The latest eruption on Ambae island in Vanuatu produced more ash than last year's event, volcanologists say.
Buildings have collapsed under the weight of the ash which has also contaminated water supplies and killed food crops forcing thousands to leave their villages and seek shelter elsewhere on the island.
Listen to interview with volcanologist Brad Scott
A decision on whether or not to permanently evacuate Ambae is to be made this week by the Vanuatu Council of Ministers.
New Zealand volcanologist, Brad Scott, has been travelling back and forth to Vanuatu supporting local authorities with the monitoring of the volcano.
He said it had undergone three eruption phases since last year and the current one is the worst.
"In the first phase the volcanic island was forming in lake Voui. The second phase was more dominated by lava flows making the island larger and growing what we call a scoria cone.
"The third phase was more explosive, creating a large crater and that is where the volcanic ash was coming from that is now impacting the people on the island."