Report on Gaua (Vanuatu) — 7 April-13 April 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
7 April-13 April 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Gaua (Vanuatu). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 April-13 April 2010. Smithsonian Institution and US Geological Survey.
14.27°S, 167.5°E; summit elev. 797 m
All times are local (unless otherwise noted)
On 7 April, the Vanuatu Geohazards Observatory reported that recent field observations of Gaua confirmed significant changes in activity. Gas plumes were detected daily by satellite images. During the end of March through the beginning of April, ash plumes rose daily to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. Explosions were heard in nearby villages. Starting on 3 April villagers living in the N and S parts of the island reported ashfall and saw bombs ejected from Gaua. Based on Vanuatu Geohazards Observatory information, the Wellington VAAC reported that during 8-12 April ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. Ash plumes were seen on satellite imagery on 11 and 12 April drifting S and SE. The Vanuatu Volcano Alert Level (VVAL) remained at 2 (on a scale of 0-4).
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 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.