Following the disaster caused by Hunga Tonga-Hunga Ha’apai, Tonga Geological Services is keeping a close eye on a volcano in the island group after recent activity
A volcanic alarm has been sounded amid fears of a possible eruption close to the underwater Tongan volcano which killed several people in 2022.
Tonga Geological Services reported an increase in activity in the Tofua Island, located in the central part of the Tonga Islands group last month. Since then, it has put out daily updates amid fears of a potential eruption, with the latest including a hazard alert telling sailors to give the area a wide berth of just over one nautical mile – around 1.8km.
The warning reads: “Ongoing magmatic activities in Tofua Volcano have been indicated by fluctuations in the ground thermal levels. All Mariners are advised to sail beyond 1.08 nautical miles from Tofua Volcano until further notice. A preliminary Volcanic Hazard Map indicates the restricted zone for Tofua Volcano. The public is hereby advised to adhere to these restrictions for safety purposes. In the last 24 hours, a slight decrease in the number of events. The volcano activity poses low risk to the Vava’u and Ha’apai Communities.”
In 2022, at least seven people were killed when a 15ft tsunami slammed into the nearby island community, triggered by the underwater eruption of Hunga Tonga-Hunga Ha’apai. A later expedition examining the aftermath of the found it shifted enough rock to fill three million Olympic sized swimming pools.
Voyage leader, NIWA marine geologist Kevin Mackay, said he was completely taken aback by what they first saw. He said: “With an explosion that violent – the biggest ever recorded – you would expect the whole volcano would have been obliterated, but it wasn’t.
“While the volcano appeared intact, the seafloor showed some dramatic effects from the eruption. There is fine sandy mud and deep ash ripples as far as 50 kilometres away from the volcano, with gouged valleys and huge piles of sediment.”
The team also studied impacts on the ecosystem and found there was a boon in the amount of marine life found nearby. There was also evidence of more recent eruptions as fresh ash was discovered in the water, yet to settle on the sea floor.
NIWA biogeochemist Dr Sarah Seabrook added: “In the immediate aftermath of an eruption, volcanic ash fertilises microscopic ocean algae thanks to the ash’s concentration of nutrients and trace metals – in this case, there was a bloom of life so big we could see it from space. However, the unexpected persistence of the ash in the water column is creating prolonged impacts.
“For example, spikes in volcanic ash were coupled to the appearance of oxygen minimum zones – where oxygen levels in the water are at their lowest – which could have implications for important services provided by the ocean, such as food production and carbon sequestration.”
