Report on Kaitoku Seamount (Japan) — February 1984
Scientific Event Alert Network Bulletin, vol. 9, no. 2 (February 1984)
Managing Editor: Lindsay McClelland.
Kaitoku Seamount (Japan) Large area of discolored water; small plumes
Please cite this report as:
Global Volcanism Program, 1984. Report on Kaitoku Seamount (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 9:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198402-284100
26.1217°N, 141.0955°E; summit elev. -95 m
All times are local (unless otherwise noted)
On 7 March at 1230, the crew of a Japan Maritime Self-Defense Force (JMSDF) transport plane flying about 130 km N of Iwo-Jima observed a fan-shaped zone of discolored sea water that extended about  km WSW from a submarine vent. The maximum width of the discolored zone was about 9 km. A helicopter flew over the area shortly thereafter and its crew estimated that the extent of the reddish-brown water was roughly as large as Iwo Jima Island (about 5 x 8 km).
The next morning, JMSA personnel observed continuous submarine eruptive activity. Gray or yellowish brown water was ejected every 10 minutes and waves spread outward from the vents. The sea colors included gray, white, yellowish brown, and reddish brown. JMSA observers saw neither plumes nor floating ejecta, although small white plumes and rocks or reefs were seen during a flight by the JMSDF at about noon the same day. On 12 March, personnel aboard a JMSDF patrol plane again saw floating material, and a plume about 100 m above sea level. Only discoloration was found during a JMSA flight 13 March. As of the 13th, no new island had been observed at the eruption site.
The activity was located near the site of an eruption reported in 1543 at 26.00°N, 140.77°E.
Geological Summary. Submarine eruption have been observed during March 1984 and August 2022-January 2023 from Kaitoku Seamount (Kaitoku Kaizan), a three-peaked submarine volcano 80 km NNW of Kita-Ioto. The type of activity related to other observations of discolored water or bubbling, including an observation from 1543 CE, is uncertain.
Information Contacts: JMA.