Sanbesan stratovolcano, near the northern coast of SW Honshu, has a summit cut by a small caldera about 1 km in diameter. The highest point on the dacitic-to-andesitic volcano is O-Sanbe, at the northern end of the complex. There have been several large explosive eruptions during the Pleistocene and one strong Holocene eruption from the Taiheizan lava dome about 3,700 years ago. This eruption was accompanied by pyroclastic flows that swept down the NE-to-SE flanks and traveled 9 km down the Hayamizu River to the SW. Younger, undated eruptions have also occurred (Machida and Arai, 1992).