The Vanuatu Meteorology and Geohazards Department (VMGD) reported ongoing unrest at Ambae during the month of July based on seismic and satellite data. Satellite imagery and webcam observations from 13, 17, 26, and 28-29 July showed continuous steam and/or gas emissions. Sulfur dioxide emissions were recorded in satellite images acquired on 1-3, 5-7, 9-16, 18-19, 22-24, 27-28, and 30 July. A low-level thermal anomaly was also detected in satellite images from 10, 23, and 28 July. The Alert Level remained at 2 (on a scale of 0-5), and the public was warned to stay outside of Danger Zone A, defined as a 2-km radius around the active vents in Lake Voui, and to stay 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.

Source: Vanuatu Meteorology and Geohazards Department (VMGD)