Yellowstone: the next ‘big one’ is anyone’s guess — but you don’t want to be here scientist warn

June 9, 2011 – UTAH – It’s no mere doomsday pseudoscience: The Yellowstone supervolcano really could be the end of us all. When the Yellowstone Caldera — the name of the national park’s geographic structure, which roughly translates as “caldron” — blows its lid, much of the continental United States will get covered in a blanket of ash. That ash will clog the atmosphere enough to block out the sun, disrupting the global climate enough to cause mass extinctions. The last full-scale eruption of that kind occurred 640,000 years ago, and the ones prior to that occurred 1.3 million years and 2.1 million years ago. Interspersed with the big ones have been smaller-scale but still major eruptions, most recently 70,000 years ago. At the Yellowstone Volcano Observatory (YVO), an outpost run by the U.S. Geological Survey in conjunction with Yellowstone National Park and the University of Utah, a team of volcanologists continuously monitors the sleeping giant’s tectonic activity. They listen to its rumblings (which are streamed online in real time) for clues as to what’s brewing below the surface. Jacob Lowenstern, scientist-in-charge at YVO, told us what they’re listening for and what they know so far about the next “big one.” “Earthquake swarms” (that is, series of quakes), ground deformation, and hydrothermal (steam) explosions can all signal impending volcanic activity, Lowenstern said. All three are common at Yellowstone — the area has a history of earthquake swarms and uplift/subsidence cycles and is practically always astir — but for now, they aren’t intense enough to warrant concern about an impending volcanic eruption. “It is clear from geological studies that the kind of activity we see at Yellowstone has been occurring for a very long time, and that such activity does not imply that an eruption is coming anytime soon,” Lowenstern wrote in an email. “Given that one hasn’t happened at Yellowstone for 70,000 years, and given that we know there are lots of earthquake swarms and episodes of ground deformation, it is clear that it takes quite a bit to cause Yellowstone to erupt.” During the five years since the YVO team began posting monthly volcano alert levels, the level has stayed at “normal.” That will change, Lowenstern explained, only if an intense swarm of more than 500 earthquakes, some with magnitudes greater than 4.5, is accompanied by either a rapid change in ground displacement — for example, a rise or fall in the Earth’s crust of more than 2 inches in 30 days — or a large hydrothermal explosion. –MSNBC