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). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 13:9. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198809-242050.
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.
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, Laboratoire de Géophysique, (LDG) Tahiti.