New insights into Hunga volcano eruption from ANSTO

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New analysis from an Auckland research team provides insights into why Tonga’s Hunga volcano eruption was so violent.

Internationally recognised volcanologist Professor Shane Cronin’s team at the University of Auckland worked with Australia’s Nuclear Science and Technology Organisation (ANSTO) at the Australian Synchrotron to support comprehensive research on the Hunga event.

Cronin said the eruption was the biggest of its kind in 140 years.

“We’ve never seen an eruption of this kind before,” the New Zealand volcanologist said.

“There was no warning, which had devastating consequences for Tonga and many Pacific Island countries.”

When the Hunga volcano erupted in January this year, it ejected ash and smoke that reached more than 55 kilometres into the atmosphere, causing local fatalities and evacuations. 

The blast created significant tsunami waves in the Pacific Basin and generated pressure waves that encircled the globe. This was felt even in Australia, with waves of 82cm at the Gold Coast, 65cm at Port Kembla and 77cm at Eden’s Twofold Bay in NSW.

Cronin and his team acquired very fresh samples shortly after the event, including seafloor sampling of the ocean floor undertaken by the South Korean Polar Research Institute ice breaker, Aaron.

Most of the evidence of the eruption was contained in very fine glassy particles of ash, which was previously thought to be indicative of a smaller eruption.

“Even direct magma-water contact is not enough to explain what happened with Hunga,” Cronin said.

“We think there was a magma-water interaction that was just deep enough to cause direct water magma contact in a volcano that was collapsing in on itself with lots of fractures in the sea wall, and a mixing of magma that released gas and built-up pressure.”

Two sets of experiments have already been carried out on the imaging and medical beamline and the infrared microspectroscopy beamline, while another investigation is scheduled for the X-ray fluorescence microscopy beamline.

ANSTO’s Dr Mark Tobin said the analysis would provide a better understanding of the specific chemical and mechanical processes that made the underwater volcano so uniquely destructive. 

“The infrared beamline can be very useful in geological investigations, such as analysing volcanic ash at the micron scale, by providing maps of different elemental contributions and the compositional variations of some of the most volatile elements,” Tobin said.

There are at least 10 volcanic seamounts in the wider region of the south-west Pacific that could produce something similar to the Hunga explosions on a shorter timescale.

Professor Cronin said he hoped these findings could be used to develop better prediction and early warning systems that may allow for faster, more efficient responses to volcanic and seismic activity in the Pacific.

“Understanding just how often they might have this kind of eruption with the perfect water dips and also with this kind of mingling of magma would be really important in informing risk assessments,” he said.