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Report on Monowai (New Zealand) — September 1988


Scientific Event Alert Network Bulletin, vol. 13, no. 9 (September 1988)
Managing Editor: Lindsay McClelland.

Monowai (New Zealand) Shallow submarine eruption

Please cite this report as:

Global Volcanism Program, 1988. Report on Monowai (New Zealand) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 13:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198809-242050


New Zealand

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

All times are local (unless otherwise noted)

A shallow submarine eruption from Monowai was detected by Polynesian Seismic Network (Réseau Sismique Polynésien, or RSP) stations (2,800 and 4,300 km from the volcano) on [9 September from 0950 until 1820]. Acoustic T-waves, generated from lava/seawater interaction, indicated an eruption of fluctuating intensity without explosions. RSP stations recorded seismic activity from Monowai in April 1977, January 1980, May 1982, and June 1986.

Geological Summary. Monowai, also known as Orion seamount, is a basaltic stratovolcano that rises from a depth of about 1,500 to within 100 m of the ocean surface about halfway between the Kermadec and Tonga island groups, at the southern end of the Tonga Ridge. Small cones occur on the N and W flanks, and an 8.5 x 11 km submarine caldera with a depth of more than 1,500 m lies to the NNE. Numerous eruptions have been identified using 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. It was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology.

Information Contacts: J. Talandier, Laboratoire de Géophysique, (LDG) Tahiti.