Most supereruptions occur in areas that remain active over millions of years but enjoy a long repose period, so don't place too much confidence in Yellowstone's apparent calm. Broadly speaking, the longer the dormancy, the bigger the boom [source: Geological Society of London].
Like other supervolcanic areas, Yellowstone sits on a long-active tectonic zone, a weakened and thinned crust overlying a 2,500 F (1,370 C) magma dome rising from the upper mantle. This dome has melted and broken into the crust to create two magma chambers roughly 5-7 miles (8-11 kilometers) underground, each measuring 30-plus miles (48-plus kilometers) across [source: Encyclopedia Britannica]. These magma chambers are filled with an amalgam of magma, semisolid rock and dissolved gases like water vapor and carbon dioxide.
Over centuries and millennia, additional magma builds up, delivering more heat and pressure, pushing overlaying ground upward little by little. If the chamber receives a steady and substantial supply of hot magma, pressure builds in an often cyclical process called incubation. If it doesn't, then some material solidifies and sinks, removing pressure. The sheer volume of a supervolcano's magma chamber means that incubation requires a heat delivery rate 2-3 orders of magnitude greater than that of a traditional volcano [sources: Achenbach; Klemetti].
Eventually, overpressure creates fractures along the dome's periphery, venting pressure from the chamber. The gas-filled magma blasts skyward, raining ash and debris over hundreds of miles and releasing deadly pyroclastic flows -- fast-moving, thick clouds of gas, ash and rocks boiling away from the eruption at 1,470 F (800 C) – across tens of thousands of square miles [sources: Achenbach; Geological Society of London].
Additional blasts pop off periodically for weeks. Ash drifts down on a regional scale, filling the sky with pollutants and blanketing tens of millions of square miles in inches of crop-killing ash [sources: Geological Society of London; Klemetti]. Until it settles, anyone within thousands of miles around risks breathing tiny glass needles, bursting pulmonary blood vessels and drowning in a slurry of ash and lung moisture [sources: Achenbach; Geological Society of London; Tyson]. Ash collapses roofs, pollutes vital water sources and gums up vehicle engines, sparking a crisis of food production, transportation, communication and economics lasting months to years [sources: Geological Society of London; Klemetti].
Within weeks, dust and sulfate aerosols encircle the globe, filtering out sunlight and cooling global average temperatures by an estimated 5-9 F (3-5 C) for several years afterward [sources: Geological Society of London; Klemetti; Marshall]. One-third of the U.S., particularly the states of Montana, Idaho and Wyoming, remain uninhabitable for months, possibly years [sources: Tyson; USGS].
Thankfully, the odds argue against this happening any time soon. But another supereruption, someday, somewhere in the world, is inevitable. Maybe it's time we got started on that Mars colony after all.
Author's Note: How Supervolcanoes Work
Supervolcanoes present a fascinating subject, but a difficult one to write about. On the one hand, we marvel at the tremendous scale revealed through their vast calderas and high-piled deposits, and we can intuit their climate-shifting capacity via ice cores, tree rings and microbes that alter their structure in response to climate changes. On the other, there's just so much we do not know about the contents of their magmas and the dynamics that drive their deep-welling plumes. Even seemingly harmless chemicals and materials might cause untold perturbations in the climate if dumped into the atmosphere in sufficient amounts. We just don't know.
And that's what's terrifying about these behemoths. Despite all our knowledge about volcanic and tectonic events, and even though supervolcanoes exist right here on Earth, in some ways they might just as well be extinction-level meteors from outer space. Our ability to predict them, or to do anything about them, is equally small, and in both cases we are left clinging to the cold comfort of long odds.
More Great Links
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- Associated Press. "Magnitude-4.8 Earthquake Shakes Yellowstone Park." The New York Times. March 30, 2014. (Feb. 6, 2015) http://www.nytimes.com/aponline/2014/03/30/us/ap-us-yellowstone-quakes.html
- Associated Press. "Yellowstone Fighting Online Supervolcano Rumors." The New York Times. April 4, 2014. (Feb. 6, 2015) http://www.nytimes.com/aponline/2014/04/04/us/ap-us-travel-brief-yellowstone-quake-bison.html?_r=0
- Aurthur, Kate. "Arts, Briefly; Strong Ratings for Spike." The New York Times. April 18, 2005. (Feb. 6, 2015) http://query.nytimes.com/gst/fullpage.html?res=9D0CE2DF1F3EF93BA25757C0A9639C8B63
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- Cartlidge, Edwin. "Supervolcano Drilling Plan Gets Go-Ahead." Science. May 18, 2012. (Feb. 12, 2015) http://news.sciencemag.org/2012/05/supervolcano-drilling-plan-gets-go-ahead
- Encyclopedia Britannica. "Yellowstone National Park." (Feb. 9, 2015) http://www.britannica.com/EBchecked/topic/652774/Yellowstone-National-Park
- Friedman-Rudovsky, Jean. "Growth Spurt at a Bolivian Volcano is Fertile Ground for Study." The New York Times. Feb. 13, 2012. (Feb. 6, 2015) http://www.nytimes.com/2012/02/14/science/a-fascinating-growth-spurt-at-the-uturuncu-volcano-in-bolivia.html
- Geological Society of London. "Super-eruptions: Global Effects and Future Threats." 2005. (Feb. 6, 2015) https://www.geolsoc.org.uk/Education-and-Careers/Resources/Papers-and-Reports/Super-eruptions
- Gregg, Patricia M., et al. "Development, Evolution and Triggering of Supereruptions." (Feb. 8, 2015) https://gsa.confex.com/gsa/2011AM/finalprogram/abstract_197370.htm
- Klemetti, Erik. "Dr. Shanaka de Silva Answers Your Questions About Supervolcanoes, Uturuncu and More." Wired. Feb. 14, 2012. (Feb. 11, 2015) http://www.wired.com/2012/02/dr-shanaka-de-silva-answers-your-questions-about-supervolcanoes-uturuncu-and-more/
- Malfait, Wim et al. "Supervolcano Eruptions Driven by Melt Buoyancy in Large Silicic Magma Chambers." Nature Geoscience. Vol. 7. Page 122. Jan. 5, 2014. (Feb. 9, 2015) http://www.nature.com/ngeo/journal/v7/n2/full/ngeo2042.html
- Marshall, Michael. "Supervolcano Eruptions May Not be So Deadly After All." New Scientist. April 29, 2013. (Feb. 8, 2105) http://www.newscientist.com/article/dn23458-supervolcano-eruptions-may-not-be-so-deadly-after-all.html#.VNfScvnF98E
- Oxford Dictionary of Science. Alan Isaacs, John Daintith and Elizabeth Martin, eds. Oxford University Press, 2003.
- Robinson, Dean. "Let's Hope the Boom Times Don't Come to Yellowstone." The New York Times. July 17, 2013. (Feb. 6, 2015) http://6thfloor.blogs.nytimes.com/2013/07/17/lets-hope-the-boom-times-dont-come-to-yellowstone/
- Rowlett, Russ. "Volcanic Explosivity Index." From University of North Dakota's Volcano World. (Feb. 5, 2015) https://www.unc.edu/~rowlett/units/scales/VEI.html
- Self, Stephen, et al. "The Atmospheric Impact of the 1991 Mount Pinatubo Eruption." In FIRE and MUD: Eruptions and Lahars of Mount Pinatubo, Philippines, Christopher G. Newhall and Raymundo S. Punongbayan, eds. U.S. Geological Survey. 1996. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990021520.pdf
- Tharoor, Ishaan. "Krakatoa." Time. Aug. 31, 2010. (Feb. 16, 2015) http://content.time.com/time/specials/packages/article/0,28804,2014572_2014574_2014635,00.html
- Tyson, Peter. "Lessons From a Supervolcano." NOVA. Sep. 26, 2006. (Feb. 12, 2015) http://www.pbs.org/wgbh/nova/earth/lessons-supervolcano.html
- Tyson, Peter. "Surviving a Supereruption." PBS. Sep. 26, 2006. (Feb. 6, 2015) http://www.pbs.org/wgbh/nova/earth/surviving-a-supereruption.html
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