Report on Monowai (New Zealand) — September 1990

Bulletin of the Global Volcanism Network, vol. 15, no. 9 (September 1990)
Managing Editor: Lindsay McClelland.

Monowai (New Zealand) T-waves suggest shallow volcanic activity

Please cite this report as:

Global Volcanism Program, 1990. Report on Monowai (New Zealand). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 15:9. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN199009-242050.

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Monowai

New Zealand

25.887°S, 177.188°W; summit elev. -132 m

All times are local (unless otherwise noted)


Acoustic T-waves of long duration and emergent form were recorded 30 May-18 June and 5-7 September by the Sismique Polynésien RSP large-aperture seismic network centered on Tahiti. The signals, typical of shallow submarine eruptions, originated in the vicinity of Monowai Seamount ...

Geologic Background. Monowai, also known as Orion seamount, rises to within 100 m of the sea surface about halfway between the Kermadec and Tonga island groups. The volcano lies at the southern end of the Tonga Ridge and is slightly offset from the Kermadec volcanoes. Small parasitic cones occur on the N and W flanks of the basaltic submarine volcano, which rises from a depth of about 1500 m and was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology. A large 8.5 x 11 km wide submarine caldera with a depth of more than 1500 m lies to the NNE. Numerous eruptions from Monowai have been detected from submarine acoustic signals since it was first recognized as a volcano in 1977. A shoal that had been reported in 1944 may have been a pumice raft or water disturbance due to degassing. Surface observations have included water discoloration, vigorous gas bubbling, and areas of upwelling water, sometimes accompanied by rumbling noises.

Information Contacts: J. Talandier, LDG, Tahiti.