YAMAGUCHI—An eruption of Mount Aso in Kumamoto Prefecture 90,000 years ago created a pyroclastic flow that traveled 170 kilometers north to the Sabagawa river here, the longest such distance recorded ...

A man presses his hands together in prayer before a memorial cenotaph in the location that served as the media's "fixed point" when a pyroclastic flow hit the area, in Shimabara, Nagasaki Prefecture, ...