Soncor magma chamber may have been too deep to collapse when it was emptied, explaining why no significant caldera was formed. The Soncor deposit was subsequently affected 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 the stage I edifice by a

debris avalanche Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...

, which was radiocarbon dated at 22,310 +2,700/−2000 years ago in the Quebrada de Chaile. This debris avalanche is thick and long. The Capricorn Lava overlies the Soncor deposits.

Post-Soncor activity

Later, a new

grew over the Soncor vent. This volcano was formed by andesite-dacite lava flows (stage III) and

scoria Scoria or cinder is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackso ...

. Lava flows from this stage have thicknesses of and lengths reaching . It has a volume of . The growth of this volcano was preceded by a period of erosion between 20,800–20,100 and 12,500 years ago, coincident with the

Lake Minchin Lake Tauca is a former lake in the Altiplano of Bolivia. It is also known as Lake Pocoyu for its constituent lakes: Lake Poopó, Salar de Coipasa and Salar de Uyuni. The lake covered large parts of the southern Altiplano between the Eastern Co ...

humid period. Glaciers in the region reached their maximum size at that time. The deposits left by this erosional period contain no clear evidence of stage III activity; indeed Lascar was probably inactive between 14,000 and 10,500 years ago. However, an eruption of the Cerro Corona lava dome occurred during this period, and activity of stage III did not commence earlier than 22,300 years ago. The Tumbres eruption occurred around 7250

, commencing with the eruption of pumice falls that reach thicknesses of less than . Afterwards, up to four different units of pyroclastic flows, each thick, formed deposits up to long. At the end of the eruption, a caldera and the two western craters formed. The deposits left by this eruption contain basaltic andesite-andesite and were subject to agglutination and welding. Originally considered part of stage III, it was more recently attributed to stage IV given the considerable (6,000 years) temporal gap between the Tumbres eruption and stage III volcanism, and the geochemistry of the rocks. The Manquez

agglutinate In linguistics, agglutination is a morphological process in which words are formed by stringing together morphemes (word parts), each of which corresponds to a single syntactic feature. Languages that use agglutination widely are called agglut ...

above the Tumbres deposits was formed either by the Tumbres eruption or by a subsequent stage; a

pyroclastic cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

in the western crater may be associated with this agglutinate. Activity subsequently shifted to the eastern edifice. Around 5150 ± 1250 BCE, as obtained by

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 hist ...

, the Tumbres-Talabre lava flow was erupted from the eastern crater. This flow extends northwest and is thick. The Tumbres-Talabre flow was originally considered to be of late-19th-century age. It probably formed when one of the craters filled with andesitic lava to the point of overflow. This eruption was the last

effusive eruption An effusive eruption is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground. Overview There are two major groupings of eruptions: effusive and explosive. Effusive eruption differs from explosive eruption ...

of Lascar, when later lava domes are excluded. The three eastern summit craters formed at the time when the Tumbres-Talabre flow erupted in the remains of the stage I cone. This edifice is the currently active one, with the deepest of its three summit craters being active.

Historical activity

Lascar has erupted about thirty times since the 19th century. Written reports of volcanic activity exist since the 16th century, when the

Spaniard Spaniards, or Spanish people, are a Romance languages, Romance-speaking Ethnicity, ethnic group native to the Iberian Peninsula, primarily associated with the modern Nation state, nation-state of Spain. Genetics, Genetically and Ethnolinguisti ...

s arrived in the region, though few records exist from before 1848. Volcanic activity recorded after 1848 consists chiefly of fumarolic emissions and occasional explosive activity. Recorded eruptions occurred in 1858, 1875, 1883–1885, 1898–1900(?) and 1902, ranging from a

volcanic explosivity index The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by Christopher G. Newhall of the United States Geological Survey and Stephen Self in 1982. Volume of products, eruption c ...

(VEI) of 0 to VEI 2. The 1933 eruption was seen as far away as

Chuquicamata Chuquicamata ( ; referred to as Chuqui for short) is the largest open-pit mining, open pit copper Mining, mine in terms of excavated volume in the world. It is located in the north of Chile, just outside Calama, Chile, Calama, at above sea level. ...

. Another series of eruptions occurred between November 1951 and January 1952; one eruption is recorded from 1940. Eruptions were observed in March 1960, which were accompanied by earthquakes felt in Toconao, as well as in September 1964 when ash fell in Socaire. Yet another eruption sequence occurred between 1959 and 1969. Eruptions in 1972 and 1974 are uncertain. For some eruptions, including the January 1854 eruption, it is not clear whether they occurred at Lascar or Aguas Calientes, and some early reports of volcanic activity at Aguas Calientes probably refer to Lascar. In 1984, Lascar awakened to new activity;

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

images noted the presence of hot spots on the volcano.

Landsat The Landsat program is the longest-running enterprise for acquisition of satellite imagery of Earth. It is a joint NASA / USGS program. On 23 July 1972, the Earth Resources Technology Satellite was launched. This was eventually renamed to Lan ...

images taken during this time indicate that a lava lake may have existed in the central crater, generating a plume of volcanic gases and, in September 1986, a vulcanian eruption happened and dropped ash in

Salta, Argentina Salta () is the capital and largest city in the Argentine province of the same name. With a population of 618,375 according to the 2010 census, it is also the 7th most-populous city in Argentina. The city serves as the cultural and economic c ...

. This eruption was first noticed when ash fell on Salta, and was accompanied by anomalies in the heat emission from the volcano recorded by satellite. The eruption was also observed by geologists in Toconao, where the explosion was violent enough to wake up people who were sleeping. Observers noted the formation of a cauliflower-shaped cloud that eventually developed into a

mushroom cloud A mushroom cloud is a distinctive mushroom-shaped flammagenitus cloud of debris, smoke, and usually condensed water vapour resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently e ...

with a maximum height of above the volcano. The eruption itself lasted only about five minutes and consisted of two pulses. Ash fall in Salta occurred about one hour after the eruption. This eruption was the most significant of the previous two decades, having a VEI of 3. Preceding historical eruptions did not exceed 2. A and lava dome formed in early 1989. This dome began to shrink in October 1989, and in December 1989, white clouds rose above Lascar's crater. On 20 February 1990, an eruption column rose above the crater, resulting in ash fall over away from the volcano. In March 1990, the lava dome had a temperature of , with some parts exceeding .

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 viscosity, viscous fragments of lava during an eruption. Because volcanic bombs cool a ...

s with diameters of up to were hurled as far as from the crater, presumably as a consequence of the lava dome exploding. Some of the material came from the conduit walls. The lava dome had disappeared, but in early 1992, another lava dome formed, eventually reaching a size of width and height, and was accompanied by explosions. It probably started shrinking in April 1992, although the shrinkage was directly visible only in November. Small explosions accompanied the shrinkage until, by March 1993, the dome had disappeared again. An alternating cycle of fumarolic activity, an accumulation of fumarolic gases in the conduit and lava dome, and explosive activity followed by renewed fumarolic activity have characterized Lascar's activity since 1984. Explosive activity presumably occurs when gases can no longer escape. This occurs because as the magma loses its gas content, the number of pores in it, and thus its permeability to gas, decreases. Further, fractures permitting gas passage are obstructed when the magma contracts. Most of the time, numerous fumaroles within the crater form a plume that reaches an altitude of . During minor explosive eruptions, eruption columns reach heights of up to . The temperatures of the lava dome can reach . This cycle ended after 1993, probably because the April 1993 eruption modified the conditions in the volcanic system. Alternatively, the cycle may have continued, to reach another lava dome collapse stage in early 2003. While eruptions before 1993 had always been preceded by a reduction in heat radiated from the volcano, such a reduction in 1999–2000 did not lead to an eruption, and when an eruption took place in July 2000, it was preceded by only a brief drop in heat radiation.

1993 eruption

Vulcanian explosions started on 18 April 1993, and on 19–20 April 1993, a major eruption occurred. A

phreatic eruption A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evap ...

around 14:30 on 18 April formed the prelude to the eruption. The eruption commenced with two explosions at 6:28 and 9:20 local time, forming eruption columns high. Another explosion at 13:02 sent a column high. At least ten different pulses were observed, generating columns of various heights and forming mushroom clouds. The strongest pulse occurred on 20 April between 6:28 and 9:20 and sent flows towards the northwest. This pulse generated an eruption column high. The total mass flux of the eruption was about , comparable to the 1982 eruption of El Chichon. The lava dome in the crater was destroyed and was probably the source of the lava bombs that were thrown as far as away from the vent; some of these bombs had diameters of and left large

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

s. The eruption columns underwent several collapses, creating pyroclastic flows at least seven to nine times. The first pyroclastic flow was observed around 10:12 on 19 April. Other flows occurred at 12:05, after 13:37, 17:25, 21:35–21:48, 23:40–23:50 and on 20 April at 9:20. After being discharged through gaps in the crater rim, pyroclastic flows on the northwestern and the eastern sides reached lengths of , and on the southern side. These flows reached a thickness of about and advanced through the Quebrada de Talabre, which had intercepted the flows on the northern flank. On the southeastern flank, the pyroclastic flows formed a fan extending several hundred metres into Pampa Leija. Pyroclastic flows reached a speed of , and themselves generated ash surges that partly rose above the flows. Hot pyroclastic flows on the southeastern flank covered a surface area of . The southern flank flows at first proceeded along a gully before spreading out. The total area covered by the flows is about on the northern slopes (Tumbres fan) and on the southern slopes (Lejia fan). The flows left lobate structures that form a stacked deposit, which shows such structures as levees and finger-like toes. The speed of these flows has been estimated at . About 30% of these flows were formed by ash and 70% by blocks, with larger fragments accumulating on the margins of each flow deposit. The pyroclastic flow deposits contain lithics from several sources, as well as pumice. Pumice mostly accumulated on the surface of the flows, and individual stones are up to wide. Lithic blocks are up to thick. The total volume of these pyroclastic flows is about . There is a pronounced morphology characterized by a channel upslope and snout-like toes downslope. Flow surfaces display pronounced fractures with a V profile, which developed a year after the eruption. The pyroclastic flow surfaces subsided after the eruption, with pulses of faster subsidence coinciding with the 1995 Antofagasta earthquake and the

2007 Tocopilla earthquake The 2007 Tocopilla earthquake occurred on November 14 at . Its epicenter was located between Quillagua and Tocopilla, affecting the Tarapacá and the Antofagasta regions in northern Chile. The earthquake had a moment magnitude of 7.7 and lasted ...

. The flows were strongly erosive, extracting rocks and material from the bedrock, even far away from the vent. Noticeable

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

occurred in the areas over which pyroclastic flows had passed, forming abrasion surfaces and removing loose

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

from the ground. These flows took a long time to cool down; in the Quebrada Tumbres, they had not cooled down completely by December 1993. Additional surfaces were covered by ash cloud surges, reaching thicknesses of no more than on the sides of the pyroclastic flows. In some parts of the edifice, ejecta formed layers thick enough to undergo landsliding. The deposits and small structures, such as levees and lobes, were conserved by the dry climate in the region. The ash from the volcano was carried by western wind towards Argentina and the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. Ash fall in Tucuman and

Santiago del Estero Santiago del Estero (, Spanish for ''Saint-James-Upon-The-Lagoon'') is the capital of Santiago del Estero Province in northern Argentina. It has a population of 252,192 inhabitants, () making it the twelfth largest city in the country, with a sur ...

was intense enough that traffic ground to a halt, and

air travel Air travel is a form of travel in vehicles such as airplanes, jet aircraft, helicopters, hot air balloons, blimps, Glider (aircraft), gliders, Hang gliding, hang gliders, parachuting, parachutes, or anything else that can sustain flight.

was impacted internationally. Authorities closed schools in Argentine provinces close to the volcano and recommended that people not go out without masks.

Tephra Tephra is fragmental material produced by a Volcano, 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, ...

fall from this eruption was recorded in Argentina, including in

, away, and in Brazil, Paraguay, and Uruguay. Ash from this eruption was identified in

ice core An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier ...

s from

Illimani Illimani () is the highest mountain in the Cordillera Real (part of the Cordillera Oriental, a subrange of the Andes) of western Bolivia. It lies near the cities of El Alto and La Paz at the eastern edge of the Altiplano. It is the second high ...

while

s reportedly appeared in ice taken from the

Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...

and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

. Over of ash fell over a surface area of over . Larger particles fell closer to the volcano, while smaller particles were carried farther. Volcanic ash deposited close to the volcano was partially remobilized by winds a few days after the eruption. This eruption was the most significant eruption of Lascar in the last 9,000 years, with a volcanic explosivity index of 4 and a duration of 32 hours, and one of the most significant volcanic eruptions in the recent history of Chile. It caused noticeable changes in the morphology of the volcano, including the formation of a new fracture along the summit craters; however, the summit craters themselves were not heavily altered apart from the formation of a trench across the three craters that runs in west–east direction. The whole volcano did not deform during the eruption sequence. The eruption released about of sulfur dioxide, about half the quantity released by the

1980 eruption of Mount St. Helens In March 1980, a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of Phreatic eruption, phreatic blasts occurred from the summit and escalated until a major ...

, and was sufficient to cause a noticeable increase in atmospheric

opacity Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shie ...

. The Quebrada Tumbre was blocked, and its water chemistry noticeably altered, by the eruption. About of gypsum was deposited in the drainages around the volcano, forming a significant supply of sulfur in the region. The people of Talabre were evacuated during the eruption to Toconao, although some ignored evacuation orders. There were no injuries or fatalities, however the eruption did lead to

water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...

in the region, including increases in

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

, copper and lead concentrations in local rivers. An increase of mercury from the eruption was detected as far as Laguna del Plata, Argentina. The 1993 eruption was followed by a significant increase in the

fluorine Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...

content of plants covered by the ash. Regulatory limits on concentrations of other elements in water were also exceeded, although only temporarily.

Post-1993 activity

The eruption record at Lascar becomes more irregular after the 1993 eruption. During April 1993, a new lava dome formed in the crater. It was larger than preceding lava domes, reaching a diameter of . It started to shrink again by May. On 17 December 1993, another explosion created an eruption column high. By 28 December, the dome had subsided completely in the centre, leaving only its margins. Subsequently, a number of fumaroles were active around the crater. Explosive eruptions, accompanied by the formation of eruption columns reaching heights of several kilometres, sometimes leading to ash fall in

Jujuy, Argentina San Salvador de Jujuy (), commonly known as Jujuy and locally often referred to as San Salvador, is the capital and largest city of Jujuy Province in northwest Argentina. Also, it is the seat of the Doctor Manuel Belgrano Department. It lies near ...

, occurred on 27 February 1994; in July 1994, November 1994, and March 1995; and on 10 May, 20 July and 18 October 1996. During the July 1995 eruption, subsidence was noted on satellite images of the inside of the central crater. The collapse structures during this activity were larger than those noted in previous activity, possibly because the April 1993 eruption had emptied part of the system. Otherwise, activity between 1993 and 2000 was not accompanied by deformation of the edifice. An eruption in July 2000 was seen from

, and the noise was audible as far as

San Antonio de los Cobres San Antonio de los Cobres is a small town of population 5,482 (per the 2001 INDEC census) in northwestern Argentina. It is the capital of the Los Andes Department of the Salta Province. Geography The town is known for its high elevation of appr ...

, away. The eruption lasted for two hours and formed a

eruption column An eruption column or eruption plume is a cloud of super-heated Volcanic ash, ash and tephra suspended in volcanic gas, gases emitted during an explosive eruption, explosive volcanic eruption. The volcanic materials form a vertical column or Plu ...

. An ash plume was carried east. Three eruptions in October 2002 formed ash columns that rose , while an explosion in December 2003 created a column high. No lava domes were recorded in the crater during that period. Lascar eruption 2006b

Further activity occurred in May 2005, with a ash cloud, and in April 2006. An eruption commenced at 11:35 local time on 18 April 2006. This explosion was strong enough to rattle windows in the school at Talabre. The 18 April eruption was seen from the

El Abra El Abra is the name given to an extensive archeological site, located in the valley of the same name. El Abra is situated in the east of the municipality Zipaquirá extending to the westernmost part of Tocancipá in the department of Cundinama ...

copper mine away and resulted in ash fall north-northeast from the volcano. Four eruptions occurred at 15:20, 17:22, 19:00 and 21:00

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

, forming eruption columns reaching altitudes of . The next day, additional explosions occurred at 15:04, 15:05 and 17:39 UTC, with a maximum column height of . A video taken by the

Chilean Air Force The Chilean Air Force () is the air force of Chile and branch of the Chilean military. History The first step towards the current FACh is taken by Lieutenant Colonel, Teniente Coronel training as a pilot in France. Although a local academy was c ...

on 20 April showed a pit in the floor of the main crater. During the following days, additional explosions generated columns up to high, with little ash production. The eruption ended around 15:32 on 20 April, although some explosions occurred in the following days. Other eruptions were recorded in November 2006 and July 2007. Weak eruptions, characterized by earthquakes and the release of plumes, occurred in February–March 2012 and March–April 2013. Between April and June 2013, glow was observed at the summit, accompanied by the occasional release of gray clouds. Glowing was also reported in October and November 2013. The last eruption, on 30 October 2015, created a column of ash that prompted a raise in the local volcano alert level. This eruption may have been triggered by a precipitation event which added water to the volcan's hydrothermal system. Thermal anomalies from this eruption persisted into 2017 but with a tendency to decrease in number, accompanied by persistent degassing. In December 2022, an explosion generated a high plume. A new

formed inside the active crater in January 2023.

Seismic activity

Seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes (or generally, quakes) and the generation and propagation of elastic ...

activity occurs at Lascar. Research has indicated peculiar patterns, including so called "rapid-fire" events on a background of continuous activity, as well as the occurrence of long-period earthquakes; here and in other volcanoes, this kind of seismic activity is associated with intense fumarolic activity that occurs in the absence of outright eruptions.

Harmonic tremor A harmonic tremor is a sustained release of seismic and infrasonic energy typically associated with the underground movement of magma, the venting of volcanic gases from magma, or both in volcanoes, and with repetitive stick-slip or other impulsi ...

has been recorded at Lascar, perhaps caused by a hydrothermal system. Such tremors may be produced by the movement of liquid materials in the volcano. With the exception of the 1993 eruption, seismic activity associated with eruptions has been sparse. A number of earthquakes were recorded in early February 2012. Between January 2014 and June 2016, about 2–4 volcano-tectonic earthquakes per month were recorded. Long-period earthquakes with magnitudes not exceeding 1.3 were also recorded, with a maximum of 209 events noted in May 2015.

Monitoring and threats

Because of the volcano's remote location, much information on its activity comes from

. Lascar's activity has been monitored by

Thematic Mapper A Thematic Mapper (TM) is one of the Earth observing sensors introduced in the Landsat program. The first was placed aboard Landsat 4 (decommissioned in 2001), and another was operational aboard Landsat 5 up to 2012. /sup> TM sensors feature seven ...

, which has been used to monitor volcanic activity since 1985, when hot spots were observed on Lascar. The eruptions of April 1993 and September 1986 were both preceded by a reduction of thermal radiation observed by Thematic Mapper. A monitoring network has been built around the volcano beginning from 2010. These include gas monitoring,

seismometer A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The out ...

s, a

weather station A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmosphere of Earth, atmospheric conditions to provide information for weather forecasting, weather forecasts and to study the weather and clima ...

and cameras.

Unmanned aerial vehicle An unmanned aerial vehicle (UAV) or unmanned aircraft system (UAS), commonly known as a drone, is an aircraft with no human pilot, crew, or passengers onboard, but rather is controlled remotely or is autonomous.De Gruyter Handbook of Dron ...

s, occasional

reconnaissance In military operations, military reconnaissance () or scouting is the exploration of an area by military forces to obtain information about enemy forces, the terrain, and civil activities in the area of operations. In military jargon, reconnai ...

flights and infrequent visits to the volcano are also used. The Observatorio Volcanológico de los Andes del Sur in

Temuco Temuco () is a List of cities in Chile, city and Communes of Chile, commune, capital (political), capital of the Cautín Province and of the Araucanía Region in southern Chile. The city is located south of Santiago de Chile, Santiago. The cit ...

also employs

webcam A webcam is a video camera which is designed to record or stream to a computer or computer network. They are primarily used in Videotelephony, video telephony, live streaming and social media, and Closed-circuit television, security. Webcams can b ...

s to watch Lascar. The local

Atacameno The Atacama people, also called Atacameño, are an Indigenous people from the Atacama Desert and altiplano region in the north of Chile and Argentina and southern Bolivia, mainly the Antofagasta Region. According to the Argentinean Census in 2010 ...

people have criticized SERNAGEOMIN's volcano monitoring activities, with one responded deeming it too technology-heavy. The

National Geology and Mining Service 250px, Sernageomin building in Providencia, Santiago. The National Geology and Mining Service (; SERNAGEOMIN) is a Chilean government agency. Its function is to provide geological information and advice, technical assistance to government, public ...

of Chile considers Lascar Chile's 14th most dangerous volcano, and in 2020 classified it as a "type I" volcano. It and the Argentine volcano monitoring agency publish volcano alert levels for Lascar. SERNAGEOMIN has created a volcano hazard map for the volcano. Explosive eruptions and ash falls are the major threat to humans from Lascar. The frequent smaller explosive events commonly occur unexpectedly and can thus endanger people on the mountain. The towns of Tumbres and Talabre may be affected by pyroclastic flows, and ash falls can occur east of the volcano. Such ash falls could potentially hit the towns of

, Talabre and

as well as the

Llano de Chajnantor Observatory Llano de Chajnantor Observatory is the name for a group of astronomy, astronomical observatory, observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Reg ...

, the San Pedro de Atacama–Paso de Jama–Jujuy international road and the Sico Pass. Past eruptions caused ash fall in Argentina and disruption of

and could have major effects in the

Salta Province Salta () is a Provinces of Argentina, province of Argentina, located in the northwest of the country. Neighboring provinces are from the east clockwise Formosa Province, Formosa, Chaco Province, Chaco, Santiago del Estero Province, Santiago del Es ...

in case of renewed activity. In 1982, the town of Talabre was moved for safety reasons stemming from flooding and volcanic activity, and ballistic blocks ejected by the volcano are a threat to

mountaineer Mountaineering, mountain climbing, or alpinism is a set of outdoor activities that involves ascending mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas that have become sports ...

s and scientists working on Lascar.

Sector collapse A sector collapse or lateral collapse is the structural failure and subsequent collapse of a minimum volume of of a volcano. Unlike smaller flank collapses, a sector collapse can involve the central volcanic pipe and historically this term had b ...

and

lahars A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are often extremely destructiv ...

have occurred in the past, but are unlikely to be present-day hazards. Heavy metal exposure is a problem for the region. High quantities of arsenic have been observed in local crops; Lascar is one of its major sources in northern Chile.

Thallium Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...

from the volcano is a pollution hazard in the Talabre area. High

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

concentrations in crops from Talabre appear to be caused by volcanic activity as well.

Climate and biota

The area around Lascar is one of the driest and highest volcanic settings in the world. Precipitation at Lascar is about and consists mostly of snow. Persistent snow cover exists on the western and southern slopes of the volcano; it contributes partly to the fumarole water. Steam explosions caused by rainfall have been reported. In 1993, yearly precipitation at several towns around Lascar ranged from . Lascar is located close to the

Atacama Desert The Atacama Desert () is a desert plateau located on the Pacific Ocean, Pacific coast of South America, in the north of Chile. Stretching over a strip of land west of the Andes Mountains, it covers an area of , which increases to if the barre ...

, one of the world's driest deserts. During the

glacial period 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 betw ...

s, the volcano most likely featured small

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

s. The equilibrium line at Lascar was at an altitude of during the

last glacial maximum The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent between 26,000 and 20,000 years ago. Ice sheets covered m ...

. Traces of glaciation also exist at Cerros de Saltar. The end of glaciation may have accompanied an increase in volcanic activity, a phenomenon that has been noted at other volcanoes. 8,500 years ago, the climate in the region became much drier, and the amount of erosion decreased substantially. Temperatures in the surrounding region range between . Measurements made on the southwest rim of the main crater in 2009–2012 indicated air temperatures of . The present-day permanent

snowline The climatic snow line is the boundary between a snow-covered and snow-free surface. The actual snow line may adjust seasonally, and be either significantly higher in elevation, or lower. The permanent snow line is the level above which snow wil ...

in the region lies at an altitude of , higher than the summit of Lascar. Due to the dry climate, there is little vegetation at Lascar.

Bunch grass Tussock grasses or bunch grasses are a group of grass species in the family Poaceae. They usually grow as singular plants in clumps, tufts, hummocks, or bunches, rather than forming a sod or lawn, in meadows, grasslands, and prairies. As perennia ...

and

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

s grow on the volcano's slopes. In the deep valleys,

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

and

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

s support more plants. Volcanic activity at Lascar affects neighbouring ecosystems such as the Aguas Calientes

crater lake Crater Lake ( Klamath: ) is a volcanic crater lake in south-central Oregon in the Western United States. It is the main feature of Crater Lake National Park and is a tourist attraction for its deep blue color and water clarity. T ...

and Laguna Lejia;

flamingo Flamingos or flamingoes () are a type of wading bird in the family Phoenicopteridae, which is the only extant family in the order Phoenicopteriformes. There are four flamingo species distributed throughout the Americas (including the Caribbe ...

s disappeared from the latter after the 1993 eruption and did not return until 2007. Other reports claim that flamingos remained; other animals like

donkey The donkey or ass is a domesticated equine. It derives from the African wild ass, ''Equus africanus'', and may be classified either as a subspecies thereof, ''Equus africanus asinus'', or as a separate species, ''Equus asinus''. It was domes ...

s and

llama The llama (; or ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the pre-Columbian era. Llamas are social animals and live with ...

s were seen around the volcano one day after its eruption.