| Cerro del Azufre | |
|---|---|
 Cerro del Azufre. | |
| Highest point | |
| Elevation | 5,846 m (19,180 ft)[1] |
| Coordinates | 21°47′13″S68°14′13″W / 21.787°S 68.237°W /-21.787; -68.237[1] |
| Geography | |
  Cerro del Azufre Location of Cerro del Azufre in Chile | |
| Location | Chile |
| Parent range | Andes |
| Geology | |
| Mountain type | Stratovolcano |
| Last eruption | Unknown |
Cerro del Azufre (Spanish pronunciation:[ˈseroðelaˈsufɾe]) is astratovolcano located inEl Loa Province,Antofagasta Region,Chile. It is part of a chain of volcanoes that separate UpperLoa River basin from the endorheicSalar de Ascotán basin and is flanked to the west by adaciticlava dome called Chanka or Pabellón. The 6000 metre volcanoesSan Pedro andSan Pablo are located to the southwest of Cerro del Azufre.
Cerro del Azufre lies in northern Chile, close to the border with Bolivia and south of theSalar de Ascotan.[2]Route 21-CH [es]highway, which passes northwest from the volcano,[3] connects the city ofCalama withOllagüe town.[4] Formerly, theInca road system passed east of the volcano.[5]Sulfur was mined on the mountain in the past.[6]
With a diameter of 14 kilometres (8.7 mi),[7] the volcano is one of the largest in the area,[8] and reaches a height of 5,846 metres (19,180 ft).[1][7] It consists of two overlapping volcanic edifices,[9] with the northern having two vents and the southern three;[10] each edifice has asummit crater[11] and there are reportedlycrater lakes.[12] They are separated by about 2 kilometres (1.2 mi) ofhydrothermally altered terrain, where there are threemining areas. The northern edifice bears evidence of asector collapse that produced a northwarddebris avalanche,[11] which was later buried by lava flows.[1] The southern edifice hasmoraine deposits[11] andgorges formed by erosion;[10] there are also traces ofrock glaciers.[13] The Chac-Inca andCerro Chankalava domes lie east and west, respectively, between the two edifices of Cerro del Azufre.[11]
The area is dominated by volcanoes that often reach over 6,000 metres (20,000 ft) elevation[14] and are ofMiocene toHolocene age. Neighbouring volcanoes includeSan Pedro andSan Pablo to the south, Carasilla to the northwest and theApacheta-Aguilucho volcanic complex to the east[2] which is sometimes grouped with Cerro del Azufre.[15] Cerro del Azufre and neighbouring volcanoes to the southeast[16] form the Azufre-Inacaliri volcanic chain, which is formed mainly bylava flows with compositions ranging frombasaltic andesite torhyolite.[17]
During the last 10 million years,caldera eruptions in theAltiplano-Puna volcanic complex (APVC) have generatedignimbrites and lavas which underlie Cerro del Azufre. The APVC is linked to theAltiplano-Puna Magma Body under theAltiplano;[17] the latter is the highest volcanic plateau in the world.[14] It has a volume of about 500,000 cubic kilometres (120,000 cu mi) of partially molten rock and may be the source of heat for geothermal fields, of magma forlava domes that were emplaced in the area during the last 120,000 years[16] and of the Azufre magma.[18] Northwest-southeast trendingstrike-slip faults run across thevolcanic arc and appear to have influenced both the volcanic activity and the formation ofore deposits; they include the Azufre-Inacaliri lineament that Cerro del Azufre is part of.[19] The Pabelloncitograben formed in the Azufre-Inacaliri chain when the volcanoes spread under their own weight and deformed during thePliocene-Quaternary.[17]
Volcanic rocks from Cerro del Azufre define anandesite todacite suite, withplagioclasephenocrysts.[20] The pathways of magma formation are poorly elucidated but appear to have taken place at two different depths under the volcano.[21]Hydrothermal alteration has producedalunite,gypsum,hematite,kaolinite andsulfur.[10]Isotope ratios indicate that distinct components went into forming the erupted magmas, including possible below-volcanic arc magmas andhydrothermally altered rocks.[22] The magma would be stored at two levels, and eruptions took place when magma from the lower level entered the upper level.[23]
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 oflava flows andpyroclastic flows less than 2 metres (6 ft 7 in) thick; thesector 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.[24] The fourth stage makes up the northern edifice and the conspicuous lava flows there.[25] 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 thelate glacial 20,000 years ago.[20] The volcano grew at a rate of 0.01–0.2 cubic kilometres per kiloare (2.2×10−9–4.46×10−8 cu mi/sq ft), which is typical for volcanoes in the region.[26] Several lava domes such as Chac-Inca, Pabellón and Chanca grew around the volcano.[23] Despite the young appearance of the volcanic features, none of its structures have yielded ages of less than 80,000 years[1] and the volcano is consideredextinct.[27] Current geomorphic processes includelandslides.[28]
While there are no active hydrothermal structures at Cerro del Azufre,[21] traces of extinctfumaroles are found on the western flank of the northern edifice, and activehot springs with temperatures of about 42 °C (108 °F) occur at the northern foot of Cerro del Azufre.[10]Seismic tomography[29] andelectrical conductivity analysis has identified a zone under the volcano that may be either amagma chamber or a hydrothermal system.[30] Cerro Pabellón is one of severalgeothermal fields in this part of the Andes and as of 2022[update] the only one wheregeothermal power is being produced. The field reaches the surface in theApacheta-Aguilucho volcanic complex but may extend over an area of 25 square kilometres (9.7 sq mi) underground.[2]