The gully in the foreground below Maekakeyama exposes deposits of the Oiwake pyroclastic flow, which was emplaced during a major explosive eruption in 1108 CE. This Plinian eruption, the largest from Asama during the Holocene, produced 0.4 km³ of asfall followed by emplacement of the 0.6 km³ Oiwake pyroclastic flow and the Butai lava flow down the NW flank from the crater. The summit of Maekakeyama collapsed after this eruption to form a 0.9 x 1.3 km crater.

Photo by Yukio Hayakawa, 1998 (Gunma University).

This image is made available under the Creative Commons BY-NC 4.0 license terms.

Asamayama