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Supervolcano

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For the docudrama, see Supervolcano (docudrama).

A supervolcano or super volcanic eruption is a volcanic eruption which is substantially larger than any volcano in historic times (generally accepted to be greater than 1,000 cubic kilometers).[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). Supervolcanoes are relatively new to science.

Although there are only a handful of supervolcanoes, super volcanic 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.

Word origin

The term was originally used in the BBC popular science television programme Horizon in 2000 to refer to these types of eruptions.[2][3] That programme introduced the subject of large-scale volcanic eruptions to the general public.

Volcanologists and geologists do not refer to "super volcanoes" or "megacalderas" in their scientific work, but sometimes do in public presentations. However, they do describe eruptions that rate VEI 8 as "super eruptions".

  • Until 2003, supervolcano was not a technical term used in volcanology. The term megacaldera is sometimes used for caldera supervolcanoes, such as the Blake River Megacaldera Complex in the Abitibi greenstone belt of Ontario and Quebec, Canada.
  • 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.
  • Supervolcanoes were seen on other planets via the Voyager program craft on the moons of Jupiter and Saturn. However, this kind of volcano on earth was not discovered until long after the Voyager had gone on to their interplanetary missions. The outer Solar System volcanoes were mostly cryovolcanoes, not magma .

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

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)[4] its geology and volcanic succession has recently been re-analysed in the light of new discoveries.[5] 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

 
Satellite image of Lake Toba, the site of a VEI-8 eruption ~75,000 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%[9][10][11][12][13] of the human population (although humans managed to survive, even in the vicinity of the volcano[14]), and was responsible for the formation of sulfuric acid[citation needed] in the atmosphere. 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 AD,[15] and possibly Baekdu Mountain, around 979 AD.[16]

Media portrayal

A National Geographic 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 ~1000 years and killed an estimated 60 to 75%[19][20][21][22][23] of the human population of the time.

An eruption of the Yellowstone supervolcano is one of the scenarios depicted in the docu-drama End Day, BBC website.

In 2005 a two-part television docudrama entitled Supervolcano was shown on BBC, 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 movie. 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. Nova featured an episode Mystery of the Megavolcano, examining such eruptions in the last 100,000 years.[24]

In 2006 the Sci Fi Channel aired the documentary Countdown to Doomsday which featured a segment called "Supervolcano".

In 2006 ABC News aired the documentary Last Days on Earth which featured a segment called "Supervolcano".

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.

In the film 2012, an eruption of Yellowstone is one of several cataclysmic events which brings about the end of the world.

See also

References

  1. ^ http://volcanoes.usgs.gov/yvo/about/faq/faqsupervolcano.php#supervolcano
  2. ^ BBC TV Horizon, 3 February 2000, Supervolcanoes
  3. ^ USGS Cascades Volcano Observatory
  4. ^ 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.
  5. ^ Kokelaar, B. P and Moore, I. D; 2006. Glencoe caldera volcano, Scotland. British Geological Survey, Keyworth, Nottingham. ISBN 0852725256.
  6. ^ Froggatt, P. C. (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); Unknown parameter |day= ignored (help); Unknown parameter |month= ignored (help).
  7. ^ Jin, Y. G. (2000). "Pattern of Marine Mass Extinction Near the Permian-Triassic Boundary in South China". Science. 289: 432. doi:10.1126/science.289.5478.432.
  8. ^ Mundil, R; Ludwig, Kr; Metcalfe, I; Renne, Pr (2004). "Age and timing of the Permian mass extinctions: U/Pb dating of closed-system zircons". Science (New York, N.Y.). 305 (5691): 1760–3. doi:10.1126/science.1101012. ISSN 0036-8075. PMID 15375264. Uranium-lead dating {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  9. ^ Stanley H. Ambrose, University of Illinois at Urbana-Champaign, 1998
  10. ^ 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.
  11. ^ 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.
  12. ^ 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.
  13. ^ 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.
  14. ^ Michael Petraglia et al., Science v.317, p.114 (2007)
  15. ^ 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.
  16. ^ Horn, Susanne (2000). "Volatile emission during the eruption of Baitoushan Volcano (China/North Korea) ca. 969 AD". Bulletin of Volcanology. 61 (8): 537–555. doi:10.1007/s004450050004. The 969±20 AD 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}}: Cite has empty unknown parameter: |month= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  17. ^ 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).
  18. ^ Ashfall Fossil Beds State Historical Park. "The Ashfall Story". Retrieved 2006-08-08.
  19. ^ Stanley H. Ambrose, University of Illinois at Urbana-Champaign, 1998
  20. ^ 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.
  21. ^ 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.
  22. ^ Rose, W.I., and Chesner, C.A., 1987, Dispersal of ash in the great Toga 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.
  23. ^ 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.
  24. ^ Mystery of the Megavolcano official site, PBS.org

Sources

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