Supervolcano

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 Quaternary 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.

Contents 1 Terminology 2 Large igneous provinces 3 Massive explosive eruptions 3.1 Known super eruptions 3.1.1 VEI 8 3.1.2 VEI 7 4 Media portrayal 5 See also 6 Notes 7 References 8 External links

[edit] 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 term 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.

[edit] Large igneous provinces

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 kilometers. 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, coincident with the extinction of the dinosaurs at the end of the Cretaceous. Because the largest flood basalt event (the Siberian Traps) occurred around 250 Ma and was coincident with the largest mass extinction in history (end Permian), and the second largest flood basalt event (The Deccan Traps) occurred around 65 Ma and was coincident with the second largest extinction event (end Cretaceous), research continues into the effect of these volcanic outpourings and whether they contributed to mass extinctions.

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.

[edit] 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)^[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.

[edit] Known super eruptions

Estimates of the volume of ejected material are given in parentheses.

[edit] VEI 8

VEI 8 eruptions have happened in the following locations.

• Lake Taupo, Taupo Volcanic Zone, North Island, New Zealand—Oruanui eruption ~26,500 years ago (~1,170 km³)
• Lake Toba, Sumatra, Indonesia—~74,000 years ago (~2,800 km³)
• Whakamaru, Taupo Volcanic Zone, North Island, New Zealand—Whakamaru Ignimbrite/Mount Curl Tephra ~254,000 years ago (1,200-2,000 km³)^[7]
• Yellowstone Caldera, Lava Creek Tuff, Wyoming, United States, Yellowstone hotspot—640,000 years ago (1,000 km³)^[8]
• Island Park Caldera, Huckleberry Ridge Tuff, Idaho/Wyoming, United States, Yellowstone hotspot—2.1 million years ago (2,500 km³)^[8]
• Cerro Galan, Catamarca Province, Argentina—2.5 million years ago (1,050 km³)
• Atana Ignimbrite, Pacana Caldera, northern Chile—4 million years ago (2,500 km³)^[9]
• Heise volcanic field, Kilgore Tuff, Idaho, United States, Yellowstone hotspot—4.5 million years ago (1,800 km³).^[10]
• Heise volcanic field, Blacktail Tuff, Idaho, United States, Yellowstone hotspot—6.6 million years ago (1,500 km³).^[10]
• La Garita Caldera, Colorado, United States—Source of the enormous eruption of the Fish Canyon Tuff ~27.8 million years ago (~5,000 km³)

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.^{[citation needed]}

[edit] VEI 7

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]

• Tambora, Sumbawa Island, West Nusa Tenggara, Indonesia—1815 (160 km³), the following year 1816 became known as the "Year Without a Summer"
• Baekdu Mountain, China/North Korea—~969 CE (96±19 km³)
• Lake Taupo, Taupo Volcanic Zone, North Island, New Zealand—Hatepe eruption ~181 CE (120 km³)^[17]
• Kikai Caldera, Ryukyu Islands, Japan—~6,300 years ago (~4,300 BCE) (150 km³)
• Macauley Island, Kermadec Islands, New Zealand—~6,300 years ago (~4,300 BCE) (100 km³)^[19][20]
• Aira Caldera, Kyūshū, Japan—~22,000 years ago (~110 km³)
• Rotoiti Ignimbrite, Taupo Volcanic Zone, North Island, New Zealand—~50,000 years ago (~240 km³)^[21]
• Campi Flegrei, Naples, Italy—39,280 ± 110 years ago (500 km³)
• Aso, Kyūshū, Japan—four large explosive eruptions between 300,000 to 80,000 years ago (last one >600 km³)
• Reporoa Caldera, Taupo Volcanic Zone, North Island, New Zealand—230,000 years ago (~100 km³)* I. A. Nairn; C. P. Wood and R. A. Bailey (December 1994). "The Reporoa Caldera, Taupo Volcanic Zone: source of the Kaingaroa Ignimbrites". Bulletin of Volcanology 56 (6): 529–537. doi:10.1007/BF00302833. http://www.springerlink.com/content/mu1970l8163tp006. Retrieved 2010-09-16. 
• Mamaku Ignimbrite, Rotorua Caldera,Taupo Volcanic Zone, North Island, New Zealand—240,000 years ago (>280 km³)^[22]
• Matahina Ignimbrite, Haroharo Caldera, Taupo Volcanic Zone, North Island, New Zealand—280,000 years ago (~120 km³)^[23]
• Long Valley Caldera, Bishop Tuff, California, United States—~760,000 years ago (600 km³)
• Valles Caldera, New Mexico, United States—~1.15 million years ago (~600 km³)^[24]
• Mangakino, Taupo Volcanic Zone, North Island, New Zealand—three eruptions from 0.97 to 1.23 million years ago (each > 300 km³)^[25]
• Henry's Fork Caldera, Mesa Falls Tuff, Idaho, United States, Yellowstone hotspot—1.3 million years ago (280 km³)^[8]
• Pastos Grandes Ignimbrite, Pastos Grandes Caldera, 2.9 million years ago (>820 km³)^[26]
• Heise volcanic field, Walcott Tuff, Idaho, United States, Yellowstone hotspot—6.4 million years ago (750 km³).^[10]
• Bruneau-Jarbidge, Idaho, United States, Yellowstone hotspot—~10–12 million years ago (>250 km³) (responsible for the Ashfall Fossil Beds ~1,600 km to the east^[27])
• Bennett Lake Volcanic Complex, British Columbia/Yukon, Canada—~50 million years ago (850 km³)^{[citation needed]}

[edit] Media portrayal

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• 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][14][15]} 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 2006, the Sci Fi Channel aired the documentary Countdown to Doomsday which featured a segment called "Supervolcano". The same year, ABC News aired the documentary Last Days on Earth, which featured a segment called "Supervolcano". Also in 2006, the TV series Stargate Atlantis aired an episode called "Inferno" whose plot revolves around the discovery and subsequent eruption of a supervolcano on another planet.

• 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 2009, the Toba supervolcano was featured in the episode "Fire and Ice" of Animal Planet series Animal Armageddon.

• Also in 2009, the Yellowstone supervolcano erupts during the apocalyptic movie 2012.

[edit] See also

• Risks to civilization, humans and planet Earth
• Toba catastrophe theory
• Timetable of major worldwide volcanic eruptions

[edit] Notes

[edit] References

• Mason, Ben G.; Pyle, David M.; Oppenheimer, Clive (2004). "The size and frequency of the largest explosive eruptions on Earth". Bulletin of Volcanology 66 (8): 735–748. doi:10.1007/s00445-004-0355-9. 
• Timmreck, C.; Graf, H.-F. (2006). "The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study". Atmospheric Chemistry and Physics 6: 35–49. doi:10.5194/acp-6-35-2006. http://www.atmos-chem-phys.net/6/35/2006/acp-6-35-2006.html. 

[edit] External links

• Overview and Transcript of the original BBC program
• Yellowstone Supervolcano and Map of Supervolcanoes Around The World
• USGS Fact Sheet - Steam Explosions, Earthquakes, and Volcanic Eruptions - What's in Yellowstone's Future?
• Discovery Channel's site on "Supervolcano"
• Scientific American's The Secrets of Supervolcanoes
• Supervolcano at the Internet Movie Database
• Armageddon Online - Latest news covering super volcano activity since 1999