Quetrupillán ("blunted", "mutilated"; also known as Ketropillán) is a stratovolcano located in

Los Ríos Region The Los Ríos Region (Spanish: ''Región de Los Ríos'', , ''Region of the Rivers'') is one of Chile's 16 regions, the country's first-order administrative divisions. Its capital is Valdivia. It began to operate as a region on October 2, 2007 ...

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

. It is situated between Villarrica and

Lanín Lanín is an ice-clad, cone-shaped stratovolcano on the border of Argentina and Chile. It forms part of two national parks: Lanín in Argentina and Villarrica in Chile. It is a symbol of the Argentine province of Neuquén, being part of its f ...

volcanoes, within

Villarrica National Park Villarrica National Park is located in the Andes, in the La Araucanía and Los Ríos regions of Chile, near Pucón. The centerpiece of the park is a line of three volcanoes stretching transversely to the Andean range: Villarrica, Quetrupillán ...

. Geologically, Quetrupillán is located in a tectonic basement block between the main traces of

Liquiñe-Ofqui Fault The Liquiñe-Ofqui Fault is major geological fault that runs a length of roughly in a NNE-SSW orientation and exhibits current seismicity. It is located in the Chilean Northern Patagonian Andes. It is a dextral intra-arc strike-slip fault. Most ...

(to the west) and

Reigolil-Pirihueico Fault The Reigolil-Pirihueico Fault (Spanish: ''Falla Reigolil-Pirihueico'') is a second-order geological fault located in the Chilean and Argentine Andes. As the name implies, it runs from Pirihueico Lake to Reigolil Valley. Reigolil-Pirihueico Fault ru ...

(to the east). The volcano consists of one stratovolcano with a summit

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

, and is constructed within a field of smaller centres and a larger caldera. It was active during the late

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

; some large eruptions occurred during the

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

as well.

Geology and geography

The volcano is situated in the

Curarrehue Curarrehue () is a town and commune in Cautín Province of Araucanía Region, Chile. The origin of Curarrehue dates back to the occupation of Araucanía and the Conquest of the Desert by the Chilean and Argentine army respectively in the 1870s and ...

Pucón Pucón (Mapudungun: "entrance to the cordillera") is a Chilean city and commune administered by the municipality of Pucón https://www.mipucon.com/ sitio web. It is located in the Province of Cautín, Araucanía Region, 100 km to the south ...

and

Panguipulli Panguipulli ( ; Mapudungun for "hill of the puma") is a city and commune in Valdivia Province, southern Chile, administered by the Municipality of Panguipulli. It is located on the western edge of Panguipulli Lake, and is on a moraine in the Ch ...

municipalities A municipality is usually a single administrative division having corporate status and powers of self-government or jurisdiction as granted by national and regional laws to which it is subordinate. The term ''municipality'' may also mean the go ...

of the Cautín and

Valdivia Valdivia (; Mapuche: Ainil) is a city and commune in southern Chile, administered by the Municipality of Valdivia. The city is named after its founder Pedro de Valdivia and is located at the confluence of the Calle-Calle, Valdivia, and Cau-Cau R ...

provinces. Towns close to Quetrupillán are Catripulli, Currarehue and Puesco. It is considered Chile's 21st most dangerous volcano.

Regional

Off the western coast of South America, the Nazca Plate

subduct Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

s beneath the South American Plate in the Peru-Chile Trench. As the plate subducts, it releases water into the overlying mantle and causes it to melt, gives rise to 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 American ...

of the Andes. The rate and geometry of subduction has varied over time. During the last six million years, the subduction process has been oblique and as a consequence, the

has developed within the

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

and dominates the regional tectonics. Quetrupillán lies on the border between

and

Araucanía Region The Araucanía ( ), La Araucanía Region ( es, Región de La Araucanía ) is one of Chile's 16 first-order administrative divisions, and comprises two provinces: Malleco in the north and Cautín in the south. Its capital and largest city is Te ...

, in the

. Together with Villarrica and

it forms a northwest-southeast alignment of volcanoes, which coincides with the Mocha-Villarrica

transcurrent fault In geology, a fault is a Fracture (geology), planar fracture or discontinuity in a volume of Rock (geology), rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust (geolo ...

. The Cordillera El Mocho and Quinquilil volcanoes are likewise situated on this alignment, both are deeply eroded composite volcanoes of small dimensions. Other volcanoes in the Southern Volcanic Zone have similar alignments, such as

Nevados de Chillán Nevados de Chillán is a group of stratovolcanoes located in the Andes of Ñuble Region, Central Chile, and is one of the most active volcanoes in the region. It consists of three overlapping peaks, Cerro Blanco (Volcán Nevado) at the northwe ...

and

Puyehue-Cordón Caulle Puyehue (; ) and Cordón Caulle are two coalesced volcanic edifices that form a major mountain massif in Puyehue National Park in the Andes of Ranco Province, in the South of Chile. In volcanology this group is known as the Puyehue-Cordón Cau ...

. In comparison to Villarrica, Quetrupillán has been less active and its eruptions were also smaller than Villarrica's, with no large

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

s found at Quetrupillán.

Local

Quetrupillán is a high composite stratovolcano and a shrinking

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

cover; the existence of

s is unconfirmed. The entire edifice has a north-south elongated shape and covers a ground surface of . The volcano contains a field of lava domes, maars and

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 ...

s that occupy a surface of . These subsidiary vents include the scoria cone Huililco, the Volcanes de Llancahue and the Volcanoes de Reyehueico. There are in total 16 lateral vents, of which 12 are found in a

volcanic field A volcanic field is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes ...

south of Quetrupillán.

Fissure vent A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilom ...

s of

age occur on the southern side of the volcano. The small volume of the main Quetrupillán edifice and the widespread vents may reflect the interaction between the volcano and the Liquiñe-Ofqui fault, which generated secondary vents whose location was controlled by the Liquiñe-Ofqui fault, the Mocha-Villarrica fault and local structures. There are two lakes on the southern flank, Laguna Azul to the southwest and Laguna Blanca to the southeast. A number of eruption products show traces of ice-

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

interactions.

Tuff ring Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...

s and maars formed through the interaction of magma with

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

. A

geomagnetic Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic ...

anomaly at shallow depth south of the volcano may be a pluton associated with a

resurgent dome In geology, a resurgent dome is a dome formed by swelling or rising of a caldera floor due to movement in the magma chamber beneath it. Unlike a lava dome, a resurgent dome is not formed by the extrusion of highly viscous lava onto the surfac ...

. Huililco scoria cone has produced two lava flows and is considered to be also part of the Quetrupillán volcanic complex. Three different

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 secondar ...

s make up the basement of Quetrupillán: The

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

Panguipulli, the possibly

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Currarehue and the

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 ...

Trápatrapa formations and plutonic rocks. These are plutonic and

volcaniclastic Volcaniclastics are geologic materials composed of broken fragments ( clasts) of volcanic rock. These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it ...

rock units. The Villarrica-Quetrupillán volcanic chain forms a geological boundary, since the Patagonian Batholith crops out south of it.

Composition

Volcanic rocks at Quetrupillán have a bimodal composition, ranging from

basalt 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 ...

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

, and overall more silicic than the rocks erupted by Villarrica and Lanín. Unusually for the region,

trachydacite Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and alk ...

also occurs at the volcano. These contain

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

s of

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

and pyroxene, with additional microphenocrysts 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, printing ...

and

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

. Based on the composition, it has been inferred that the magma reservoir of Quetrupillán contained a mush of crystals, from which magma was repeatedly mobilized following the injection of fresh magmas that reheated the mush. Fractional crystallization of basalts generated

trachytic Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and ...

melts. A tectonic regime associated with the Liquiñe-Ofqui Fault which prevents magma from simply ascending to the surface may help the magma evolution processes.

Eruptive history

Eruptive activity at Quetrupillán commenced before the

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

s. The first phase of activity involved the formation of calderas and stratovolcanoes; later during the ice ages lava flows and

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

s were emplaced. Finally, the present stratovolcano was emplaced towards the end of glaciation; parasitic vents formed even later and produced lava flows. Quetrupillán has erupted pyroclastics, which have formed flow and

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

deposits east of the volcano. Several phases of volcanic activity have been inferred from the deposits; most of them feature either

ous or

scoria Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) '' ...

ceous

deposits with varying contents of juvenile lapilli,

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 to ...

and ash fall deposits. * The ''Moraga sequence'' was formed 12,720 ± 40 – 12,690 ± 40 years

Before Present Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becau ...

(BP) during one rather prolonged eruption. * The ''Puala sequence'' was formed 10,240 ± 40 years BP. * The ''Trancura sequence'' was formed 8,680 ± 40 years BP and has a similar composition to the ''Avutardas sequence''. * The ''Carén sequence'' was formed 3,800 ± 30 years BP. * The ''Correntoso sequence'' was formed 2,930 ± 30 years BP. * The ''Trancas Negras sequence'' was formed 2,060 ± 30 years BP. * The ''Puesco sequence'' was formed 1,650 ± 70 years BP, during the largest known eruption of Quetrupillán. This eruption created a high

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 volcanic eruption. The volcanic materials form a vertical column or Plume (fluid dynamics), ...

and deposited about of rock. A volcanic explosivity index of 4 has been assigned to this event. * The ''Carén sequence'' was formed 1,380 ± 30 years BP, it is the youngest explosive eruption of Quetrupillán. In addition, three

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

s in neighbouring lakes dated to 16,748–16,189, 15,597–12,582 and 12,708–12,567 years Before Present may originate from Quetrupillán but they have also been attributed to

Sollipulli Sollipulli (; in the Mapuche language) is an ice-filled volcanic caldera and volcanic complex, which lies southeast of the small town of Melipeuco in the La Araucanía Region, Chile. It is part of the Southern Volcanic Zone of the Andes, one o ...

. All these tephras are of

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

rhyodacitic 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 ...

composition and the eruptions that generated them have an estimated volcanic explosivity index of 3. Reports exist of eruptions during the 19th century, one eruption was reported in 1872. Explosive activity has a recurrence interval of about 1,200 years, which given the age of the last event carries significant implications with regards to the volcanic hazard of Quetrupillán.

Mythology

According to a tale from

Mapuche The Mapuche ( (Mapuche & Spanish: )) are a group of indigenous inhabitants of south-central Chile and southwestern Argentina, including parts of Patagonia. The collective term refers to a wide-ranging ethnicity composed of various groups who s ...

mythology, originally there were just two volcanoes:

Choshuenco Choshuenco is a village ( es, aldea) on the eastern edge of Panguipulli Lake in Panguipulli commune, Los Lagos Region, Chile. It is south of the 203-CH route that goes from Lanco to Huahum Pass. It is west of the Argentina Argentina ...

and

. Then the volcano ( Villarrica) fought the other two volcanoes in a century-long conflict; eventually Ruka Pillan was victorious, coinciding with the beginning

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

contest.

Vegetation

, vegetation on Quetrupillán included ''

Araucaria araucana ''Araucaria araucana'' (commonly called the monkey puzzle tree, monkey tail tree, piñonero, pewen or Chilean pine) is an evergreen tree growing to a trunk diameter of 1–1.5 m (3–5 ft) and a height of 30–40 m (100–130 ft). ...

'' and ''

Nothofagus antarctica ''Nothofagus antarctica'' (''Antarctic beech''; in Spanish ''Ñire'' or ''Ñirre'') is a deciduous tree or shrub native to southern Chile and Argentina from about 36°S to Tierra del Fuego (56° S), where it grows mainly in the diminishing tempe ...

'' forests, as well as puna-like vegetation.