Mount Aso

Mount Aso is a somma volcano in Kumamoto Prefecture on the Japanese island of Kyushu, its tallest peak, Takadake, reaching 1,592 meters, and it ranks as the second largest active volcano in Japan after Mount Fuji. Its caldera measures about 25 kilometers north to south and 18 kilometers east to west, with a circumference of roughly 120 kilometers, formed by four huge caldera-forming eruptions occurring between about 300,000 and 90,000 years ago; the somma, the remnant of the original volcanic cone, erupted around 300,000 years ago, with younger cones building up inside the caldera afterward. Mount Aso has remained active into the present, with documented eruptions in 1974, 1979, 1984-1985, 1989-1991, 2009, 2011, 2015, 2016 and an ongoing episode beginning October 20, 2021; the northernmost of its craters has been the only consistently active site over the past 70 years. This entity documents Mount Aso specifically as a geological formation, a somma volcano built inside one of Japan's largest calderas.