Report on Gaua (Vanuatu) — 14 August-20 August 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 August-20 August 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Gaua (Vanuatu). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 August-20 August 2013. 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 August the Vanuatu Geohazards Observatory reported that [volcanic tremor] at Gaua had increased [slightly] since June.... The Alert Level remained at 1 (on a scale of 0-4) [and ash plumes remained likely]. [The last clear report of ash emission was in October 2011. Steam plumes were observed from aircraft on 29 April and from the International Space Station on 31 May 2013.]
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.