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Friday, January 11, 2013

Yellowstone and Supervolcanoes Definition, Mechanics, History, Threat Nature and Potential Future Risk A Research Study


Hidden Beneath the Earth’s surface lie one of the most destructive and yet least understood natural phenomena in the world—supervolcanoes. The term “supervolcano” implies an eruption of magnitude 8 on the Volcano Explosivity Index. A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruptions on Earth, Only a handful exist in the world but when one erupts it will be unlike any volcano humanity has ever witnessed. A super-eruption would equal the force of 1,000 Hiroshima atomic bombs exploding every second. A supervolcano is the most destructive force on this planet. “A super-eruption is the world’s biggest bang.” says Aon Benfield  University College London Hazard Research Centre Director and Geohazards Professor Bill McGuire. “It’s a volcanic explosion big enough to dwarf all others and with a reach great enough to affect everyone on the planet.” [11]
An event as massive as a super-eruption would change the Earth and human society forever. 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. The actual explosivity of these eruptions varies, but the sheer volume of extruded magma and gas is immense enough to radically alter the landscape and severely damage global climate for years, with a cataclysmic effect on life.
It’s difficult to predict the full devastation that would follow. The greatest danger would be within 1,000 km of the blast where 90 percent of people could be killed. 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. “The whole of a continent might be covered by ash, which might take many years—possibly decades—to erode away and for vegetation to recover.” Said University of Rhode Island Graduate school of oceanography NATO postdoctoral fellow and University of Bristol Department of Earth Sciences Chaning Wills Chair of Geology Robert Stephen John Sparks. [11] And it would devastate the planet. Experts say such an event would have a colossal impact on a global scale. Such a giant eruption would have regional effects such as falling ash and short-term (years to decades) changes to global climate. We know there would be great loss of life and ill health, changes to our planet and major economic losses. The fallout from a super-eruption would cause a volcanic winter, devastating global agriculture and causing mass starvation. The volcanic winter resulting from a super-eruption could last several years of decades, and according to recent computer models and predictions could cause cooling of global annual average temperatures on a global scale from 5 to 10 degrees C, depending on the scale of the eruption. Experts say colder temperatures could last 6-10 years, before gradually returning to normal.
Such an eruption would have a similar effect as a 1.5 km-diameter space rock striking Earth. But the chances of a supervolcano are twelve times more likely than a large globally destructive asteroid or meteorite impact. While it may in the future be possible to deflect asteroids or somehow avoid their impact, even science fiction cannot produce a credible mechanism for averting a super-eruption.
Volcanic Explosivity Index-8 eruptions (VEI-8 for short) are mega-colossal events that extrude at least more than 1,000 cubic kilometers (240 cubic miles) of magma (partially molten rock) and pyroclastic material. Granted, it’s not the typical volcano, either in scale (it’s huge), appearance (it’s a vast depression, not a single mountain) or frequency of eruption (at least hundreds of thousands of years apart). A super-eruption is a scaled up version of a typical volcanic outburst, explains Sparks. [11]
Supervolcanoes differ from normal volcanoes in many ways. The main feature is a large magma chamber, which is an underground reservoir filled with flowing hot rock under enormous pressures. A supervolcano also differs from a regular volcano in that there is often no mountain peak associated with it. The stereotypical volcano is a towering cone, but supervolcanoes form in depressions in the ground called calderas.
About forty supervolcanoes are dotted around the globe. Although they’re called “super”, most people would have trouble spotting a supervolcano. Some are identifiable only by the deep layers of ash they leave behind, such as the more than 1,000 cubic miles of tuff dumped in Eastern Africa and the Red Sea by a mystery eruption somewhere in Ethiopia. Other supervolcanoes would likely include the large caldera volcanoes of Japan, Indonesia, and South America.
There are other supervolcanoes on Earth, some of which erupted in prehistoric times, and could erupt again. Several super-eruptions large enough to cause global disaster may occur every 100,000 years. Volcanoes that produced exceedingly voluminous pyroclastic eruptions and formed large calderas in the past 2 million years include Yellowstone, Long Valley in Eastern California, Toba in Indonesia, and Taupo in New Zealand.
The most recent such supervolcano eruption event on Earth occurred 74,000 years ago at the Lake Toba Caldera in what is now Sumatra, Indonesia. A volcano called Toba blew with a force estimated at 10,000 times bigger than Mount Saint Helens. It created a global catastrophe dramatically affecting life on Earth, plunging the planet into a volcanic winter. Climatologists now know that Toba blasted so much ash and sulfur dioxide into the stratosphere that it blocked out the sun, causing the Earth’s temperature to plummet. Temperatures plummeted by up to 21 degrees at higher latitudes, according to research by New York Academy of Sciences Geological Sciences Section Chair and New York University Earth and Environmental Science Program Associate Professor of Biology Michael Robert Rampino. Ash darkened the sky all around the planet, blocking the sun’s rays and cooling the Earth’s atmosphere, which took years to recover. Rampino has estimated three-quarters of the plant species in the Northern hemisphere perished. [10]
It’s also true that three of the most astonishing volcanic eruptions in the geologic record, each hundreds to thousands of time the volume of 1980’s Saint Helens eruption, occurred around what is now Yellowstone National Park, which includes parts of Wyoming, Montana, and Idaho. Identified by an explorer in 1871, the massive Yellowstone “caldera”, a depression in the Earth equivalent to a crater top, is some 1,500 square miles.
Yellowstone National Park sits atop a subterranean chamber of molten rock and gases so vast that the region, known for its geysers, is arguably one of the largest active volcanoes in the world. “Yellowstone is much larger than any other volcanic feature in North America.” Says University of Utah Emeritus Professor of Geology and Geophysics Robert Smith. “People don’t realize this.” [3][12]
“To the public, an active volcano is one that’s erupting now.” Says U.S. Geological Survey research geologist Jacob B. Lowenstern. [4] Although Yellowstone is not erupting, it is active, and the evidence is everywhere.
The Yellowstone region has produced three exceedingly large volcanic eruptions in the past 2.1 million years. The first of Yellowstone’s three big eruptions was 2.1 million years ago, the next was 1.3 million years ago, and the last was 640,000 years ago. The first of these caldera-forming eruptions 2.1 million years ago created a widespread volcanic deposit known as Huckleberry Ridge Tuff. This titanic event, one of the five largest individual volcanic eruptions known anywhere on Earth, formed a caldera more than sixty miles (100 km) across. A similar smaller eruption occurred 1.3 million years ago. But the region’s most recent such major caldera-forming eruption at Yellowstone occurred some 640,000 years ago. It created the 35-mile-wide fifty-mile-long (55 by 80 km) Yellowstone Caldera, ejected 8,000 times the amount of ash and lava of Mount Saint Helens, and spread a layer of volcanic ash over most of the North American continent.
There are several levels of eruptions smaller than Huckleberry Ridge and still much larger and more destructive than any volcano ever witnessed by modern man. Smaller explosive eruptions, similar to the 1980 Mount Saint Helens eruption, occur approximately every 20,000 years. “Two of the three eruptions put out enough volcanic ash to spread a cloud all the way to the Mississippi River and the Gulf of Mexico.” Says Howard Heasler of the U.S. Geological Survey. [4] Huge volumes of volcanic ash were blasted high into the atmosphere, and deposits of this ash can still be found in places as distant from Yellowstone as Iowa, Louisiana, and California.
Other new information is being uncovered all the time. Scientists have very few answers, but they do know that the impact of a Yellowstone eruption is terrifying to contemplate. There is no argument that a major eruption at Yellowstone in modern times would be devastating. If another caldera-forming eruption were to occur at Yellowstone, it’s effects would be worldwide. A modern full-force Yellowstone eruption would kill millions, directly and indirectly, and would make every volcano in recorded human history look minor by comparison. A full-scale eruption of the Yellowstone supervolcano could result in millions of deaths locally and catastrophic climatic effects globally. Huge areas of the USA would be destroyed. The US economy would probably collapse, and thousands might die. The surrounding states of Montana, Idaho, and Wyoming would be affected, as well as other places in the United States and the world. Thick ash deposits would bury vast areas of the United States, and injection of huge volumes of volcanic gasses into the atmosphere could drastically affect global climate.
Fortunately, there is little indication that such an eruption is imminent in the near future, although study of Yellowstone is ongoing and the system is not yet completely understood. Geologists are uncertain whether Yellowstone is winding down from the third eruption or ramping up to a fourth. However, catastrophic eruptions occur so infrequently in the geologic record that it is statistically not likely anytime soon. The odds of a globally destructive volcano explosion in any given century are extremely low, and scientists cannot predict when the next one will occur. Given Yellowstone’s past history, the yearly probability of another caldera-forming eruption could be calculated as 1 in 730,000 or 0.00014%. This probability is roughly similar to that of a large (1 kilometer) asteroid hitting the Earth. Such eruptions are quite frequent on a geological timescale, although not one has occurred on Earth in the short time that an interdependent human civilization has existed. In fact, super-eruptions from supervolcanoes have occurred on a geological timescale so vast that a study by the Geological Society of London declared an eruption on the scale of Yellowstone’s biggest (the Huckleberry Ridge eruption 2.1 million years ago) occurs somewhere on the planet only about once every million years. [11] However, the number is based simply on averaging the two intervals between the three major past eruptions at Yellowstone; this is hardly enough to make a critical judgment. While those eruptions have been spaced roughly 800,000 and 660,000 years apart, three events are not enough statistically to declare this an eruption pattern, explains Smith. [3] Heasler demurs. “Three data points do not make a compelling argument for almost anything in science.” He says. [4]
Fortunately, the Yellowstone volcanic system shows no signs that it is headed toward such an eruption. Technically, the next eruption could happen anytime. Ye the geologists that monitor it are unconcerned about a large imminent eruption. Though Yellowstone could erupt again someday, there is no evidence that the caldera is readying for another massive blast, says Smith. [3] [12] Lowenstern shares that outlook. [4]
Volcanologists with the U.S. Geological Survey believe that supervolcanoes are likely to give decades, even centuries, of warning signs before they erupt. The scientists think those signs would include lots of earthquakes. Massive bulging of the land, an increase in small eruptions, “swarms of earthquakes in specific areas, changes in the chemical composition of lavas from smaller eruptions, changes in gasses escaping the ground and, possibly, large-scale cracking of the land. None of these indicators are present at Yellowstone, says Smith. [4]
Bibliography
  1. Bindeman, I.N. “The Secrets Of Supervolcanoes.” Scientific American. June 2006. 36-43. http://www.scientificamerican.com/article.cfm?id=the-secrets-of-supervolca
  2. Blank, H.R., Christiansen, R.L., Eaton, G.P., Gettings, M.E., Iyer, H.M., Mabey, D.R. Pitt, A.M., & Zietz, I. “Magma Beneath Yellowstone National Park.” Science. 1975. 787-796. http://www.sciencemag.org/content/188/4190/787.long
  3. Christiansen, R.L. & Smith, R.B. “Yellowstone Park As A Window On The Earth’s Interior.” Scientific American. 1980. 104-17.
  4. Christiansen, R.L., Heasler, H. Lowenstern, J.B., Morgan, L.A. & Smith, R.B. “Steam Explosions, Earthquakes, And Volcanic Eruptions—What’s In Yellowstone’s Future?” U.S. Geological Survey Fact Sheet. 2005. 2005-3024. http://pubs.usgs.gov/fs/2005/3024/http://walrus.wr.usgs.gov/infobank/programs/html/factsheets/pdfs/2005_3024.pdf
  5. Dzurisin, D. Svarc, J., Thatcher, W. & Wicks, C. “Uplift, Thermal Unrest, and Magma Intrusion At Yellowstone Caldera.” Nature. 2006. 72-75. http://www.nature.com/nature/journal/v440/n7080/full/nature04507.html
  6. Keefer, W.R. “The Geologic Story Of Yellowstone National Park.” U.S. Geological Survey Bulletin. 1971. 1347. http://pubs.usgs.gov/bul/1347/report.pdf
  7. Kuntz, M.A. & Link, P.K.; Eds. Morgan, L.A., Pierce, K.L. & Platt, L.B. “The Track Of The Yellowstone Hot Spot: Volcanism, Faulting And Uplift. Regional Geology Of Eastern Idaho And Western Wyoming.” Geological Society of America Bulletin. 1-53. http://www.rcn.montana.edu/pubs/pdf/1992/YellowstoneHotSpot11.pdf
  8. O’Hanlon, L. “Yellowstone’s Super Sisters.” Discovery. February 20, 2007. http://dsc.discovery.com/convergence/supervolcano/others/others.html
  9. O’Hanlon, L. “What’s Under Yellowstone? America’s Explosive Park.” Discovery. February 20, 2007. http://dsc.discovery.com/convergence/supervolcano/under/under.html
  10. Rincon, Paul. “Experts Weigh Supervolcano Risks.” BBC News. 2005. http://news.bbc.co.uk/2/hi/science/nature/4326987.stm
  11. Self, S. & Sparks, S. et al. “Super-Eruptions: Global Effects And Future Threats.” Report Of A Geological Society Of London Working Group. 2005. http://www.geolsoc.org.uk/en/Education%20and%20Careers/Resources/Papers%20and%20Reports/~/media/shared/pdfs/education%20and%20careers/Super_eruptions.ashx
  12. Smith, R.B. “Windows Into Yellowstone: An Interview With Geologist And Geophysicist Robert B. Smith.” Yellowstone Science. 2000. 1-13. http://www.greateryellowstonescience.org/files/pdf/YS_Smith.pdf

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