An eruption was detected by acoustic waves (T-phase) received by RSP stations 6-7 July. Explosions began around 0100 on 6 July and were followed by continuous noise of variable level, with episodes of stronger intensity. The 27.5 hour crisis [but see 12:09] was . . . comparable to the November 1980 eruption in duration and intensity.

Geological Summary. Discovered by the detection of teleseismic waves in 1967, Macdonald seamount (also known as Tamarii seamount) rises from a depth of about 1,800 m to within 27 m of the ocean surface at the eastern end of the Austral Islands. The basaltic submarine volcano marks the site of a hotspot that was the source of the Austral-Cook island chain. The summit, named after volcanologist Gordon Macdonald, consists of a flat plateau about 100 x 150 m wide with an average depth of about 40 m. The summit plateau is capped with spatter cones that form steep-sided pinnacles. Most eruptions have been seismically detected, but in 1987 and 1989 pumice emission was observed from research vessels. Pumice rafts observed in the South Pacific in 1928 and 1936 may also have originated here.

Information Contacts: J. Talandier, LDG Tahiti.