Report on Nikko (Japan) — December 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 12 (December 1990)
Managing Editor: Lindsay McClelland.
Nikko (Japan) No water discoloration seen in 1990
Please cite this report as:
Global Volcanism Program, 1990. Report on Nikko (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199012-284132.
23.078°N, 142.326°E; summit elev. -392 m
All times are local (unless otherwise noted)
No discolorations were observed at . . . Nikko . . . during 1990.
Geologic Background. Nikko submarine volcano is a massive seamount that rises from nearly 3 km depth to within 392 m of the sea surface at the SE end of a submarine ridge segment extending from Minami-Ioto island. Two large cones at the basaltic-to-andesitic volcano have been constructed on the NW and NE rims of a roughly 3-km-wide, flat-floored submarine caldera, whose rim is prominently displayed on the southern side, but largely buried on the north. A smaller cones lies on the SE caldera floor. The larger NW cone lies within a partially buried crater and displays hydrothermal activity. Discolored water was observed in July 1979, but none has been observed during semi-regular seasonal reconnaissance flights since then. Hydrothermal venting was documented during a recent NOAA expedition.
Information Contacts: Hydrographic Department, JMSA.