Mount Aso has one of the world’s largest calderas, measuring about 25 kilometres across.
Aso is a volcanic complex in Kyushu, Japan. Its enormous caldera formed through several giant explosive eruptions, especially events between roughly 300,000 and 90,000 years ago. The caldera is about 25 kilometres north to south and 18 kilometres east to west, and it contains towns, farmland, and transport routes.
The modern central cone group includes Nakadake, the most active part of the complex. Visitors often refer to Aso as one volcano, but it is better understood as a large volcanic system with multiple cones and vents.
Aso’s size does not mean its entire caldera is a single crater. A caldera is a much larger depression formed when a magma chamber empties and the overlying ground collapses.