Overview: Mt. Ontake is located on the border of Nagano and Gifu prefectures. Standing 3,067 meters above sea level, it is a popular daytrip hiking spot for mountain enthusiasts. Mt. Ontake was crowded with climbers around noon during a September vacation season, when the sudden stream-driven "phreatic eruption" occurred. Many climbers panicked as they encountered this unexpected natural phenomenon. Why couldn't this eruption be predicted? According to experts, there are 3 main types of volcanic eruptions, and the warning signs of phreatic eruptions are the hardest to detect. Now researchers are making advances to detect the slightest signs of an eruption using observation satellites and chemical approaches. Find out the latest on the research of volcanic predictions.