A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruptions on earth. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma is immense enough to radically alter the landscape and severely impact global climate for years, with a cataclysmic effect on life.
The term was originally coined by the producers of the BBC popular science programme, Horizon, in 2000 to refer to these types of eruptions. It is not a technical term used in volcanology. Though there is no well-defined minimum size for a "supervolcano", there are at least two types of volcanic eruption that have been identified as supervolcanoes. That investigation brought the subject more into the public eye, leading to further studies of the possible effects.
A two-part television docudrama entitled Supervolcano was shown on BBC ONE on 13 March 2005 and 14 March 2005 in Britain, the Discovery Channel on 10 April 2005 and 11 April 2005 in the United States, and ABC on 14 March 2005 and 27 March 2005 in Australia. It looked at the events that would take place if the Yellowstone supervolcano erupted and featured footage of volcano eruptions from around the world and computer-generated imagery to depict the event. According to the programme the eruption 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 showings were followed on BBC TWO in Britain and on the Discovery Channel in the United States by Supervolcano: The Truth About Yellowstone, one or two documentaries about the evidence behind the movie.
The programme had originally been scheduled for the new year, but it was felt that this would be insensitive so soon after the real-life tragedy of the 2004 Indian Ocean earthquake.
The programme and its accompanying documentaries were released on Region 2 DVD simultaneously with its broadcast.
Eruptions
Volcanic Explosivity Index-8 eruptions (VEI-8 for short) are mega-colossal events that extrude at least 1000 km³ of magma and pyroclastic material. Such an eruption erases virtually all life in a radius of hundreds of kilometers from the site, and entire continental regions further out can be buried meters deep in ash. VEI-8 eruptions are not so great as to form mountains, but instead circular calderas, resulting from the downward collapse of land at the eruption site to fill emptied space in the magma chamber beneath. The caldera can remain for millions of years after all volcanic activity at the site has died.
VEI-8 volcanic events have included eruptions at the following:
-
Aira Caldera, Kyūshū, Japan
-
Aso, Kyūshū, Japan
-
Campi Flegrei, Campania, Italy
-
Kikai Caldera, Ryūkyū Islands, Japan
-
Long Valley Caldera, California, United States
-
Lake Taupo, North Island, New Zealand
-
Lake Toba, Sumatra, Indonesia
-
Valle Grande, New Mexico, United States
-
Yellowstone Caldera, Wyoming, United States
The most recent eruption was at Lake Toba, Sumatra, and occurred around 74,000 years ago, plunging the Earth into a volcanic winter.
Basaltic flood
Basaltic floods are unexplosive volcanic eruptions that extrude enormous quantities of basaltic lava flat and deep over large areas, even covering entire sections of continent. Though not explosive, the gases and dust released by such an eruption impact global climate as much as a VEI-8, hence a supervolcano. Prehistoric basaltic floods have been suspected as causes or contributors to mass extinctions in the past, including the ultra-massive Permian extinction, which killed the majority of all then-living species, and the more famous but smaller Cretaceous extinction that extinguished most of the dinosaurs. Basaltic flood events have included eruptions at:
The two largest basaltic flood events in historic time have been at Eldgjá and Lakagigar, both in Iceland. Neither of these had an impact great enough to be considered supervolcanic events.
See also
External links
Last updated: 05-07-2005 16:56:29
Last updated: 05-13-2005 07:56:04
