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Supervolcano

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For the docudrama, see Supervolcano (docudrama).

A supervolcano is a volcano capable of producing a volcanic eruption with ejecta 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] the 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 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 the extinction of species.

Terminology

The term "supervolcano" was originally used in the BBC popular science television program Horizon in 2000 to refer to these types of eruptions.[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 terms that can be applied to 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.[citation needed]


Large igneous provinces

Main article: Large igneous province

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 kilometres. 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. Research continues into the effect of the outpourings and whether they contributed to the extinction of the dinosaurs at the end of the Cretaceous.

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

See also: World's largest eruptions

Eruptions with a Volcanic Explosivity Index of 8 (VEI-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 has 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 25 km3.

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.

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]

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
  • A National Geographic Channel documentary called Earth Shocks portrayed the destructive impact of the rapid eruption at Lake Toba approximately 75,000 years ago, which is thought to have caused a phenomenon known as the Millennial Ice Age that lasted for about 1,000 years and killed an estimated 60–75%[11][12][13][15][14] of the human population of the time. But according to Alan Robock et al.,[28] the Toba incident did not initiate an ice age, but rather exacerbated an ice age that had already been underway. Nevertheless, the climate recovered over a few decades.
  • In 2005, an eruption of the Yellowstone supervolcano is one of the scenarios depicted in the docudrama End Day.[29]
  • In 2005, a two-part television docudrama called Supervolcano aired on BBC One, the Discovery Channel, and other television networks worldwide. It looked at the events that could take place if the Yellowstone supervolcano erupted. It featured footage of volcano eruptions from around the world and computer-generated imagery depicting the event. According to the program, such an eruption would have devastating effect across the globe and would cover virtually all of the United States with at least 1 cm of volcanic ash, causing mass destruction in the nearby vicinity and killing plants and wildlife across the continent. The dramatic elements in the program were followed by Supervolcano: The Truth About Yellowstone, a documentary about the evidence behind the film. The program had originally been scheduled to be transmitted in early 2005, but it was felt that this would be insensitive so soon after the 2004 Indian Ocean tsunami. The program and its accompanying documentaries were released on DVD region 2 simultaneously with its broadcast.[citation needed]
  • Nova featured an episode "Mystery of the Megavolcano" in September 2006 examining such eruptions in the last 100,000 years.[30]
  • In 2008, the Yellowstone supervolcano was featured in the BBC program 10 Things You Didn't Know About Volcanoes, presented by Dr. Iain Stewart, a volcanologist.

See also

Notes

  1. ^ http://volcanoes.usgs.gov/yvo/about/faq/faqsupervolcano.php#supervolcano
  2. ^ O'Hanlon, Larry. "Supervolcano: Yellowstone's Super Sisters". Discovery Channel. 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. (13 February 1986). "An exceptionally large late Quaternary eruption from New Zealand". Nature. 319: 578–582. doi:10.1038/319578a0. The minimum total volume of tephra is 1,200 km³ but probably nearer 2,000 km³, ... {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help).
  8. ^ a b c http://www.volcano.si.edu/world/largeeruptions.cfm
  9. ^ Lindsay, J. M.;de Silva, S.;Trumbull, R.; Emmermann, R. and 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. ^ a b Stanley H. Ambrose, University of Illinois at Urbana-Champaign, 1998
  12. ^ a b 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. ^ a b 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. ^ a b 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. ^ a b 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: 252–253. doi:10.1038/288252a0.
  18. ^ Horn, Susanne (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]. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  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.
  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. ^ 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.
  23. ^ Bailet, 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.
  24. ^ 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. doi:10.1029/JB086iB11p10200. {{cite journal}}: Cite has empty unknown parameters: |month= and |coauthors= (help)
  25. ^ Briggs, R.M. (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. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help).
  26. ^ 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.
  27. ^ Ashfall Fossil Beds State Historical Park. "The Ashfall Story". Retrieved 2006-08-08.
  28. ^ Robock, A., C.M. Ammann, L. Oman, D. Shindell, S. Levis, and G. Stenchikov (2009). "Did the Toba volcanic eruption of ~74k BP produce widespread glaciation?". Journal of Geophysical Research. 114: D10107. doi:10.1029/2008JD011652.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  29. ^ End Day website by the BBC
  30. ^ Mystery of the Megavolcano website by PBS

References

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