Report on Monowai (New Zealand) — May 2002

Bulletin of the Global Volcanism Network, vol. 27, no. 5 (May 2002)
Managing Editor: Richard Wunderman.

Monowai (New Zealand) Strong T-waves during May 2002 indicate explosive activity

Please cite this report as:

Global Volcanism Program, 2002. Report on Monowai (New Zealand). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 27:5. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN200205-242050.

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Monowai

New Zealand

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

All times are local (unless otherwise noted)


The last reported activity at Monowai occurred during June 1999 when a strong acoustic crisis was recorded (BGVN 24:06). During May 2002, strong T-waves coming from Monowai were detected by the French Polynesian Seismic Network. The signal began at 1522 on 24 May and suggested explosive activity. Several small events were detected during the next two hours. No further activity was recorded following the event.

General Reference. Davey, F.J., 1980, The Monowai Seamount: an active submarine volcanic centre on the Tonga-Kermadec Ridge (Note): New Zealand Journal of Geology and Geophysics, v. 23, p. 533-536.

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: Dominique Reymond, Geophysical Laboratory, CEA/DASE, PO Box 640, Papeete, Tahiti, French Polynesia (Email: cppt@labogeo.pf).