01 / Buried Trees in the Aso-4 Pyroclastic Flow
The fallen trees' direction showed thepyroclastic flow was guided west.
Three trees buried by the Aso-4 pyroclastic flow about 90,000 years ago, and its deposits, were found in 2017 at a revetment on a tributary of the Ōhi River. One of them is about 6.9 m long. The designation notes say the direction in which the trees fell confirms that the flow was strongly guided west along east-west mountain ranges and river valleys.
- Aso-4 pyroclastic flow, about 90,000 years ago
- 3 buried trees (one about 6.9 m long)
- National Natural Monument (gazetted 15 March 2022)

