Volcanic activity on Stromboli, an island off the toe of Italy, sent a tidal wave crashing into the coastal village of Ginostra Dec. 30, overturning boats, damaging homes and scaring away tourists gathered for the New YearÂ’s holiday. Authorities are worried that a major eruption is imminent and have placed early warning sensors on buoys near Stromboli to warn of new tidal waves. Nearby islands, mainland Italy, and parts of Sicily are considered at risk.