In September Ambae volcano started to wake up and the VMGD raised the Volcanic Alert Level for the volcano to Level 3.
It was not clear how the eruption would develop. The volcano then entered in to an explosive phase, building a tuff cone in the lake. Some of the larger events generated tall eruption columns above the island and local ash falls. This was expected activity, based on the historic activity seen at this volcano.
The eruptions in mid-September 2017 are the same as those in 2005, the same type of eruptions were seen this time as in 2005. Some parts of the island experienced ashfalls from this type of eruption.
The style of the eruption then changed around 22 September when Geohazards staff observed lava at the surface for the first time. This was a significant change and raised the level of uncertainty about the development of the eruption. The volcanic Alert Level was also raised further at that time. The implication of lava reaching the surface was not clear.
Observation flights on Saturday, 30th of September and Sunday, October 1, 2017 show that the activity at the volcano is only happening in one of the summit crater lakes (Lake Voui). Photographs and thermal infrared images taken during observation flights show the activity consists of explosions and ejection of hot rocks, similar to what is seen and experienced at Yasur on Tanna Island. The local population could hear some of the explosions and see glow over the mountain at times.
Satellite data and the observation flights now confirm there are small lava flows on the new volcanic island. They are reaching the lake. There is a small scoria cone also on the island and the number of vents can change daily. In the last 3 days this has ranged from 2 to 4 vents. This is very normal for a small scoria cone.
The VMGD staff are able to view data from two seismic stations on Ambae and a web camera (http://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano). These transmit data 24 hours a day. The seismic activity reflects the new lava moving through the volcano and the lava reacting and mixing with the geothermal system (hence a slight increase). The seismic data does not show a large and sharp increase in activity at Ambae volcano. Scientists from VMGD will keep monitoring closely the activity, both remotely from Port Vila, thanks to a network of instruments on Ambae, and on the island as needed.
Ambae volcano is a very large volcano and is frequently active. In the recorded history there have been many eruptions, every 10-50 years and similar explosive activity every 100 to 150 years. All have been from the summit craters, except one recorded in 1670’s when a lava flow occurred near Ndui Ndui village. The current eruption is focused in the summit crater, there are no indications of activity elsewhere on Ambae Island.
The new observations on the 30th of September and 1st of October confirmed that the situation is not developing further. As the activity is now more settled and focused only on the new island in Lake Voui, the possibility of a large eruption affecting the whole island is now looking less likely.
The VMGD will continue to provide updates to the public and government as the situation evolves.