Supervolcano
From Open Encyclopedia
A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruption on Earth. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma is 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 program, Horizon, in 2000 to refer to these types of eruption. That investigation brought the subject more into the public eye, leading to further studies of the possible effects. At first, supervolcano was not a technical term used in volcanology, but more recently, in 2003 and 2004, the term has been used in articles. 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: massive eruptions and large igneous provinces.
A two-part television docudrama entitled Supervolcano was shown on BBC, the Discovery Channel, and other TV networks worldwide. It looked at the events that would take place if the Yellowstone supervolcano (the largest supervolcano on Earth according to the program) erupted. It featured footage of volcano eruptions from around the world and computer-generated imagery depicting the event. According to the program, 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 by Supervolcano: The Truth About Yellowstone, a documentary about the evidence behind the movie. The program had originally been scheduled to be aired in early 2005, but it was felt that this would be insensitive so soon after the real-life tragedy of the 2004 Indian Ocean earthquake. The program and its accompanying documentaries were released on DVD region 2 simultaneously with its broadcast.
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Massive eruptions
Eruptions with a Volcanic Explosivity Index of 8 (VEI-8) are mega-colossal events that extrude at least 1000 km³ of magma and pyroclastic material. Such an eruption would erase virtually all life within 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 so powerful that they form circular calderas rather than mountains because the downward collapse of land at the eruption site fills emptied space in the magma chamber beneath. The caldera can remain for millions of years after all volcanic activity at the site has ceased.
VEI-8 volcanic events have included eruptions at the following locations (with estimates of the volume of erupted material at the event):
- 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 (2,800 km³)
- Valle Grande, New Mexico, United States
- Yellowstone Caldera, Wyoming, United States
- La Garita Caldera, Colorado, United States (over 5,000 km³)
The most recent VEI-8 eruption was at Lake Toba, Sumatra (the Toba event), and occurred around 74,000 years ago, plunging the Earth into a volcanic winter.
The largest known eruption on Earth occurred at the La Garita caldera in the San Juan Mountains approximately 28 million years ago.
Large igneous provinces
Large igneous provinces are remains of mega-colossal flood basalts that extruded enormous quantities of basaltic lava flat and deep over large areas, even covering entire sections of continents. 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 flood basalts significantly large enough to form these large igneous provinces 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. Large igneous provinces include eruption events at:
- Brazilian Highlands, Brazil
- Columbia River Plateau, United States
- Deccan Traps, India
- Siberian Traps, Russian Federation
The two largest flood basalt events in historic time have been at Eldgjá and Lakagigar, both in Iceland. Both of these altered the landscape around them, but neither of these had an impact great enough to be considered supervolcanic events.
