ROME (Reuters) - An underwater volcano with a base larger than Washington D.C. has been discovered just off the shores of Sicily, a scientist with Italy's National Institute of Geophysics and Vulcanology said on Thursday. The volcanic structure, which incorporates peaks previously thought to be separate volcanoes, was named Empedocles after the Greek philosopher who named the four classic elements of earth, air, fire and water. Legend has it that the philosopher died by throwing himself into Mount Etna, the nearby Sicilian volcano. Giovanni Lanzafame, who works at the institute and led the research, said Empedocles was at least 400...