Ubinas: Difference between revisions

Coordinates: 16°21′18″S 70°54′11″W / 16.355°S 70.903°W / -16.355; -70.903
From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Switching template
Transfer from userspace
(No difference)

Revision as of 15:38, 1 June 2018

Ubinas
Ubinas volcano and Lake Salinas, seen here in August 2015.
Highest point
Elevation5,672 m (18,609 ft)[1][2]
Coordinates16°21′18″S 70°54′11″W / 16.355°S 70.903°W / -16.355; -70.903[1]
Geography
Ubinas is located in Peru
Ubinas
Ubinas

Ubinas is an active 5,672-metre (18,609 ft) stratovolcano in the Andes of southern Peru. Until 2006, this stratovolcano had not erupted for about 40 years.

Name

Ubinas is also known as Uvillas or Uvinas.[1]

Geography and geomorphology

Ubinas is a 5,672 metres (18,609 ft) high[2] conical[3] volcano that rises 1.4 kilometres (0.87 mi) from a 65 square kilometres (25 sq mi) circular surface[4] at the margin of a high plateau.[5] An elevation gradient of about 2 kilometres (1.2 mi) distinguishes this high plateau from valleys southeast of Ubinas,[6] the Ubinas valley.[7] Some of the upper slopes of Ubinas have angles of up to 45 degrees.[1] The total volume of the volcano is estimated to be about 56 cubic kilometres (13 cu mi).[4] Glacial valleys, cirques and moraines down to elevations of 4,000 metres (13,000 ft) indicate that glaciers developed on Ubinas during the last glacial maximum.[8]

The summit of the volcano is cut by a 1.4 kilometres (0.87 mi) wide and 150 metres (490 ft) deep caldera[1] with an elliptical shape that was formed both by collapses and by explosive eruptions. The caldera walls are formed by lava flows bearing traces of hydrothermal alteration, while the caldera floor is covered by debris from explosive eruptions and lava flows.[9] It contains two[7] or one ash cone with a 400 metres (1,300 ft) wide and 300 metres (980 ft) deep triangle-shaped crater in its southern side.[6]

Hydrology and human geography

Acid springs have been identified in the crater, their waters capable of corroding silicon after a few hours' exposure. In the 1970s,[7] the crater had an ephemeral crater lake that appears after wet seasons.[1] Laguna Piscococha is located on the western foot of the volcano, while the Rio Para and Rio Sacuaya flow past its eastern and southern slopes respectively.[10] Other rivers on the slopes of Ubinas are the Quebrada Infiernillo on the southeastern, Rio Volcanmayo on the southern and Quebrada Postcone on the southwestern flank. Sacuaya then becomes the Rio Ubinas and after confluence with the Rio Para ends in the Rio Tambo;[11] the Rio Ubinas valley is densely inhabited.[12]

The towns of Querapi, Tonohaya, Ubinas and Viscachani lie south, southeast, southeast and northwest of the volcano, respectively;[10][13] in total there are about 5,000 people within 12 kilometres (7.5 mi) from the volcano.[12] Arequipa lies 60 kilometres (37 mi) west of the volcano.[4] Roads run along the northern and southern-southwestern foot of Ubinas,[10] the latter of which connects Ubinas with Arequipa.[13]

Geology

Off the western coast of South America, the Nazca Plate subducts beneath the South American Plate at a rate of 6–4 centimetres per year (2.4–1.6 in/year).[2] This subduction process is responsible for the formation of the Andes as well as the Altiplano-Puna, which took place within the last 25 million years, as well as for volcanism and earthquakes.[14]

Ubinas is part of the Peruvian Western Cordillera[5] and volcanically of the Central Volcanic Zone of the Andes.[2] The Central Volcanic Zone together with the Northern Volcanic Zone and the Southern Volcanic Zone is one out of three volcanic belts in the Andes.[7]

Peruvian volcanoes include both stratovolcanoes which are typically active for less than 500,000 years and long-lived clusters of lava domes. Historical eruptions have been recorded at seven volcanoes in Peru, El Misti, Huaynaputina, Sabancaya, Ticsani, Tutupaca, Ubinas and Yucamane, while Ampato, Casiri, Chachani, Coropuna and Sara Sara are dormant.[2] The 1600 eruption of Huaynaputina had an enormous impact, including a cold summer in the northern hemisphere.[15]

Ubinas is part of a group of volcanoes that extends in north-south direction[1] together with Ticsani and Huaynaputina. This group of volcanoes is characterized by its position behind the main volcanic arc and a common geochemical and tectonic signature,[14] the latter of which is reflected by the existence of a graben occupied by the Rio Tambo and whose marginal faults are the sites of the volcanic vents.[16] The magmas erupted by all three volcanoes appears to originate in a common magma chamber at 20–35 kilometres (12–22 mi) depth, with seismic activity along the margins of the chamber.[17] Aside from this deep reservoir, Ubinas also has a shallower magma chamber at 4–7 kilometres (2.5–4.3 mi) depth.[18]

The basement of Ubinas consists of volcanic rocks of different ages.[4] The oldest volcanic rocks of the Matalaque Volcanics are of Upper Cretaceous and crop out east and southeast of Ubinas, far away from the volcano. Most of the volcanics in proximity of Ubinas are the younger, Eocene-to-Oligocene Tacaza Group and the more restricted Miocene-Pliocene Barroso Group[9] which directly underlies the Ubinas edifice.[4] Even older basement rocks include Paleoproterozoic plutons and the sedimentary Yura Group of Jurassic-Cretaceous age.[14] A depression, whose margin is cut by landslide scars, cuts into the basement southeast of Ubinas[4] and may be the Ubinas valley.[7] Faults cut across the volcano and create unstable areas especially in its southern sector.[19]

A debris avalanche on the southeastern flank has reached a distance of 10 kilometres (6.2 mi) from the volcano[1] and has left a collapse scar that is drained by the Volcanmayo River.[9] This collapse took place early in the history of the volcano and removed a volume of about 2.8 cubic kilometres (0.67 cu mi) rocks from the volcano[20] and underlying basement.[21] Additional collapses have occurred during the Holocene, including one 1 cubic kilometre (0.24 cu mi) collapse that has left a hummocky deposit on the southern flank.[22] The sloping terrain that Ubinas is built on predisposes it to landsliding southward; future collapses in that direction are possible.[23]

Composition

Rocks on Ubinas have compositions ranging from basaltic andesite to rhyolite, with andesite and dacite being the dominant components of the volcano. The volcanic rocks define a potassium-rich calc-alkaline suite.[24] Assimilation of crustal material and fractional crystallization are involved in the genesis of this magma suite.[19]

There is a trend of more recent volcanic events producing more diverse rocks than the early eruptions,[25] probably owing to a change in the magma supply regime from steady before 25,000 years ago to more irregular after that time[26] with a generally higher magma supply.[27]

Eruptive history

The oldest pre-Ubinas volcanics crop out north and south of the volcano.[9] The volcano developed in two phases, Ubinas I and Ubinas II.[1] Most of the volcano developed in the middle and late Pleistocene.[4] Volcanic activity started after a change in regional tectonics, which may have triggered the formation of magma chambers.[28]

Ubinas I is represented by lava flows at the foot of the volcano and debris and ignimbrite deposits in the south and southeast of Ubinas, and it forms a 600 metres (2,000 ft) high shield.[9] It was later cut on its southern side by an older debris avalanche[20] that probably occurred over 376,000 years ago.[21] The last activity of Ubinas I formed over four units of pyroclastic flows with a total volume of about 1.8 cubic kilometres (0.43 cu mi) and possibly an old caldera before 261,000 ± 10,000 years ago.[29]

Ubinas II is steeper and rises 900 metres (3,000 ft) from above this shield.[9] It consists mainly of 20–40 metres (66–131 ft) thick lava flows but also several lava domes with accompanying block-and-ash flows, all of which were emplaced between 261,000 ± 10,000 and 142,000 ± 30,000 years ago. Afterwards, lack of volcanic outcrops suggests a period of dormancy lasting until 25,000 - 14,700 years ago during which glaciers grew on the volcano.[8]

25,000-21,000 volcanic activity restarted and led to the emplacement of ash flow and pumice layers as well as tephra from phreatomagmatic and explosive eruptions, with deposits having thicknesses of about 2–4 metres (6 ft 7 in – 13 ft 1 in) in many places.[8] The total volume of each eruption deposit ranges 1–2 cubic kilometres (0.24–0.48 cu mi) and they crop out as far as 35 kilometres (22 mi) from Ubinas.[22] It is likely that the summit caldera formed during this time period, before 9,700 years ago.[8]

After 7,500 years ago, volcanic activity has been characterized mainly by various kinds of explosive eruptions. These eruptions have expelled less than 0.1 cubic kilometres (0.024 cu mi) of material each time and left widespread deposits of ash, volcanic blocks and lapilli. A Plinian eruption occurred 980 ± 60 years before present and expelled 2.8 cubic kilometres (0.67 cu mi) of pumice and tephra, which has formed a deposit with five separate layers of pumice, ash and lapilli.[22]

The various explosive eruptions of Ubinas have deposited material as far as 15 kilometres (9.3 mi) away from the volcano.[30] Landslides also took place in this time, including the 1 cubic kilometre (0.24 cu mi) collapse before 3,670 ± 60 years before present.[22]

Historical

Ubinas is the most active volcano of Peru, with small explosive eruptions ongoing since the 16th century. Events are recorded from 1662, 1667, 1677, 1784, 1830, 1862, 1865, 1867, 1869, 1906, 1907, 1937, 1951, 1956 and 1969,[1] with an average eruption rate of one eruption every twenty to thirty-three years. These eruptions have damaged communities around the volcano and occasionally caused epidemics[30] and human and cattle fatalities from the ingestion of ash. The 1667 eruption was the largest in historical time, producing about 0.1 cubic kilometres (0.024 cu mi) of scoria.[13] In recent years eruptions have occurred in 2006, 2013-2016 and 2016-2017.[1]

2006 - 2007 eruption

The first episode of the 2006-2007 eruption sequence involved the ejection of large volcanic bombs at high speed and the emission of small quantities of ash.[31] Gas and ash columns were emitted between April and October of 2006 and reached heights of about 3–4 kilometres (1.9–2.5 mi).[32] Volcanically-induced melting of snow that had fallen on the summit during the 2006-2007 summer induced a mudflow in January 2007 that descended the Rio Ubinas valley.[33] Subsequently volcanic activity decreased again until late 2009[32] and consisted of degassing and of Vulcanian eruptions.[34] This eruption was probably triggered by the entry of fresh magma in the magma plumbing system and the subsequent interaction of ascending magmas with the hydrothermal system of Ubinas.[35]

Before the 2006 event, Ubinas despite is record of activity was essentially unmonitored, the inhabitants of the area largely unaware of volcanic hazards and there were no emergency plans for future eruptions available;[13] a "Scientific Committee" was formed on the 30th March 2006 to remedy these deficiencies.[36] A region of about 100 square kilometres (39 sq mi) was hit by the effects of the eruption:[6] The ash fall from the eruption caused health problems and disrupted pastures and agriculture in the region around the volcano, resulting in about 1,000,000 US dollars of damage[37] and the flight of local residents to Arequipa and Moquegua.[36] One village on the southern flank was temporarily evacuated to a location with shelters farther south from the volcano,[38] and a proposal to permanently resettle people from the high hazard areas around Ubinas is pending As of 2010.[39]

2013 - 2014 eruption

A new eruption period started on the 2nd September 2013 with a phreatic explosion, which was followed with more events in the subsequent few days. Strong but variable seismic activity, the observation of thermal anomalies in satellite images and the exhalation of gases characterized this eruption period. Lava effusion began in the summit crater in 2014 and increased after the 2014 Iquique earthquake, culminating in an explosive eruption on the 19th April 2014. Volcanic activity decreased afterwards until September 2014.[40]

Fumarolic activity

Aside from regular eruptions, there are fumarolic-seismic events such as in 1995-1996 when sulfur dioxide and water vapour emitted at temperatures of up to 440 °C (824 °F) formed clouds[30] that rose over 1 kilometre (0.62 mi) above the crater.[10]

Fumaroles have been active at the bottom of the inner crater,[9] with about five separate fumarole areas identified within the crater before the 2006 eruption. In 1997, a gas cloud from the fumaroles filled the entire caldera night.[7] The fumaroles along with the spontaneous potential of Ubinas indicate that the volcano hosts an active hydrothermal system[10] 1–3 kilometres (0.62–1.86 mi) below the caldera.[35] Hot springs are found on the southeastern slopes of Ubinas.[41]

Hazards

Hazards stemming from volcanic activity at Ubinas are mainly the fallout from explosive eruptions, lahars of different origins, large landslides that can generate debris flows and pyroclastic flows.[4] Small explosive eruptions are the most likely hazard at Ubinas, while large Plinian eruptions are considerably less likely.[27] The area of the cone itself is the area most likely to be affected by volcanic phenomena, while pyroclastic flows and lahars are a danger for the valleys that drain Ubinas in southeastern direction and landslides are hazardous for an area of the southern flank.[11] Large Plinian eruptions could have effects on the city of Arequipa.[4]

Hazard maps were created subsequent to the 2006 eruptive event to show the relative risk in various locations around the volcano,[42] which are then graded in a three-zone scheme with one high-risk, one intermediate-risk and one low-risk zone. In addition, a contingency map was created to lay out the procedures to follow in case of various eruption scenarios. Both maps were widely disseminated after publication to aid in the response to future eruptions.[43]

See also

References

  1. ^ a b c d e f g h i j k "Global Volcanism Program". Smithsonian Institution.
  2. ^ a b c d e Thouret et al. 2005, p. 558.
  3. ^ Lavallée et al. 2009, p. 256.
  4. ^ a b c d e f g h i Thouret et al. 2005, p. 559.
  5. ^ a b Rivera et al. 2014, p. 124.
  6. ^ a b c Coppola et al. 2015, p. 200.
  7. ^ a b c d e f Gonzales et al. 2014, p. 134.
  8. ^ a b c d Thouret et al. 2005, p. 565.
  9. ^ a b c d e f g Thouret et al. 2005, p. 560.
  10. ^ a b c d e Thouret et al. 2005, p. 568.
  11. ^ a b Thouret et al. 2005, p. 578.
  12. ^ a b Rivera et al. 2010, p. 19.
  13. ^ a b c d Rivera et al. 2010, p. 20.
  14. ^ a b c Lavallée et al. 2009, p. 255.
  15. ^ Lavallée et al. 2009, p. 257.
  16. ^ Lavallée et al. 2009, pp. 261–262.
  17. ^ Lavallée et al. 2009, p. 263.
  18. ^ Rivera et al. 2014, p. 136.
  19. ^ a b Thouret et al. 2005, p. 579.
  20. ^ a b Thouret et al. 2005, p. 563.
  21. ^ a b Thouret et al. 2005, p. 564.
  22. ^ a b c d Thouret et al. 2005, p. 566.
  23. ^ Gonzales et al. 2014, p. 143.
  24. ^ Thouret et al. 2005, p. 570.
  25. ^ Thouret et al. 2005, p. 575.
  26. ^ Thouret et al. 2005, p. 576.
  27. ^ a b Thouret et al. 2005, p. 577.
  28. ^ Lavallée et al. 2009, p. 262.
  29. ^ Thouret et al. 2005, pp. 564–565.
  30. ^ a b c Thouret et al. 2005, p. 567.
  31. ^ Rivera et al. 2010, p. 21.
  32. ^ a b Rivera et al. 2014, p. 123.
  33. ^ Rivera et al. 2010, p. 22.
  34. ^ Rivera et al. 2014, p. 127.
  35. ^ a b Rivera et al. 2014, p. 138.
  36. ^ a b Rivera et al. 2010, p. 27.
  37. ^ Rivera et al. 2010, p. 26.
  38. ^ Rivera et al. 2010, pp. 31–32.
  39. ^ Rivera et al. 2010, p. 33.
  40. ^ Coppola et al. 2015, p. 204.
  41. ^ Gonzales et al. 2014, p. 137.
  42. ^ Rivera et al. 2010, p. 29.
  43. ^ Rivera et al. 2010, p. 30.

Sources

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Ubinas&oldid=843952012"