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Aso UNESCO Global Geopark is situated in the center of Kyushu, the southernmost of four main islands, in the Japanese archipelago, which is located in the circum-Pacific orogenic belt. The majority of Aso UNESCO Global Geopark lies within Aso Kuju National Park, which is overseen by the Ministry of the Environment. Aso Volcano is located in central Kyushu and is one of the most beautiful Quaternary caldera volcanoes in the world. Between 270,000 and 90,000 years ago, gigantic pyroclastic flow eruptions of andesitic to rhyolitic magma occurred four times in the volcanic field and formed the Aso caldera stretching 25 km north-south and 18 km east-west. Basement rocks consist of Quaternary Pre-Aso volcanic rocks, Cretaceous granites and sedimentary rocks, and Palaeozoic metamorphic rocks. Post-caldera central cones started to erupt soon after the last caldera-formed (90,000 years ago) and have produced large volumes of fallout tephra layers and lava flows. The rocks of the central cones are diverse; rhyolite, dacite, andesite, and basalt. Nakadake Volcano which is the only active central cone is one of the most active volcanoes in Japan. Its recent activity is characterized by ash and strombolian eruption and phreatic or phreatomagmatic explosion.