Report on Ambrym (Vanuatu) — 27 April-3 May 2022
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
27 April-3 May 2022
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2022. Report on Ambrym (Vanuatu). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 27 April-3 May 2022. Smithsonian Institution and US Geological Survey.
16.25°S, 168.12°E; summit elev. 1334 m
All times are local (unless otherwise noted)
The Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that incandescence from Ambrym’s Benbow Crater was visible during 25 January-3 February from a lava flow that had effused from a new vent on the NW part of the crater floor. Recent observations indicated that gas and ash was no longer being emitted from the crater, and seismicity had decreased and stabilized. The Alert Level was lowered to 1 (on a scale of 0-5) on 28 April. VMGD warned the public to stay outside of Permanent Danger Zone A, defined as a 1-km radius around Benbow Crater and a 2-km radius around Marum Crater, and additionally to stay 500 m away from the ground cracks created by the December 2018 eruption.
Geological Summary. 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 1,900 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 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.