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Report on Ambrym (Vanuatu) — March 2004

Bulletin of the Global Volcanism Network, vol. 29, no. 3 (March 2004)
Managing Editor: Richard Wunderman.

Ambrym (Vanuatu) Abundant MODIS thermal alerts during March 2003-February 2004

Please cite this report as:

Global Volcanism Program, 2004. Report on Ambrym (Vanuatu). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 29:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200403-257040.

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

All times are local (unless otherwise noted)

Ambrym was last reported in BGVN 28:09, when details of activity observed during September 2003 visits were published. A daily summary of MODIS thermal alerts for the year ending February 2004 (table 1) suggests, subject to the limitations of thermal imaging (e.g. in times of heavy cloud), regular activity over the course of the year. No corroborative reports of activity have been received from the [Départment de la Géologie, des Mines et des Ressources,] or the Darwin Volcanic Ash Advisory Centre.

Table 1. Nights on which MODIS thermal alerts were recorded for Ambrym, for the year ending February 2004 . Thermal alerts recorded in daylight hours have been omitted for data reliability reasons (four cases). Data courtesy HIGP MODIS Thermal Alert System.

Month Days with Thermal Alerts
Mar 2003 7, 21, 30
Apr 2003 15, 17
May 2003 1, 3, 17, 19, 20, 28
Jun 2003 9, 15, 16, 29
Jul 2003 29
Aug 2003 21, 25
Sep 2003 13, 15, 24
Oct 2003 1, 3, 8, 10, 22, 24, 31
Nov 2003 2
Dec 2003 25, 27
Jan 2004 7, 9, 12, 28
Feb 2004 1, 3, 4, 10, 17, 19, 22, 28

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.

Information Contacts: HIGP MODIS Thermal Alert System, Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa (URL: http://modis.higp.hawaii.edu/).