The source of the pumice remains unknown. Analysis of March and April records from the Réseau Sismique Polynésien (RSP) revealed no acoustic waves (T-phase) from eruptions other than that of Macdonald Seamount. However, the numerous small islands in the area of the Kermadecs, Tonga, Samoa, and Fiji interfere with acoustic waves, preventing effective T-phase monitoring of volcanic activity in some parts of the South Pacific. J. Talandier notes that measurements of surface currents in French Polynesia and similar latitudes suggest that pumice from Macdonald should drift eastward, away from the 6 April site.

Pumice came ashore at both the SE and NW ends of the Tuamoto Archipelago, on the Gambier Islands (23.15°S, 134.97°W) and at Rangiroa (15.00°S, 147.67°W), 4,800 km E and 3,900 km ESE of the 6 April observation. No information on the amount of pumice or the date of its arrival at these locations was available. Talandier noted that Rangiroa is very remote from known active volcanoes other than those in the Mehetia region, where eruptions occur at depths that are too great for production of pumice.

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

Information Contacts: J. Talandier, Lab. de Géophysique, Tahiti.