An "underwater explosion" and "pumice swirl" ~30 km wide were reported at 19.10°S, 175.41°E (200 km SW of Nadi, Fiji) on 16 October at 1058 from Air Pacific flight 914 (Nadi to Sydney, Australia). At 1450, the crew of a second Air Pacific flight (enroute from Auckland, New Zealand) noted pumice visible in the sea 130 km from Nadi (on the W coast of Fiji's largest island, Viti Levu) [see also 15:11-12].

Although no historical volcanism has been reported near the observation site, the area is near a spreading center described by Gill and Whelan (1989). Another possible source of the pumice is Monowai Seamount (25.92°S, 177.15°W), 1,100 km to the ESE, where submarine activity was observed from the HMNZS Tui on 13 August. On 30 May-18 June and 5-7 September, the Polynesian Seismic Net recorded T-phase activity, centered in the Monowai area, that had characteristics typical of shallow submarine eruptions.

Reference. Gill, J., and Whelan, P., 1989, Early rifting of an oceanic island arc (Fiji) Produced shoshonitic to tholeiitic basalts: JGR, v. 94, no. B4, p. 4561-4578.

Geological Summary. Reports of floating pumice from an unknown source, hydroacoustic signals, or possible eruption plumes seen in satellite imagery.

Information Contacts: J. Latter, DSIR Geophysics, Wellington.