Sollipulli

Coordinates: 38°58′30″S 71°31′12″W / 38.97500°S 71.52000°W / -38.97500; -71.52000
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Sollipulli
Aerial photograph of volcan Sollipulli, looking southeast. The dark red feature on the side of Sollipulli is the cinder cone called Chufquen which formed during the most recent eruption, about 700 years ago.
Highest point
Elevation2,282 m (7,487 ft)[1]
ListingList of volcanoes in Chile
Coordinates38°58′30″S 71°31′12″W / 38.97500°S 71.52000°W / -38.97500; -71.52000[1]
Geography
Sollipulli is located in Chile
Sollipulli
Sollipulli
Location of Sollipulli
in Chile
LocationSouthern Chile
Southern Volcanic Zone of the Andes
Last eruption1240 ± 50 years[1]

Sollipulli (Spanish pronunciation:

Southern Volcanic Zone of the Andes, one of the four volcanic belts in the Andes chain
.

The volcano has evolved in close contact with glacial ice. It differs from many calderas in that Sollipulli appears to have collapsed in a non-explosive manner. The age of collapse is not yet known, but it is presently filled with ice to thicknesses of 650 m (2,130 ft). The ice drains through two glaciers in the west and the north of the caldera. Sollipulli has developed on a basement formed by Mesozoic and Cenozoic geological formations.

Sollipulli was active in the

scoria cone
on the northern flank. Sollipulli is among the 118 volcanoes which have been active in recent history.

Geomorphology and geography

Sollipulli lies in the Araucanía Region, Cautín Province, Melipeuco commune.[3] The Sollipulli volcano is in the western part of the Nevados de Sollipulli mountain range, which is bordered to the north, south and east by river valleys.[4] The communes of Curarrehue, Cunco, Panguipulli, Pucón and Villarrica are in the area,[5] Melipeuco lies 20 km (12 mi) northwest.[6] The volcano is also part of the Kütralkura geopark project.[7]

Regional

Sollipulli is part of the

Austral Volcanic Zone (south of the Southern Volcanic Zone). These volcanic zones are separated by gaps where there is no volcanic activity and the subduction of the Pacific Ocean crust is shallower than in the volcanically active areas. About 60 volcanoes have erupted in historical time in the Andes, and 118 additional volcanic systems show evidence of Holocene eruptions.[9]

There are 60 volcanoes in the Southern Volcanic Zone; among these are

Cerro Hudson, which experienced large eruptions in 1932 and 1991 that resulted in the emission of substantial volumes of ash. The volcanoes Llaima and Villarrica have been regularly active during recent history.[9]

Local

Sollipulli is a stratovolcano,[4] which has one 4 km-wide (2.5 mi) caldera on its summit and southwest of it the 1 km-wide (0.62 mi) Alpehué crater.[6] The crater is draped by pyroclastic flow deposits, and its rim reaches a height of 200 m (660 ft).[10] The rims of the caldera rise 150 m (490 ft) above the ice in the caldera;[11] the highest summit of Sollipulli lies on the southern flank of the caldera and reaches an elevation of 2,282 m (7,487 ft) above sea level.[4] On the southern and eastern side the caldera is bordered by several lava domes.[1] The caldera most likely was not formed by a large explosive eruption, considering that no deposits from such an eruption have been found.[12] An older 5 km × 4 km-wide (3.1 mi × 2.5 mi) caldera underlies the summit caldera.[13]

The volcano is formed by

lava flows, lava domes, scoria, pillow lavas as well as pumice falls, pyroclastics and other material.[14] The edifice has a volume of about 85 km3 (20 cu mi) and covers a surface area of about 250 km2 (97 sq mi). Radial valleys extend away from the top.[4] A number of particular landforms on Sollipulli formed under the influence of glacial ice, such as the caldera structure.[15]

The Nevados de Sollipulli mountain chain west of the Sollipulli caldera are a chain of volcanoes which is heavily eroded. They are formed by

lava flows; glacial action has left cirques. Closer to the caldera they are better preserved, with individual flows issuing from fissure vents.[16] This chain is one of several east–northeast striking volcano alignments in the Southern Volcanic Zone, the regional tectonics favour magma ascent along such alignments.[17]

The flanks of the volcano are covered by

lava flows;[6] about a dozen such craters dot the flanks of the volcano.[19]

Glaciers

Both the main caldera and the Alpehué crater contain glaciers,[6] which in the caldera reached a thickness of 650 m (2,130 ft) in 1992[20] and fills it;[6] the total volume was estimated at 6 km3 (1.4 cu mi) in 1992.[21] These glaciers feature typical ice structures such as crevasses and there may be a subglacial lake in the caldera.[14] Three lakes are found in the caldera at its margins, the easterly Sharkfin lake, the southeasterly Dome lake and the southwesterly Alpehué lake. These glaciers drain to the north and northwest; the latter glacier flows from the caldera through the Alpehué crater into the valley of the same name,[11] which is drained by the Rio Alpehué into the Rio Allipén river.[6] Other than the caldera and crater glaciers, the only snow cover on Sollipulli is seasonal.[8] Glaciers have been present on the volcano before the Last Glacial Maximum[22] and have left glacial striations and evidence of subglacial eruptions such as hyaloclastite deposits.[23]

The glacier within the caldera of Sollipulli is shrinking;[24] its surface area decreased between 1961 and 2011 and the Alpehuén outlet glacier retreated by 1.3 km (0.81 mi).[25] Some smaller ice fields around Sollipulli either shrank between1986 and 2017 or disappeared altogether.[26] The process of glacier retreat is probably accelerated by ash being deposited on the glacier through eruptions at the neighbouring volcano Puyehue-Cordón Caulle; activity at the other volcanoes Llaima and Villarrica may have the same effect.[24] In 2011, the volume of the glacier was 4.5 ± 0.5 km3 (1.08 ± 0.12 cu mi).[8] Melting of the glacier risks generating lahars and putting water supplies in the region into jeopardy.[24]

  • Nevados de Solipulli seen from Villarrica volcano
    Nevados de Solipulli seen from Villarrica volcano
  • Sollipulli caldera viewed from space, east is up
    Sollipulli caldera viewed from space, east is up
  • The caldera glacier of Sollipulli
    The caldera glacier of Sollipulli
  • Aerial photograph of Sollipulli Caldera looking east
    Aerial photograph of Sollipulli Caldera looking east

Geology

Subduction has been ongoing on the western side of South America since 185 million years ago and has resulted in the formation of the Andes and volcanic activity within the range. About 27 million years ago, the Farallon Plate broke up and the pace of subduction increased, resulting in increased volcanic activity and a temporary change in the tectonic regime of the Southern Andes.[9]

Sollipulli volcano developed on a 600-to-1,600-metre-high (2,000–5,200 ft) basement which consists of the

Liquiñe-Ofqui Fault Zone and the Reigolil-Pirihueico fault, pass west and east of Sollipulli, respectively. They are connected by east–west trending faults[28]

Composition

Rocks erupted from Sollipulli range from

orthopyroxene, plagioclase and titanomagnetite.[29] Xenoliths are also found, including diorite and granophyre.[30]

The petrogenesis of the Alpehué rocks has been explained with the penetration of more primitive magma into a dacitic magma chamber, which was then subject to magma mixing. The primitive magmas sometimes pass through the flanks of the edifice and form parasitic vents in these cases.[31]

Obsidian was obtained on Sollipulli and exported over large distances; it has been found as far as Argentina's steppes and northern Chile,[5] and is chemically and in appearance different from obsidian obtained on Chaitén volcano. One source has been identified at a lava dome on the western side of Sollipulli.[32] A route starting south of Melipeuco leads up on the volcano; this route was used for the transport of obsidian in the 1980s.[5]

Precipitation and vegetation

Annual precipitation amounts to 2.1 metres per year (6.9 ft/a) and mostly falls between April and September.

mallines which were used for grazing.[32]

Eruption history

Sollipulli was active during the

argon-argon dating having obtained ages of 490,000 ± 30,000 and 312,000 ±  20,000 years ago.[33] Six separate volcanic units form the edifice; from the oldest to the youngest they are the Sharkfin, Northwest, South, Peak, Alpehué and Chufquén units. The first two may be contemporaneous to the formation of the caldera, or they may predate it.[14] The Sharkfin unit was emplaced in a subglacial environment and later disrupted by faulting,[34] later units show substantial evidence of having been altered by glaciers.[10] Radiometric dates have been obtained on the Sharkfin unit (700,000 ± 140,000 and 350,000 ± 90,000 years before present), the Northwest unit (120,000 ± 16,000, 120,000 ± 140,000, 110,000 ± 30,000 and 100,000 ± 30,000 years before present) and the South and Peak units (68,000 ± 14,000, 64,000 ± 15,000 and 26,000 ± 5,000 years before present).[33] The caldera is nested within an older and eroded caldera,[19] and some parasitic cones are heavily eroded whereas others appear to be younger.[35]

Biobio River via the Rio Litrán, thus redirecting its flow into the Atlantic Ocean.[48]

Radiocarbon dating at Chufquén has yielded an age of 710 ± 60 years before present.[6] This eruption deposited ash onto the caldera ice, while it is absent from the central parts of the Chufquén valley; either it was removed by a later glacier advance or it landed on a glacier which later retreated.[30] The eruption occurred relatively recently, indicating that Sollipulli is still active.[4] Presently, fumaroles and geothermal phenomena occur at the northwestern foot of Sollipulli.[49]

The 0.2 km2 (0.077 sq mi)

sinter deposits[51] that form small terrace structures.[50] Geyser columns reach 2.5 m (8 ft 2 in) height when they erupt.[51] The geyser field has been active since at least 7,400 years. The deep incision and fractured rocks may facilitate the ascent of geothermal waters.[50]

Hazards

The substantial ice body in the caldera means that there is a significant risk of mudflows or

Cerro Hudson volcano.[53]

The Chilean geological service

Sernageomin monitors the volcano and publishes a hazard index for it. The towns of Cunco, Melipeuco and Villa García are close to the volcano.[3] Melipeuco has devised a Volcanic Emergency Plan to deal with future eruptions of Llaima or Sollipulli.[54]

Notes

  1. ^ Lahars are volcanic debris flows, where sediment is dissolved in hot water.[43]
  2. ^ A volcanic explosivity index of 5 refers to a "cataclysmic" or "paroxysmal" eruption which ejects between 1 and 10 km3 (0.24–2.40 cu mi) of rocks.[45]

References

  1. ^ a b c d e "Sollipulli". Global Volcanism Program. Smithsonian Institution.
  2. ISSN 2411-1236
    .
  3. ^
    SERNAGEOMIN. Archived from the original
    on 5 October 2017. Retrieved 16 November 2017.
  4. ^ a b c d e Naranjo et al. 1993, p. 168.
  5. ^
    ISSN 0718-1795
    . Retrieved 15 November 2017.
  6. ^ a b c d e f g h Gilbert et al. 1996, p. 67.
  7. S2CID 134884114
    .
  8. ^ a b c Lachowycz et al. 2015, p. 60.
  9. ^
    ISSN 0716-0208
    .
  10. ^ a b c Gilbert et al. 1996, p. 73.
  11. ^ a b Gilbert et al. 1996, p. 69.
  12. ^ a b Gilbert et al. 1996, p. 81.
  13. ^ a b Munoz-Saez et al. 2020, p. 2.
  14. ^ a b c d Gilbert et al. 1996, p. 70.
  15. ^ Lachowycz et al. 2015, p. 76.
  16. ^ a b Naranjo et al. 1993, p. 170.
  17. ISSN 1944-9194
    .
  18. ^ Gilbert et al. 1996, p. 68,69.
  19. ^ a b c d Naranjo et al. 1993, p. 169.
  20. ISSN 1852-7744
    .
  21. ^ Gilbert et al. 1996, p. 79.
  22. ISSN 1851-8249
    .
  23. ^ a b c Munoz-Saez et al. 2020, p. 3.
  24. ^
    Bibcode:2011AGUFMEP51B0846H
    .
  25. hdl:10533/130506
    .
  26. ^ Reinthaler et al. 2019, p. 551.
  27. ^ Naranjo et al. 1993, p. 169,170.
  28. ^ Munoz-Saez et al. 2020, pp. 2–3.
  29. ^ Gilbert et al. 1996, p. 71,72.
  30. ^ a b c Gilbert et al. 1996, p. 75.
  31. ^ Naranjo et al. 1993, p. 185.
  32. ^
    ISSN 0718-2244
    .
  33. ^ a b Lachowycz et al. 2015, p. 62.
  34. ^ Gilbert et al. 1996, p. 71.
  35. ^ Naranjo et al. 1993, p. 173.
  36. ^ Moreno-Gonzalez 2022, p. 3.
  37. ^ Moreno-Gonzalez 2022, p. 1.
  38. ^ Dickson et al. 2021, p. 539.
  39. S2CID 233314063
    .
  40. S2CID 134334049
    .
  41. doi:10.1029/2005JD006072
    .
  42. S2CID 133976863
    .
  43. doi:10.1146/annurev.fl.13.010181.000421
    .
  44. ^ Naranjo et al. 1993, p. 177,178.
  45. OCLC 904547525
    .
  46. ^ Dickson et al. 2021, p. 545.
  47. S2CID 233937137
    .
  48. ^ Isla, Federico Ignacio (1 June 2017). "Sollipulli. El volcán cuyas cenizas definieron una frontera internacional treinta siglos después". Ciencia Hoy (in Spanish). 26 (155). Asociación Civil Ciencia Hoy: 34–38.
  49. S2CID 135109592
    .
  50. ^ a b c Munoz-Saez et al. 2020, p. 10.
  51. ^ a b Munoz-Saez et al. 2020, p. 4.
  52. ^ Reinthaler et al. 2019, p. 553.
  53. ^ Naranjo et al. 1993, p. 186.
  54. ISSN 0719-5370
    .

Sources

External links
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