On 27 June the Vanuatu Meteorology and Geohazards Department (VMGD) reported that steam-and-gas emissions from the active vents at Ambae were ongoing during the previous month based on webcam and satellite images and field observations. Seismic data also confirmed ongoing unrest. The emissions contained ash and sulfur dioxide gas during 29-30 June based on satellite data. According to the Wellington VAAC ash plumes rose 2.4-3.4 km (8,000-11,000 ft) a.s.l. and drifted E, NE, W, and NW. Residents reported ashfall in areas downwind. The Alert Level remained at 2 (on a scale of 0-5), and the public was warned to stay outside of the Danger Zone, defined as a 2-km radius around the active vents in Lake Voui, and away from drainages during heavy rains.

Geological Summary. The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone with numerous scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Sources: Wellington Volcanic Ash Advisory Center (VAAC), Vanuatu Meteorology and Geohazards Department (VMGD)