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Coropuna
View on two summit mountain from over a lake
View of the volcano Coropuna
Highest point
Elevation6,377 m (20,922 ft)[1]
Geography
A topographic map of Peru within South America
A topographic map of Peru within South America
Coropuna
Parent rangeAndes
Geology
Age of rockMiocene-Holocene
Mountain typeVolcano
Volcanic arcCentral Volcanic Zone
Last eruption1,100 ± 100 BP[3]

Coropuna is a volcano in the Andes with an altitude of 6,377 metres (20,922 ft), in the Cordillera Ampato segment of the Peruvian Andes.[1] and 155 kilometres (96 mi) away from Arequipa. It is a volcano constructed mostly from lava flows on a basement formed by Miocene ignimbrites. Coropuna has been active for at least five million years, with the bulk of the current cone forming during the Pliocene-Pleistocene.

The volcano is covered by a thick ice cap, one of the largest in the tropics. This ice cap has existed at least since the Pliocene and has undergone several phases of expansion and reduction. Currently the ice cap is in retreat and one estimate indicates it will disappear by 2045. Interaction between volcanic activity and glacial effects has generated mudflows, which could be a hazard to surrounding populations in case of a return of volcanic activity. The retreat of the Coropuna glaciers threatens the water supply of several ten thousands people.

The mountain was considered sacred by the Inka and a number of archeological sites are found on it.

Geography and Geology

Coropuna is found south of the Pucuncho basin[2] and 110 kilometres (68 mi) away from the Pacific coast.[4] It is part of the Cordillera Ampato.[5]

Four main and ten total summits separated by broad saddles form the Coropuna massif which has an extent of 20 by 12 kilometres (12.4 mi × 7.5 mi) at 5,000 metres (16,000 ft) altitude.[6][7] Another description found six main summits in an ellipse.[8] The main summits are found in the western part and two are aligned in north-south direction with heights of 6,377 metres (20,922 ft) and 6,350 metres (20,830 ft). The eastern part features two summits, a central one has a ice-filled crater 6,234 metres (20,453 ft) and the easternmost one with 6,305 metres (20,686 ft) is the summit which has generated the most recent lava flows.[9] Cerro Cuncaicha forms a spur on eastern Coropuna's flank.[10] These summits have mostly smooth appearance with little aspect ratio.[11] The volcano is constructed from two phases, Coropuna I between 4,200–5,000 metres (13,800–16,400 ft) has a conical shape, other summits have grown up (Coropuna II) above it.[9] The terrain of Coropuna has moderate slopes rising from a basement of 4,600 metres (15,100 ft).[12] Erosion has incised deep gorges around Coropuna volcano.[9]

The origin of volcanism in the Andes is because the collision of the floor of the Pacific Ocean with the South America plate. This collision generates tectonic forces which lift blocks of the Central Andes up and create fissures along which magma can reach the surface.[13] Neighbouring volcanoes are 5,498 metres (18,038 ft) Nevado Firura (15°14′S 72°48′W / 15.233°S 72.800°W / -15.233; -72.800) and 6,093 metres (19,990 ft) Solimana (15°24′S 72°52′W / 15.400°S 72.867°W / -15.400; -72.867).[7] Firura is formed by a double dome, while Solimana features a caldera and a high, glacially affected topography.[14] Another volcano Ampato lies 85 kilometres (53 mi) southeast.[8]

Coropuna is part of the northern Central Volcanic Zone.[7] Coropuna is part of the main volcanic arc together with Ampato-Sabancaya-Hualca Hualca, Chachani and El Misti.[15] The Andes in this area are still growing and erosion has cut deep valleys into them.[6]

The bulk of the edifice is Quaternary. Activity began in the Miocene.[7] 5 million years ago the first latiandesites were erupted.[16] The minor eruptive centres Pumaranra and Antapuna are K-Ar dated 1.3 ± 0.11 and 1.02 ± 0.11 million years.[17] Much of the edifice is formed by lavas.[6]

Volcanic history and future threat

Coropuna is constructed on Tertiary ignimbrites that form the Puna,[4] one of which dated 14 mya.[16] Around the volcano these are completely buried. The dating of these ignimbrites is not entirely clear.[6] Beginning in the mid-Pliocene, the Coropuna I and Coropuna II edifices were constructed by large lava flows. Only planezes remain visible of Coropuna I.[18] Evidence in Majes valley indicates that volcanic activity frequently resulted in lahars when parts of the ice cap melted under the influence of volcanic activity.[19] Some explosive activity has thrown lava bombs up to 7 kilometres (4.3 mi) away.[20]

The bulk of the edifice was formed during the Pliocene and Pleistocene.[21] In the early Holocene, andesite lava flows overran late moraines.[7] Strong glacial and other erosion effects can be recognized on Coropuna.[8] Chlorine-36 exposure dating has found ages of 6,000 years ago for the western lava flow and 2,000 on the eastern lava flows.[22] These lava flows are tens of meters thick and 5–9 kilometres (3.1–5.6 mi) long and are only weakly eroded,[21] conserving most of their breccia cover.[23] Each of these lava emissions is associated with the formation of mudflows from lava-ice interaction.[24] The youngest date reported is 1,100 ± 100 years ago on one of these lava flows.[3]

Present day activity includes a chain of warm springs associated with the volcano.[25] An earthquake swarm and associated ground deformation were observed near Coropuna and Sabancaya in 2001.[26] Interaction between the ice cap and future eruptive activity is considered to be a hazard at Coropuna, especially in light of the extreme altitude differences that are found in the territory. Likewise, earthquakes could result in the collapse of part of the ice cap.[27] Several towns are located downstream of Coropuna, including Viraco, Machahuay, Salamanca, Chichas, Yanaquihua, Andaray and Punta Colorada.[28]

Petrology

Petrologically, dark coloured latiandesites form the bulk of the lavas. These contain plagioclase and quartz as well as smaller amounts of amphibole and biotite. Pyroxene and titanomagnetite are also found. The groundmass of Coropuna rocks contains plagioclase and pyroxene embedded in brown glass, the whole having a hyalophilic appearance. The magmas originated in a depth of 8–12 kilometres (5.0–7.5 mi).[29][30] Earlier latiandesites are more basic than the later ones.[16] Ignimbrites are rhyodacitic.[16]

Based on chemical and petrographic data formed from water-poor source material at depth, with phenocrysts forming at depths of less than 35 kilometres (22 mi).[31] Temperatures of Coropuna's eruption products are estimated at 700–1,200 metres (2,300–3,900 ft).[32] The magmas during their whole journey to the surface move over vertical distances of 70–120 kilometres (43–75 mi). During this ascent, secondary magmas are formed which generate evolved rocks.[33] Post-eruption, meltwater derived from the ice cap has caused hydrothermal alteration of the edifice.[21]

Ice cap

Ice thickness in 2010

The Coropuna glacier is located 155 kilometres (96 mi) northwest of Arequipa.[34] Solely exceeded by the Quelccaya Ice Cap it is the largest tropical ice cap.[35] The Coropuna ice cap has its highest point at 6,446 metres (21,148 ft) altitude.[34] The average thickness in a 2010 study was 80.8 ± 16.5 metres (265 ± 54 ft) and a total volume of 4.62 ± 0.94 cubic kilometres (1.11 ± 0.23 cu mi).[36] In 1962 at least 17 glaciers formed this ice cap.[5] Present day outlet glaciers reach down to 5,500–5,100 metres (18,000–16,700 ft) on the southern and northern side respectively.[14] The northeastern glaciers are smaller than the southeastern ones.[37] Beneath the glacier above 4,500 metres (14,800 ft) altitude gelifluction and other periglacial features form the terrain.[6]

Evidence of glaciation is present already in the oldest stages of Coropuna volcanic activity,[19] the mountain was at least glaciated since the Pliocene.[21] During the Last Glacial Maximum, Coropuna's longest glacier was the 12 kilometres (7.5 mi) long Quebrada Ullulo glacier. The LGM ice cap covered a surface area of at a minimum 365 square kilometres (141 sq mi). Outlet glaciers descended down to 4,540–3,780 metres (14,900–12,400 ft) altitude on the northern and southern flank respectively.[38] Equilibrium line altitudes ranged from 5,120–5,230 metres (16,800–17,160 ft) on the northern to 4,700–4,800 metres (15,400–15,700 ft) on the southern side. Aside from a north-south gradient, a possibly wind sublimation driven east-west gradient in equilibrium line altitudes is visible.[39] Apart from Ullulo on the northern flank, Huayllaura and Quipchane were other outlet glaciers on the southern, Pucunchiloyocc on the western and Cospanja on the eastern flank.[14] Based on Chlorine-36 accumulation data on moraines, between 20,000-16,000 years ago a major expansion and around 12,000-11,000 years ago a minor expansion occurred. A later minor expansion was found 9,000 years ago. On the southern flank, a major expansion took place 14,000 years ago and a minor one 10,000-9,000 years ago. A later minor expansion was found 6,000 years ago.[22] In the late Holocene, the snowline was found at 5,200–5,775 metres (17,060–18,947 ft) altitude.[40]

Coropuna's largest moraines were formed during the Last Glacial Maximum (LGM), ~25,000-20,000 years ago.[38] Gravel and boulders form the bulk of the LGM moraines.[38] There are several stages of moraines between these LGM moraines and the present day ones, some linked to the late 19th century advance and other more extensive ones late glacial advances. All these moraines are crisp and well preserved by the aridity.[14] The moraines 0.5 kilometres (0.31 mi) within the present day ice margin are steep sided.[10] The current retreat leaves terminal moraines which are small and poorly developed.[41]

Ice loss of Coropuna after 1995

In 1970 Coropuna's glaciers formed 4% of Peru's total glacier surface.[42] The Coropuna ice cap has shrunk between 1955 and 2008,[43] from 122.7 square kilometres (47.4 sq mi) to 48.1 square kilometres (18.6 sq mi) surface area.[44] This shrinkage by 1.4 square kilometres (0.54 sq mi) per year may result in the disappearance of the glacier by 2045.[45] Surface area as measured by satellite images decreased from 1975 (105 ± 16 square kilometres (40.5 ± 6.2 sq mi)) over 1986 (96 ± 15 square kilometres (37.1 ± 5.8 sq mi)) and 1996 (64 ± 8 square kilometres (24.7 ± 3.1 sq mi)) and 2003 (56 ± 6 square kilometres (21.6 ± 2.3 sq mi))[46] to 2007 (47 square kilometres (18 sq mi)).[37] Potentially, ice masses will disappear soon while others will persist for decades.[37] Further, the snowline has risen much higher than the glacier termini.[40] This retreat mirrors the retreat of most glaciers in the world since the end of the Little Ice Age.[42]

Coropuna is drained by the Rio Arma and Rio Majes rivers, both of which end in the Pacific Ocean.[5] During the dry season, Coropuna's glaciers are a major source of water in the region, and concern has been raised that its disappearance may result in water shortages just in a time where population growth has increased water consumption and created conflict about water distribution.[47] On the Coropuna glacier depend 30,000 people in one way or the other, 8,000 for water supply.[34] Already the Inca used the waters of Coropuna, with an irrigation system fetching waters from the glaciers from 5,600 metres (18,400 ft) altitude. It is the highest irrigation system in the world.[48]

Ice cores indicate that the Coropuna glacier receives mostly continental dust.[49] Ice core data indicate that 4,200 years ago there was a severe drought, while 5,200 years ago a wet and cold period occurred.[50] More recent data show a severe drought 1790-1796.[51] Fossil remains of rock glaciers have been found on the southeastern flank at altitudes 4,500–5,250 metres (14,760–17,220 ft).[52]

Climate and vegetation

Close to the ice, diurnal temperature variation dominates over seasonal effects.[5] Temperature has generally increased in the area (0.1 °C (32.2 °F) per decade since 1939), with El Nino events possibly playing a role.[53] Analysis of plankton in the Lake Titicaca indicates that a glacial climate was found until 10,000-9,000 years ago.[22]

Because of the rain shadow of the Andes and the temperature inversion over the Pacific, the climate is arid with precipitation of 390 millimetres (15 in) at 6,080 metres (19,950 ft) altitude.[7] Water cannot reach Coropuna from the Pacific Ocean.[27] Most precipitation (70-90%) falls during summer (December-March). A sharp reduction in precipitation was found during El Nino years 1982-1983 and 1992.[54] These El Nino events were also accompanied by lower cloud cover, higher temperatures and lower wind speed thus increasing the glacier surface loss.[46] However, the El Nino 1997/1998 was accompanied with large precipitation.[55] Precipitation mostly originates from the Atlantic Ocean via the Amazon basin.[56] Pollen data tend to be dominated by local species during dry spells. Occasionally strong southern cold outbreaks reach Coropuna's latitudes.[49] As evidenced by the Sajsi (25,000-19,000 years ago), Tauca (18,000-14,000 years ago) and Coipasa (13,000-11,000 years ago) lake highstands, ice age humidity was much higher in the Altiplano.[19]

Based on mapping, in 1955 the equilibrium line altitude had a mean elevation of 5,687 ± 49 metres (18,658 ± 161 ft) but has since then risen by 80–90 metres (260–300 ft).[39] As is the case farther south in Chile, the snowline altitude is chiefly governed by the precipitation and not by the temperature.[52]

Local plant species attested by pollen data are Asteroideae, Poaceae and Polylepis.[49] Vegetation ends at 5,000 metres (16,000 ft) altitude and is formed beneath this line by Azorella compacta and ichu grass.[14] The arid climate means that the flora is highly xerophilic.[57] A distinct peat bog and marsh vegetation is found in wetter parts of Coropuna's slopes. Polylepis woodlands are found on the southern slope.[58]

Religious and archeological importance

In Inca mythology, Coropuna was identified as an Apu. An Inca path leading up to the mountain has been found, including bones and pottery fragments up to 6,200 metres (20,300 ft) of altitude.[48] Over thirty archeological sites, many of them predating the Incas, have been found around Coropuna. The Inca sites are the highest ones but Inca sites are also found next to bogs such as Maucta Llacta.[59]

References

  1. ^ a b "Coropuna". Global Volcanism Program. Smithsonian Institution. 26 February 2016.
  2. ^ a b Bromley et al., 2011, p.305
  3. ^ a b Úbeda, Jose; Palacios, D.; Vázquez-Selem, Lorenzo. "La evolución glaciovolcánica del Nevado Coropuna desde la transición del Pleistoceno al Holoceno". researchgate.net (in Spanish). Lima, Peru: XVI Congreso Peruano de Geología. p. 4. Retrieved 26 February 2016.
  4. ^ a b Weibel et al., 1978, p.245
  5. ^ a b c d Silverio et al., 2012, p.5878
  6. ^ a b c d e Weibel et al., 1978, p.246
  7. ^ a b c d e f Bromley et al., 2011, p.306
  8. ^ a b c Bullard, Fred M. (December 1962). "Volcanoes of Southern Peru". Bulletin Volcanologique. 24 (1): 444. doi:10.1007/BF02599360.
  9. ^ a b c Jose Úbeda Palenque, El clima, la vegetación y la evolución volcánica y glaciar del Nevado Coropuna, p.1
  10. ^ a b Bromley et al., 2011, p.309
  11. ^ Peduzzi et al., 2009, p.840
  12. ^ Racoviteanu et al., 2007, p.112
  13. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.39
  14. ^ a b c d e Bromley et al., 2011, p.307
  15. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.66
  16. ^ a b c d Weibel et al., 1978, p.251
  17. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.165
  18. ^ Jose Úbeda Palenque, El clima, la vegetación y la evolución volcánica y glaciar del Nevado Coropuna, p.9
  19. ^ a b c Jose Úbeda Palenque, El clima, la vegetación y la evolución volcánica y glaciar del Nevado Coropuna, p.10
  20. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.95
  21. ^ a b c d Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.25
  22. ^ a b c Úbeda, J.; Palacios, D.; Vázquez-Selém, L. "Glacial and volcanic evolution on Nevado Coropuna (Tropical Andes) based on cosmogenic 36Cl surface exposure dating". The SAO/NASA Astrophysics Data System. EGU General Assembly 2012. Retrieved 26 February 2016.
  23. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.166
  24. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.112
  25. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.174
  26. ^ Jay, J.; Pritchard, M.E.; Aron, F.; Delgado, F.; Macedo, O.; Aguilar, V. "Volcano-tectonic interactions at Sabancaya and other Peruvian volcanoes revealed by InSAR and seismicity". The SAO/NASA Astrophysics Data System. American Geophysical Union, Fall Meeting 2013. Retrieved 26 February 2016.
  27. ^ a b Jose Úbeda Palenque, El clima, la vegetación y la evolución volcánica y glaciar del Nevado Coropuna, p.2
  28. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.29
  29. ^ Venturelli et al., 1978, pp.214-215
  30. ^ Weibel et al., 1978, p.248
  31. ^ Venturelli et al., 1978, pp.226
  32. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.114
  33. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.82
  34. ^ a b c Peduzzi et al., 2010, p.314
  35. ^ Ubeda Palenque, José (2011) El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna, (Cordillera Occidental de los Andes Centrales). p.24
  36. ^ Peduzzi et al., 2010, pp.320-321
  37. ^ a b c Úbeda, J.; Palacios, D.; Vázquez, L. "Reconstruction of Equilibrium Line Altitudes of Nevado Coropuna Glaciers (Southern Peru) from the Late Pleistocene to the present". The SAO/NASA Astrophysics Data System. EGU General Assembly 2009. Retrieved 26 February 2016.
  38. ^ a b c Bromley et al., 2011, p.308
  39. ^ a b Bromley et al., 2011, p.312
  40. ^ a b Bromley et al., 2011, p.313
  41. ^ Bromley et al., 2011, p.310
  42. ^ a b Silverio et al., 2012, p.5876
  43. ^ Peduzzi et al., 2010, p.313
  44. ^ Peduzzi et al., 2010, p.318
  45. ^ Peduzzi et al., 2010, p.322
  46. ^ a b Silverio et al., 2012, p.5882
  47. ^ Silverio et al., 2012, p.5877
  48. ^ a b Chávez Chávez, José Antonio (July 2001). "INVESTIGACIONES ARQUEOLÓGICAS DE ALTA MONTAÑA EN EL SUR DEL PERÚ". Chungará (Arica) (in Spanish). 33 (2). SciELO. doi:10.4067/S0717-73562001000200014. ISSN 0717-7356.
  49. ^ a b c Herreros et al., 2009, p.32
  50. ^ Thompson, L.G.; Mosley-Thompson, E.S.; Buffen, A.; Urmann, D.; Davis, M.E.; Lin, P. "Tropical Glaciers: Recorders and Indicators of Climate Change". The SAO/NASA Astrophysics Data System. American Geophysical Union, Fall Meeting 2008. Retrieved 26 February 2016.
  51. ^ Thompson, L.G.; Mosley-Thompson, E.S.; Davis, M.E.; Urmann, D.; Buffen, A. "Ice Core Evidence for Amplification of the Recent Warming at High Elevations in the Tropics and the Likely Regional Impacts". The SAO/NASA Astrophysics Data System. American Geophysical Union, Fall Meeting 2007. Retrieved 26 February 2016.
  52. ^ a b Dornbusch, U. (1 January 2005). "Glacier-rock glacier relationships as climatic indicators during the late Quaternary in the Cordillera Ampato, Western Cordillera of southern Peru". Geological Society, London, Special Publications. 242 (1): 77. doi:10.1144/GSL.SP.2005.242.01.07.
  53. ^ Silverio et al., 2012, p.5885
  54. ^ Herreros et al., 2009, p.28
  55. ^ Peduzzi et al., 2009, p.841
  56. ^ Herreros et al., 2009, p.33
  57. ^ Jose Úbeda Palenque, El clima, la vegetación y la evolución volcánica y glaciar del Nevado Coropuna, p.3
  58. ^ Kuentz, Adèle; de Mera, Antonio Galán; Ledru, Marie-Pierre; Thouret, Jean-Claude (October 2007). "Phytogeographical data and modern pollen rain of the puna belt in southern Peru (Nevado Coropuna, Western Cordillera)". Journal of Biogeography. 34 (10): 1768. doi:10.1111/j.1365-2699.2007.01728.x.
  59. ^ Kuentz, Adèle; Thouret, Jean-Claude; Ledru, Marie-Pierre; Forget, Marie-Émilie (1 August 2011). "Sociétés andines et changements environnementaux depuis 4 000 ans dans la région du Nevado Coropuna (sud du Pérou)". Bulletin de l’Institut français d’études andines (40 (2)): 235–257. doi:10.4000/bifea.1388.
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Sources

Books

  • Biggar, John (2005). The Andes: A Guide for Climbers (3rd ed.). Andes Publishing (Scotland). pp. 304 pp. ISBN 0-9536087-2-7.
  • González-Ferrán, Oscar (1995). Volcanes de Chile. Santiago, Chile: Instituto Geográfico Militar. pp. 640 pp. ISBN 956-202-054-1. (in Spanish; also includes volcanoes of Argentina, Bolivia, and Peru)
  • De Silva, Shanaka L.; Francis, Peter (1991). Volcanoes of the Central Andes. Springer-Verlag. pp. 216 pp. ISBN 3-540-53706-6.
  • "Coropuna". Global Volcanism Program. Smithsonian Institution.
  • Reinhard, Johan (1999). "Coropuna: Lost Mountain Temple of the Incas." South American Explorers Journal 58: 5, 26-30.
  • Reinhard, Johan (2005). The Ice Maiden: Inca Mummies, Mountain Gods, and Sacred Sites in the Andes. Washington, D.C.: National Geographic Society. ISBN 0-7922-6838-5.
  • Ziólkowski, Mariusz (2008). "Coropuna y Solimana: Los Oráculos de Condersuyos." In Adivinación y oráculos en le Mundo Andino Antiguo, Curatola, Marco and Mariusz Ziólkowski (eds.), pp. 121–159. Fundo Editorial de la Pontificia Universidad Católica del Perú, Lima.

See also

External links

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