The crew of a JMSA aircraft recently observed that bubbling water near Minami Iwo-Jima had changed to an ashen brown color. Orange and yellow flotsam was seen in the area. [The location given for this observation was 23.48°N, 141.67°E, or 90 km SSE of Fukutoku-okanoba, in the vicinity of Minami-Hiyoshi seamount.] Activity was reported nearby (23.50°N, 141.92°E) in August 1975.

Geological Summary. Periodic water discoloration and water-spouting have been reported over the Minami-Hiyoshi submarine volcano since 1975, when detonation sounds and an explosion were also reported. It lies near the SE end of a coalescing chain of youthful seamounts, and is the only vent with recorded activity. The reported depth of the summit of the trachyandesitic volcano has varied between 274 and 30 m. The morphologically youthful seamounts Kita-Hiyoshi and Naka-Hiyoshi lie to the NW, and Ko-Hiyoshi to the SE.

Information Contacts: AFP; U.S. Defense Mapping Agency.