Super volcanoes may give plenty of warning CLERMONT-FERRAND, France, Feb. 1 (UPI) -- Giant volcano eruptions that change global climate and even threaten to wipe out species may be predictable decades in advance, European researchers say. Tim Druitt of France's Blaise Pascal University said analysis of rock crystals from the Greek island of Santorini, site of an ancient super volcano eruption, suggests such events are preceded by a fast build-up of magma underground that could be detected using modern instrumentation. The largest volcanoes undergo "caldera-forming eruptions" with the amount of magma ejected so great it leaves a massive depression on the Earth's surface and a crater-like structure known as a caldera. Super volcanoes can lie dormant for hundreds of thousands of years before erupting, an researchers assumed seismic readings would give several months' notice warning. But the Santorini study suggests these events might be predictable much earlier, Druitt said. "When volcanoes awaken and when the magma starts to ascend to the surface, cracking rock as it does, it sends out signals," he told the BBC. What we're finding is that there's an acceleration phase of magma build-up on a time scale of a few decades, and that's surprisingly short given the thousands of years of repose that have preceded that eruption. Years, rather than months, of warning could prove vital, Druitt said. "What we're saying is that all caldera volcanoes, even those in remote regions of the globe, should be monitored using highly sensitive modern instruments in order to pick up these deep signals which may suggest reactivation," he said.