In Italy lies a hidden "super volcano" that could kill millions. It lies across the bay of Naples from Pompeii. The boiling mud and sulphurous steam holes of the area west of Naples known as the Campi Flegrei or Phlegraean Fields, from the Greek word for burning, are a major tourist attraction. But the zone of intense seismic activity, which the ancients thought was the entrance to hell, also could pose a danger of global proportions with millions of people literally living on top of a potential future volcanic eruption. "These areas can give rise to the only eruptions that can have global catastrophic effects comparable to major meteorite impacts," said Giuseppe De Natale, head of a project to drill deep under the earth to monitor the molten "caldera". One such meteorite impact is thought to have caused the extinction of the dinosaurs 65 million years ago when debris thrown into the atmosphere from the huge explosion plunged the earth into darkness. Sci...