Английская Википедия:Cerro del Azufre

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Шаблон:Short description

Шаблон:Infobox mountain Шаблон:Commons category Cerro del Azufre (Шаблон:IPA-es) is a stratovolcano located in El Loa Province, Antofagasta Region, Chile. It is part of a chain of volcanoes that separate Upper Loa River basin from Salar de Ascotán basin and is flanked to the west by a dacitic lava dome called Chanka or Pabellón. The 6000 metre volcanoes San Pedro and San Pablo are located to the southwest of Cerro del Azufre.

Geography and geomorphology

Cerro del Azufre lies in northern Chile, close to the border with Bolivia and south of the Salar de Ascotan.Шаблон:Sfn Шаблон:Ill highway passes northwest from the volcano,Шаблон:Sfn it connects the city of Calama with Ollagüe town.Шаблон:Sfn Formerly, the Inca road system passed east of the volcano.Шаблон:Sfn Sulfur was mined on the mountain in the past.Шаблон:Sfn

With a diameter of Шаблон:Convert,Шаблон:Sfn the volcano is one of the largest in the area,Шаблон:Sfn and reaches a height of Шаблон:Convert.Шаблон:SfnШаблон:Sfn It consists of two overlapping volcanic edifices,Шаблон:Sfn with the northern having two vents and the southern three;Шаблон:Sfn each edifice has a summit craterШаблон:Sfn and there are reportedly crater lakes.Шаблон:Sfn They are separated by about Шаблон:Convert of hydrothermally altered terrain, where there are three mining areas. The northern edifice bears evidence of a sector collapse that produced a northward debris avalanche,Шаблон:Sfn which was later buried by lava flows.Шаблон:Sfn The southern edifice has moraine depositsШаблон:Sfn and gorges formed by erosion;Шаблон:Sfn there are also traces of rock glaciers.Шаблон:Sfn The Chac-Inca and Cerro Chanka lava domes lie east and west, respectively, between the two edifices of Cerro del Azufre.Шаблон:Sfn

The area is dominated by volcanoes that often reach over Шаблон:Convert elevationШаблон:Sfn and are of Miocene to Holocene age. Neighbouring volcanoes include San Pedro and San Pablo to the south, Carasilla to the northwest and the Apacheta-Aguilucho volcanic complex to the eastШаблон:Sfn which is sometimes grouped with Cerro del Azufre.Шаблон:Sfn Cerro del Azufre and neighbouring volcanoes to the southeastШаблон:Sfn form the Azufre-Inacaliri volcanic chain, which is formed mainly by lava flows with compositions ranging from basaltic andesite to rhyolite.Шаблон:Sfn

Geology

During the last 10 million years, caldera eruptions in the Altiplano-Puna volcanic complex (APVC) have generated ignimbrites and lavas which underlie Cerro del Azufre. The APVC is linked to the Altiplano-Puna Magma Body under the Altiplano;Шаблон:Sfn the latter is the highest volcanic plateau in the world.Шаблон:Sfn It has a volume of about Шаблон:Convert of partially molten rock and may be the source of heat for geothermal fields, of magma for lava domes that were emplaced in the area during the last 120,000 yearsШаблон:Sfn and of the Azufre magma.Шаблон:Sfn Northwest-southeast trending strike-slip faults run across the volcanic arc and appear to have influenced both the volcanic activity and the formation of ore deposits; they include the Azufre-Inacaliri lineament that Cerro del Azufre is part of.Шаблон:Sfn The Pabelloncito graben formed in the Azufre-Inacaliri chain when the volcanoes spread under their own weight and deformed during the Pliocene-Quaternary.Шаблон:Sfn

Composition

Volcanic rocks from Cerro del Azufre define an andesite to dacite suite, with plagioclase phenocrysts.Шаблон:Sfn The pathways of magma formation are poorly elucidated but appear to have taken place at two different depths under the volcano.Шаблон:Sfn Hydrothermal alteration has produced alunite, gypsum, hematite, kaolinite and sulfur.Шаблон:Sfn Isotope ratios indicate that distinct components went into forming the erupted magmas, including possible below-volcanic arc magmas and hydrothermally altered rocks.Шаблон:Sfn The magma would be stored at two levels, and eruptions took place when magma from the lower level entered the upper level.Шаблон:Sfn

Eruption history

Volcanic activity at Cerro del Azufre took place in four stages. The first stage crops out at isolated sites on the southern flank, and consists of eroded lava flows; one age of 1.1±0.2 million years may be attributable to this unit. The second stage was emplaced between about 0.7-0.5 million years ago and forms parts of the western and northern parts of Cerro del Azufre. It consists of lava flows and pyroclastic flows less than Шаблон:Convert thick; the sector collapse may have occurred during this stage. The third stage formed between 0.5-0.3 million years ago and is constituted by the southern edifice; it is made up by lava flows and a summit lava dome.Шаблон:Sfn The fourth stage makes up the northern edifice and the conspicuous lava flows there.Шаблон:Sfn It is not precisely dated, but based on the amount of erosion it was subject to it was probably emplaced between 0.3-0.12 million years ago and before the late glacial 20,000 years ago.Шаблон:Sfn The volcano grew at a rate of Шаблон:Convert, which is typical for volcanoes in the region.Шаблон:Sfn Several lava domes such as Chac-Inca, Pabellón and Chanca grew around the volcano.Шаблон:Sfn Despite the young appearance of the volcanic features, none of its structures have yielded ages of less than 80,000 yearsШаблон:Sfn and the volcano is considered extinct.Шаблон:Sfn Current geomorphic processes include landslides.Шаблон:Sfn

Geothermal activity

While there are no active hydrothermal structures at Cerro del Azufre,Шаблон:Sfn traces of extinct fumaroles are found on the western flank of the northern edifice, and active hot springs with temperatures of about Шаблон:Convert occur at the northern foot of Cerro del Azufre.Шаблон:Sfn Seismic tomographyШаблон:Sfn and electrical conductivity analysis has identified a zone under the volcano that may be either a magma chamber or a hydrothermal system.Шаблон:Sfn Cerro Pabellón is one of several geothermal fields in this part of the Andes and Шаблон:As of the only one where geothermal power is being produced. The field reaches the surface in the Apacheta-Aguilucho volcanic complex but may extend over an area of Шаблон:Convert underground.Шаблон:Sfn

See also

References

Шаблон:Reflist

Sources

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Шаблон:Andean volcanoes

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