Signs of unrest have been reported from the volcano. According to a news article, d under the volcano recently, believed to be signs of increased internal fluid movements.
No volcanic earthquakes or significant deformation of the volcanic edifice have been recorded, that could suggest new magma rising, and currently, no eruption is expected to be likely in the near future. However, the volcano will now be observed with increased vigilance.
The Zaozan volcano group, the most active of northern Honshu, consists of a complex cluster of stratovolcanoes straddling the Pacific Ocean-Japan Sea divide. 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 as high as 1500 m and thus has a relatively small volume. The 7 cu km Zaozan volcano proper forms the central group (Chuo-Zao), a volcanic complex topped by several lava domes and the Goshikidake tuff cone, aligned along a NW-SE trend. 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 (pH 1.3). It has been the source of most of the frequent historical eruptions, which date back to the 8th century CE.
December 01, 2015. Zao, Honshu, Japan :
Source : nhk.or.jp , GVP
Photo : b. Bernard