Report on Ambrym (Vanuatu) — 3 December-9 December 2014

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 December-9 December 2014
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2014. Report on Ambrym (Vanuatu). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 December-9 December 2014. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (3 December-9 December 2014)


Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


On 8 December the Vanuatu Geohazards Observatory reported that observations and analyses of Ambrym conducted during November and early December showed that activity levels had slightly decreased. The Alert Level was lowered to 1 (on a scale of 0-4). VGO warned that the area in close proximity to the active vents (Benbow, Maben-Mbwelesu, Niri-Mbwelesu, and Mbwelesu) remained dangerous.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Source: Vanuatu Meteorology and Geo-hazards Department