Report on Macdonald (Undersea Features) — April 1984
Scientific Event Alert Network Bulletin, vol. 9, no. 4 (April 1984)
Managing Editor: Lindsay McClelland.
Macdonald (Undersea Features) Renewed submarine activity in 1983
Please cite this report as:
Global Volcanism Program, 1984. Report on Macdonald (Undersea Features). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 9:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198404-333060.
28.98°S, 140.25°W; summit elev. -39 m
All times are local (unless otherwise noted)
Between May 1983 and January 1984, the RSP recorded acoustic waves (T-phase) from three shallow submarine eruptions at Macdonald Seamount. On 17 May 1983, eruptive activity began gradually with a few explosive sequences and lasted 4.5 days until 21 May. Activity resumed explosively on 27-28 October and continued for 15 hours with numerous explosive sequences. On 24 December, activity began gradually with no explosive sequences and continued for almost 10 days until 3 January 1984. This last event was the 12th and longest eruption recorded since the volcano was discovered in 1967.
Geologic Background. Discovered by the detection of teleseismic waves in 1967, Macdonald seamount (also known as Tamarii seamount) rises from a depth of about 1800 m to within 27 m of the sea surface at the eastern end of the Austral Islands. The alkali-basaltic submarine volcano marks the site of a hotspot that was the source of the Austral-Cook island chain. The summit of the seamount, 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.