The Vanuatu Meteorology and Geohazards Department (VMGD) reported ongoing unrest at Ambrym during the month of July. Field observations and webcam images from 11 and 14 July confirmed continuous degassing at Marum crater. Low-level thermal anomalies were detected in satellite imagery from 14 and 27 July. Seismic data further confirmed ongoing unrest. The Alert Level remained at 2 (on a scale of 0-5). VMGD warned the public to stay outside the Permanent Exclusion Zone, which includes a 1-km radius around Benbow Crater, and Danger Zone A, a 2-km radius around Marum Crater (including Maben-Mbwelesu, Niri-Mbwelesu, and Mbwelesu), and to stay 500 m away from the ground cracks created by the December 2018 eruption.

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: Vanuatu Meteorology and Geohazards Department (VMGD)