In May, the RSP recorded seismicity from renewed eruptive activity at Macdonald. Its eight previous eruptions had begun with explosive events, but the May activity did not, and probably was a continuation of the March eruption. Reconaissance by a Marine National Française vessel did not show a perceptible increase in the volcano's summit altitude since the bathymetric survey of February 1982.

Further Reference. Talandier, J. and Okal, E.A., 1984, New Surveys of Macdonald Seamount Following Volcanoseismic Activity, 1977-1983; Geophysical Research Letters, v. 1, no. 9, p. 813-816.

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, Lab. de Géophysique, Tahiti.