Supervolcano


Supervolcano

A supervolcano is a volcano capable of producing a volcanic eruption with an ejecta volume greater than 1,000 cubic kilometers (240 cubic miles). This is thousands of times larger than most historic volcanic eruptions.[1] Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is unable to break through the crust. Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. They can also form at convergent plate boundaries (for example, Toba) and continental hotspot locations (for example, Yellowstone).

The Discovery Channel highlighted six known supervolcanoes:[2] Yellowstone, Long Valley, and Valles Caldera in the United States; Lake Toba, North Sumatra, Indonesia; Taupo Volcano, North Island, New Zealand; and Aira Caldera, Kagoshima Prefecture, Kyūshū, Japan. Although there are only a handful of Quaternary supervolcanoes, supervolcanic eruptions typically cover huge areas with lava and volcanic ash and cause a long-lasting change to weather (such as the triggering of a small ice age) sufficient to threaten species with extinction.

Contents

Terminology

The term "supervolcano" was originally used in the BBC popular science television program Horizon in 2000 to refer to eruptions of this type.[3][4] That program introduced the subject of large-scale volcanic eruptions to the general public.

Volcanologists and geologists do not refer to "supervolcanoes" in their scientific work, since this is a blanket term that can be applied to a number of different geothermal conditions. Since 2003, however, the term has been used by professionals when presenting to the public. The term megacaldera is sometimes used for calderas with supervolcano characteristics, such as the Blake River Megacaldera Complex in the Abitibi greenstone belt of Ontario and Quebec, Canada. Eruptions that rate VEI 8 are termed "super eruptions".

Though there is no well-defined minimum explosive size for a "supervolcano", there are at least two types of volcanic eruption that have been identified as supervolcanoes: large igneous provinces and massive eruptions.

Large igneous provinces

Large igneous provinces (LIP) such as Iceland, the Siberian Traps, Deccan Traps, and the Ontong Java Plateau are extensive regions of basalts on a continental scale resulting from flood basalt eruptions. When created, these regions often occupy several thousand square kilometres and have volumes on the order of millions of cubic kilometers. In most cases, the lavas are normally laid down over several million years. They do release massive amounts of gases. The Réunion hotspot produced the Deccan Traps about 65 million years ago, coincident with the extinction of the dinosaurs at the end of the Cretaceous. Because the largest flood basalt event (the Siberian Traps) occurred around 250 Ma and was coincident with the largest mass extinction in history (end Permian), and the second largest flood basalt event (The Deccan Traps) occurred around 65 Ma and was coincident with the second largest extinction event (end Cretaceous), research continues into the effect of these volcanic outpourings and whether they contributed to mass extinctions.

Such outpourings are not explosive though fire fountains may occur. Many volcanologists consider that Iceland may be a LIP that is currently being formed. The last major outpouring occurred in 1783–84 from the Laki fissure which is ~40 km long. An estimated 14 km3 of basaltic lava was poured out during the eruption.

The Ontong Java Plateau now has an area of about 2 million km2, and the province was at least 50% larger before the Manihiki and Hikurangi Plateaus broke away.

Massive explosive eruptions

Eruptions with a Volcanic Explosivity Index (VEI) of 8 are colossal events that throw out at least 1,000 km3 Dense Rock Equivalent (DRE) of ejecta; VEI-7 events eject at least 100 km3 (DRE).

VEI-7 or 8 eruptions are so powerful that they often form circular calderas rather than cones because the downward withdrawal of magma causes the overlying mass to collapse and fill the void magma chamber beneath.

One of the classic calderas is at Glen Coe in the Grampian Mountains of Scotland. First described by Clough et al. (1909)[5] its geology and volcanic succession have recently been re-analysed in the light of new discoveries.[6] There is an accompanying 1:25000 solid geology map.

By way of comparison, the 1980 Mount St. Helens eruption was at the lower end of VEI-5 with 1.2 km3, and both Mount Pinatubo in 1991 and Krakatoa in 1883 were VEI-6 with 10 km3 and 25 km3. respectively.

Known super eruptions

Location of Yellowstone Hotspot in Millions of Years Ago

Estimates of the volume of ejected material are given in parentheses.

VEI 8

VEI 8 eruptions have happened in the following locations.

The Lake Toba eruption plunged the Earth into a volcanic winter, eradicating an estimated 60%[11][12][13][14][15] of the human population (although humans managed to survive even in the vicinity of the volcano[16]). However the coincidental agreement in above sources about percentage value of extinction is contrary to differing estimates of human population size at that time.[citation needed]

VEI 7

Cross-section through Long Valley Caldera

VEI-7 volcanic events, less colossal but still supermassive, have occurred in the geological past. The only ones in historic times are Tambora, in 1815, Lake Taupo (Hatepe), around 180 CE,[17] and possibly Baekdu Mountain, 969 CE (± 20 years).[18]

Ongoing studies

Media portrayal

Satellite image of Lake Toba, the site of a VEI-8 eruption ~75,000 years ago
Volcano, lake, and caldera locations in the Taupo Volcanic Zone
  • Nova featured an episode "Mystery of the Megavolcano" in September 2006 examining such eruptions in the last 100,000 years.[32]
  • In the episode "Humanity" of Young Justice, the Team must relieve the pressure of the Yellowstone Caldera Supervolcano caused by Red Volcano before an eruption with the potential for mass extinction takes place.

See also

Spaccato vulcano.png Volcanoes portal

Notes

  1. ^ http://volcanoes.usgs.gov/yvo/about/faq/faqsupervolcano.php#supervolcano
  2. ^ O'Hanlon, Larry. "Supervolcano: Yellowstone's Super Sisters". Discovery Channel. http://dsc.discovery.com/convergence/supervolcano/others/others.html. Retrieved 30 September 2009. 
  3. ^ BBC TV Horizon, 3 February 2000, Supervolcanoes
  4. ^ USGS Cascades Volcano Observatory
  5. ^ Clough, C. T; Maufe, H. B. & Bailey, E. B; 1909. The cauldron subsidence of Glen Coe, and the Associated Igneous Phenomena. Quart. Journ. Geol. Soc. 65, 611-678.
  6. ^ Kokelaar, B. P and Moore, I. D; 2006. Glencoe caldera volcano, Scotland. British Geological Survey, Keyworth, Nottingham. ISBN 0852725256.
  7. ^ Froggatt, P. C.; Nelson, C. S.; Carter, L.; Griggs, G.; Black, K. P. (13 February 1986). "An exceptionally large late Quaternary eruption from New Zealand". Nature 319 (6054): 578–582. doi:10.1038/319578a0. "The minimum total volume of tephra is 1,200 km³ but probably nearer 2,000 km³, ..." .
  8. ^ a b c http://www.volcano.si.edu/world/largeeruptions.cfm
  9. ^ Lindsay, J. M.; de Silva, S.; Trumbull, R.; Emmermann, R.; Wemmer, K. (2001). "La Pacana caldera, N. Chile: a re-evaluation of the stratigraphy and volcanology of one of the world's largest resurgent calderas". Journal of Volcanology and Geothermal Research 106 (1-2): 145–173. doi:10.1016/S0377-0273(00)00270-5. 
  10. ^ a b c http://bulletin.geoscienceworld.org/cgi/content/abstract/117/3-4/288 Lisa A. Morgan and William C. McIntosh, Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA, GSA Bulletin; March 2005; v. 117; no. 3-4; p. 288-306; DOI: 10.1130/B25519.1
  11. ^ Stanley H. Ambrose, University of Illinois at Urbana-Champaign, 1998
  12. ^ Knight, M.D., Walker, G.P.L., Ellwood, B.B., and Diehl, J.F., 1986, Stratigraphy, paleomagnetism, and magnetic fabric of the Toba Tuffs: Constraints on their sources and eruptive styles: Journal of Geophysical Research, v. 91, p. 10,355-10,382.
  13. ^ Ninkovich, D., Sparks, R.S.J., and Ledbetter, M.T., 1978, The exceptional magnitude and intensity of the Toba eruption, Sumatra: An example of using deep-sea tephra layers as a geological tool: Bulletin Volcanologique, v. 41, p. 286-298.
  14. ^ Rose, W.I., and Chesner, C.A., 1987, Dispersal of ash in the great Toba eruption, 75 ka: Geology, v. 15, p. 913-917. Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.
  15. ^ Williams, M.A.J., and Royce, K., 1982, Quaternary geology of the Middle Son Valley, north central India: Implications for prehistoric archaeology: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 38, p. 139-162.
  16. ^ Michael Petraglia et al., Science v.317, p.114 (2007)
  17. ^ a b Wilson, C. J. N.; Ambraseys, N. N.; Bradley, J.; Walker, G. P. L. (1980). "A new date for the Taupo eruption, New Zealand". Nature 288 (5788): 252–253. doi:10.1038/288252a0. http://www.nature.com/nature/journal/v288/n5788/abs/288252a0.html. 
  18. ^ Horn, Susanne; Schmincke, Hans-Ulrich (2000). "Volatile emission during the eruption of Baitoushan Volcano (China/North Korea) ca. 969 CE". Bulletin of Volcanology 61 (8): 537–555. doi:10.1007/s004450050004. "The 969±20 CE Plinian eruption of Baitoushan Volcano (China/North Korea) produced a total tephra volume of 96±19 km³ [magma volume (DRE): 24±5 km³]." 
  19. ^ Latter, J. H.; Lloyd, E. F.; Smith, I. E. M.; Nathan, S. (1992). Volcanic hazards in the Kermadec Islands and at submarine volcanoes between southern Tonga and New Zealand, Volcanic hazards information series 4. Wellington, New Zealand. Ministry of Civil Defence. 44 p.
  20. ^ "Macauley Island". Global Volcanism Program, Smithsonian Institution. http://www.volcano.si.edu/world/volcano.cfm?vnum=0402-021. 
  21. ^ Froggatt, P. C. and Lowe, D. J. (1990). A review of late Quaternary silicic and some other tephra formations from New Zealand: their stratigraphy, nomenclature, distribution, volume, and age, New Zealand Journal of Geology and Geophysics, 33, 89-109.
  22. ^ I. A. Nairn; C. P. Wood and R. A. Bailey (December 1994). "The Reporoa Caldera, Taupo Volcanic Zone: source of the Kaingaroa Ignimbrites". Bulletin of Volcanology 56 (6): 529–537. Bibcode 1994BVol...56..529N. doi:10.1007/BF00302833. http://www.springerlink.com/content/mu1970l8163tp006. Retrieved 2010-09-16. 
  23. ^ Karl D. Spinks, J.W. Cole, & G.S. Leonard (2004). Caldera Volcanism in the Taupo Volcanic Zone. In: Manville, V.R. (ed.) Geological Society of New Zealand/New Zealand Geophysical Society/26th New Zealand Geothermal Workshop, 6th–9th December 2004, Taupo: field trip guides. Geological Society of New Zealand miscellaneous publication 117B.
  24. ^ Bailey, R. A. and Carr, R. G. (1994). Physical geology and eruptive history of the Matahina Ignimbrite, Taupo Volcanic Zone, North Island, New Zealand, New Zealand Journal of Geology and Geophysics, 37, 319-344.
  25. ^ Izett, Glen A. (1981). "Volcanic Ash Beds: Recorders of Upper Cenozoic Silicic Pyroclastic Volcanism in the Western United States". Journal of Geophysical Research 86 (B11): 10200–10222. Bibcode 1981JGR....8610200I. doi:10.1029/JB086iB11p10200. 
  26. ^ Briggs, R.M.; Gifford, M.G.; Moyle, A.R.; Taylor, S.R.; Normaff, M.D.; Houghton, B.F.; and Wilson, C.J.N. (1993). "Geochemical zoning and eruptive mixing in ignimbrites from Mangakino volcano, Taupe Volcanic Zone, New Zealand". Journal of Volcanology and Geothermal Research 56: 175–203. doi:10.1016/0377-0273(93)90016-K. .
  27. ^ Shipley, Niccole; Bindeman, Ilya; Leonov, Vladimir (2009). "Petrologic and Isotopic Investigation of Rhyolites from Karymshina Caldera, the Largest "Super"caldera in Kamchatka, Russia". http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_162281.htm. 
  28. ^ Ort, M. H.; de Silva, S.; Jiminez, N.; Salisbury, M.; Jicha, B. R. and Singer, B. S. (2009). Two new supereruptions in the Altiplano-Puna Volcanic Complex of the Central Andes.
  29. ^ Ashfall Fossil Beds State Historical Park. "The Ashfall Story". http://www.ashfall.unl.edu/ashfallstory.html. Retrieved 2006-08-08. 
  30. ^ Lambert, Maurice B. (1978). Volcanoes. North Vancouver, British Columbia: Energy, Mines and Resources Canada. ISBN 0-88894-227-3. 
  31. ^ Liubov Vitaliena Golovanova; Vladimir Borisovich Doronichev; Naomi Elancia Cleghorn; Marianna Alekseevna Koulkova; Tatiana Valentinovna Sapelko; M. Steven Shackley (2010; 51 (5): 655). "Volcanoes Wiped out Neanderthals, New Study Suggests" (news release). ScienceDaily. Journal Current Anthropology (University of Chicago Press Journals). doi:10.1086/656185. http://www.sciencedaily.com/releases/2010/10/101006094057.htm. "Significance of Ecological Factors in the Middle to Upper Paleolithic Transition" 
  32. ^ Mystery of the Megavolcano website by PBS

References

External links


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