For centuries humans have puzzled over volcanoes. Why do volcanoes erupt? How do they work? Professor Sigurdsson, an eminent volcanologist whose work has been featured in two National Geographic television specials, traces in this book the history of ideas about volcanoes, a history spanning more than 2,000 years --- from the notions of the ancient Greeks to the more scientific, experimentally based theories of today. Underlying his stories is an endeavour to answer the question: How do rocks melt in the Earth?