Based on satellite data, webcam observations, and wind model data, the Wellington VAAC reported that during 21-27 March ash plumes from the vent at Ambae’s Lake Voui rose to altitudes of 3-4.6 km (10,000-15,000 ft) a.s.l. and drifted mainly S and SW, but towards the end of the week to the N and W. News articles noted that ashfall had significantly impacted the S and W parts of the island, damaging crops, contaminating water, and collapsing homes, leading to the evacuation of three villages. On 25 March a flight was cancelled. Residents of Santo reportedly witnessed incandescent material being ejected as high as 1 km around 1800 and 2200; residents also noted four more events during the next morning that were also heard in Pentecost and Maewo.

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), Radio New Zealand, Vanuatu Independent