In the Kunimicho area, the deposits from the Older Unzen Volcano of 500,000 to 300,000 years ago were distributed and a large amount of magnetite (iron sand), produced by the weathered rocks, poured into the sea.
This iron sand was used for the Tatara Iron manufacture in the Middle Ages.
Around the seashore, you can also observe the deposits of pyroclastic flows caused by the catastrophic eruption of Aso Volcano 90,000 years ago.