Report on Minami-Hiyoshi (Japan) — February 1977
Natural Science Event Bulletin, vol. 2, no. 2 (February 1977)
Managing Editor: David Squires.
Minami-Hiyoshi (Japan) Two zones of discolored water observed from the air
Please cite this report as:
Global Volcanism Program, 1977. Report on Minami-Hiyoshi (Japan) (Squires, D., ed.). Natural Science Event Bulletin, 2:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197702-284131
Minami-Hiyoshi
Japan
23.5°N, 141.935°E; summit elev. -107 m
All times are local (unless otherwise noted)
On 10 January, a JMSA aircraft noted two adjacent zones of discolored water. One zone was 5.5 x l km, colored gray and milky white at the center. Each color was thought to have been generated by a separate vent. The second zone, 6.5 km long, was pale green to yellowish-brown. No volcanic ejecta were observed. By 24 January, activity had decreased markedly. Depth at the site is reported to be 130 m.
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: JMA, Tokyo; Japanese Press.
