Using the knowledge of past eruptions and their research on more recent blasts, scientists are becoming even better at predicting when and where a volcano will erupt. Every year, science unlocks more secrets of volcanoes. Almost every blast reveals new information about volcanic behavior. Scientists use this information to prepare the public for a volcanic eruptionand hopefully to save more lives in the process.

But no matter how much information scientists gather, volcanoes are still very unpredictable-and deadly. This fact was underscored in 1991 when the Japanese volcano Mount Unzen erupted, killing more than forty people, including a respected American scientist, Harry Glicken, and world-famous volcanologists Maurice and Katia Krafft. These professionals had long studied volcanoes and the deadly forces that accompany them; they completely understood the dangers of a volcanic eruption. They respected the power of volcanoes and observed all the safety measures dictated by their years of...