Based on pilot observations, analyses of satellite imagery, and information from the Vanuatu Geohazards Observatory, the Wellington VAAC reported that on 8 and 10 August ash-and-steam plumes from Ambrym rose to an altitude 6.1 km (20,000 ft) a.s.l. and drifted W and NW.

Geological Summary. Ambrym is a large basaltic volcano with a 12-km-wide caldera formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. 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 been frequently reported since 1774, though mostly limited to extra-caldera eruptions that would have affected local populations. Since 1950 observations of eruptive activity from cones within the caldera or from flank vents have occurred almost yearly.

Source: Wellington Volcanic Ash Advisory Center (VAAC)