Report on Gaua (Vanuatu) — 16 December-22 December 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 December-22 December 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Gaua (Vanuatu). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 16 December-22 December 2009. Smithsonian Institution and US Geological Survey.
14.27°S, 167.5°E; summit elev. 797 m
All times are local (unless otherwise noted)
On 14 December, Vanuatu Geohazards Observatory reported that activity from Gaua during the previous month was characterized by continuous ash emissions accompanied by periodic steam emissions. Ashfall was reported in the W part of the island. Satellite imagery revealed that periods of significant gas emissions were more frequent than during November. Ash emissions during 14-18 December were thicker and darker, and possibly represented a new eruptive phase. Ash plumes continued to drift W and produce ashfall. The Vanuatu Volcanic Alert Level remained at 2 (on a scale of 0-4).
Geologic Background. 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 wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. Construction of the historically active cone of Mount Garat (Gharat) and other small cinder cones in the SW part of the caldera has left a crescent-shaped caldera lake. The symmetrical, flat-topped Mount Garat cone is topped by three pit craters. The onset of eruptive activity from a vent high on the SE flank in 1962 ended a long period of dormancy.