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Report on Gaua (Vanuatu) — September 1996


Bulletin of the Global Volcanism Network, vol. 21, no. 9 (September 1996)
Managing Editor: Richard Wunderman.

Gaua (Vanuatu) Large steam-and-gas plume observed in mid-July

Please cite this report as:

Global Volcanism Program, 1996. Report on Gaua (Vanuatu) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 21:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199609-257020



14.281°S, 167.514°E; summit elev. 729 m

All times are local (unless otherwise noted)

Activity observed during 14-15 July consisted of a large steam-and-gas plume with a strong SO2 odor. Numerous fumarolic zones covered with yellow sulfur deposits dotted the interior wall of the crater. Fairly strong degassing was taking place from the NW part of the depression. An active fumarole rose from the high interior N part of the crater (T = 119 ± 5°C). The dominant vent sent a plume W from the caldera. The highest temperature of the hot sub-lacustrine fumaroles in the NE part of the lake, in the vicinity of the seismic station, varied between 34 and 65°C. The northernmost attained a temperature of 62°C.

The cone that dominates the NW part of the caldera is composed of five principal craters. The bottom of the northernmost crater is occupied in part by a small shallow pool of greenish water. The active crater is situated on the SE flank of the cone (Mt. Garat).

Geological Summary. The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; littoral cones were formed where these lava flows reached the ocean. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. The active Mount Garet (or Garat) cone in the SW part of the caldera has three pit craters across the summit area. Construction of Garet and other small cinder cones has left a crescent-shaped lake. The onset of eruptive activity from a vent high on the SE flank in 1962 ended a long period of dormancy.

Information Contacts: Henry Gaudru, C. Pittet, C. Bopp, and G. Borel, Société Volcanologique Européenne, C.P. 1, 1211 Genève 17, Switzerland (URL: http://www.sveurop.org/); Michel Lardy, Centre ORSTOM, B.P. 76, Port Vila, Vanuatu.