Supervolcano season

There's still time to catch the BBC program dramatizing supereruptions of supervolcanoes, which airs today. Large calderas like the one that encompasses most of Yellowstone National Park can erupt again as they did in the Pleistocene, strewing ash and gas over much of the North American continent (or whatever continent they sit on). BBC science reporter Paul Rincon writes that geologists think there should be some planning begun for such things, which rival nuclear winter and cosmic impacts in their disastrous scope.