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Supervolcanoes? Pfft.

I've never worried much about a gigantic asteroid hitting the earth, probably because I've always been more interested in another low-probability, Earth-shattering cataclysm: namely, the active supervolcano sitting beneath Yellowstone National Park. Supervolcanoes, mind you, aren't just "big" volcanoes like Krakatoa or Vesuvius; they're utterly monstrous—the last time one erupted was 74,000 years ago, when Toba in Sumatra slathered the atmosphere in ash and may have wiped out all but 10,000 or so human beings on the planet. Needless to say, having the behemoth under Yellowstone erupt—with it's 1,500-square-mile caldera (right)—would make us all forget about all that stock-market turmoil pretty quickly. Oh yeah, and having exploded 642,000 years ago, some scientists have calculated Yellowstone's due for another burp… sometime around now.

Anyway, here's the good news (a month or two old, but worth passing along even so): Recently, Derek Schutt of Colorado State University and Ken Dueker of the University of Washington estimated that the possible source of eruptions, a plume of hot mantle 50 miles below the surface in Yellowstone… isn't actually that hot, "only" about 1,450 C, cooler than the mantle plume you'd find, say, under Hawaii. This might be a sign that the plume's been disconnected from its heat source deeper down in the Earth's core—which could mean that it's dying out, making titanic eruptions less likely. Not everyone's so cheery—one geophysicist told New Scientist that "Ruling out a future catastrophic eruption would be foolish," and other recent studies have found disturbing activity on the march in the Yellowstone caldera. Still, maybe it's time to start freaking out about asteroids instead…

--Bradford Plumer