Supervolcano

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For the docudrama, see Supervolcano (docudrama)
A computer generated image of the supervolcanic Yellowstone Caldera erupting.
A computer generated image of the supervolcanic Yellowstone Caldera erupting.

A supervolcano or super volcanic eruption is a volcanic eruption which is orders of magnitude greater than any volcano in historic times, sufficient to cause long-lasting change to weather, threaten the extinction of species, and cover huge areas with lava and ash.

The term was originally used in the BBC popular science program, Horizon, in 2000 to refer to these types of eruption.[1][2] That programme introduced the subject to the 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 7 or 8 as "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: massive eruptions.

Contents

[edit] Large Igneous Provinces

Main article: Large igneous province

A large igneous province (LIP) e.g. Iceland, the Siberian Traps, Deccan Traps, 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 km2 and have volumes on the order of millions km3. 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 Mya. Research continues into the effect of the outpourings and whether they impacted upon 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 1783-1784 from the Laki fissure which is ~40 km long. An estimated 14 km3of basaltic lava was poured out during the eruption.

The Ontong Java Plateau has an area of about 2 million km2 .

[edit] Massive eruptions

Eruptions with a Volcanic Explosivity Index of 8 (VEI-8) are colossal events that throw out at least 1,000 km 3 Dense Rock Equivalent (DRE) of ejecta; VEI-7 events eject at least 100 km 3 (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)[3] its geology and volcanic succession has recently been re-analysed in the light of new discoveries.[4] 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 km 3, and both Mount Pinatubo in 1991 and Krakatoa in 1883 were VEI-6 with 25 km 3.

[edit] Known super eruptions

Satellite image of Lake Toba.
Satellite image of Lake Toba.

VEI-8 volcanic events have included eruptions at the following locations. Estimates of the volume of ejected material are given in parentheses.

The Lake Toba eruption plunged the Earth into a volcanic winter, eradicating an estimated 60%[5][6][7][8][9] of the human population (although humans managed to survive, even in the vicinity of the volcano[10]), and was responsible for the formation of sulfuric acid in the atmosphere.

VEI-7 volcanic events, less colossal but still supermassive, have occurred in the geological past. The only one in historic times is Tambora, in 1815.

For large flood basalt eruptions, see large igneous province.

[edit] 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 caused a phenomenon known as the Millennial Ice Age that lasted for ~1000 years and killed an estimated 60 to 75%[12][13][14][15][16] of the human population of the time.

An eruption of the Yellowstone supervolcano was originally one of the scenarios depicted in the docu-drama End Day, but was excluded from all transmissions to date for unknown reasons and is only presently mentioned at the show's BBC website (dead as of May 18, 2007; Internet Archive version).

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.[17]

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

In the Stargate Atlantis episode Inferno, the main characters are caught in the eruption of a supervolcano and escape using an Ancient warship.

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.

[edit] See also

[edit] References

  1. ^ BBC TV Horizon, 3 February 2000, Supervolcanoes
  2. ^ USGS Cascades Volcano Observatory
  3. ^ 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.
  4. ^ Kokelaar, B. P and Moore, I. D; 2006. Glencoe caldera volcano, Scotland. British Geological Survey, Keyworth, Nottingham. ISBN 0852725252.
  5. ^ Stanley H. Ambrose, University of Illinois at Urbana-Champaign, 1998
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.
  10. ^ Michael Petraglia et al., Science v.317, p.114 (2007)
  11. ^ Ashfall Fossil Beds State Historical Park. The Ashfall Story. Retrieved on 2006-08-08.
  12. ^ Stanley H. Ambrose, University of Illinois at Urbana-Champaign, 1998
  13. ^ 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.
  14. ^ 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.
  15. ^ 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.
  16. ^ 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.
  17. ^ Mystery of the Megavolcano official site, PBS.org

[edit] Sources

  • Ben G. Mason; David M. Pyle, and Clive Oppenheimer (2004). "The size and frequency of the largest explosive eruptions on Earth" (PDF). Bulletin of Volcanology 66 (8): 735-748. doi:10.1007/s00445-004-0355-9. 

[edit] External links