Zaozan [Zaosan] Volcano — Japan

The Zaozan (or Zaosan) volcano group consists of a complex cluster of stratovolcanoes in north-central Honshu about 40 km W of Sendai Bay. The Pleistocene Ryuzan volcano forms the western group (Nishi-Zao), and Byobu and Fubo volcanoes form the southern group (Minami-Zao). The complex was constructed over granitic basement rocks thus has a relatively small volume. The 7 km3 Zaozan volcano proper forms the central group (Chuo-Zao), a complex topped by several lava domes and the Goshikidake tuff cone, aligned NW-SE. Several episodes of edifice collapse produced debris avalanches during the Pleistocene. Goshikidake contains the active Okama crater, filled with a colorful, strongly acidic crater lake; it has been the source of most of the frequent eruptions recorded since the 8th century CE.