Report on Ambrym (Vanuatu) — 20 November-26 November 2024
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 20 November-26 November 2024
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2024. Report on Ambrym (Vanuatu) (Sennert, S, ed.). Weekly Volcanic Activity Report, 20 November-26 November 2024. Smithsonian Institution and US Geological Survey.
Ambrym
Vanuatu
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 eruptive activity at Ambrym during October and November. In October small steam emissions from both Benbow and Marum craters were visible in webcam images. A low-level thermal anomaly over the volcano was detected in satellite images on 3 October indicating the presence of lava at or near the surface. Low-to-moderate thermal anomalies were identified in satellite images during 1, 2, 5, and 11-12 November. Seismic data confirmed an ongoing volcanic activity. On 12 November interferometry analysis of satellite data indicated magma movement beneath the surface. The Alert Level remained at 2 (on a scale of 0-5). 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 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.
Source: Vanuatu Meteorology and Geohazards Department (VMGD)