On 18 March the Vanuatu Geohazards Observatory (VGO) reported that eruptive activity at Ambae’s Lake Voui during February-March was similar to activity observed at the end of October 2017, but with more sustained ash emissions from explosions at the vent. The ongoing ash-and-gas emissions were impacting local villages, prompting VGO to raise the Alert Level to 3 (on a scale of 0-5) and to warn residents and tourists to stay outside of the Danger Zone defined as a 3-km radius around the active vent in Lake Voui. A news article noted that ashfall was reported in the NW, W, SW, and S parts of the island.

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: Vanuatu Meteorology and Geohazards Department (VMGD), Radio New Zealand