, is also known as Aso Volcano and in this sense is the largest active volcano in Japan, and is among the largest in the world. Common use relates often only to the somma volcano in the centre of the Aso Caldera. It stands in Aso Kujū National Park in Kumamoto Prefecture, on the island of Kyushu. Its tallest peak, Takadake, is above sea level. Mount Aso is in a fairly large caldera (25 kilometers (16 miles) north-south and 18 km (11 mi) east-west) with a circumference of around , although sources vary on the exact distance. Geography The central cone group of Aso consists of five peaks, often called the "Five Mountains of Aso" (阿蘇五岳): Mt. Neko, Mt. Taka (also called Takadake or Taka-Dake), Mt. Naka (also called Nakadake or Naka-Dake), Mt. Eboshi, and Mt. Kishima (also called Kishimadake or Kishima-Dake ). The highest point is the summit of Mt. Taka, at 1592 m above sea level. The crater of Mt. Naka, the west side of which is accessible by road, contains an active volcano which continuously emits smoke and has occasional eruptions. Only the northernmost crater (the first crater) has been active for the last 70 years—1974, 1979, 1984–1985, 1989–1991, 2009, 2011, 2015, 2016 and 2021. The present Aso Caldera formed as a result of four huge caldera eruptions occurring over a range of 90,000–300,000 years ago. The caldera, one of the largest in the world, contains the city of Aso as well as Takamori and Minamiaso enclosing the caldera extends about 18 km east to west and about 25 km north to south. Viewpoints from the somma overlooking the caldera are perched upon lava formed before the volcanic activity which created the present caldera. Ejecta from the huge caldera eruption 90,800 years ago covers more than 600 km3 and roughly equals the volume of Mount Fuji; with a pyroclastic flow plateau that covered a significant part of Kyushu. History The eruption which formed the present somma occurred approximately 300,000 years ago. Four large-scale eruptions (Aso 1 – 4) occurred during a period extending from 300,000 to 90,000 years ago. As large amounts of pyroclastic flow and volcanic ash were emitted from the volcanic chamber, a huge depression (caldera) was formed as the chamber collapsed. The fourth eruption (Aso 4) was the largest, with volcanic ash covering the entire Kyushu region and even extending to Yamaguchi Prefecture. Mt.