Ingrid Ukstins, Shane Cronin and Joali Paredes Marino (University of Auckland)
The largest volcanic eruption in the past 30 years was that of the Hunga-Tonga-Hunga-Ha'apai submarine volcano in Tonga. University of Auckland researchers were the first to acquire ash samples and initiated an emergency investigation of the health impact of the ash.
In January 2022 Hunga-Tonga-Hunga-Ha'apai erupted with a column of debris that reached 39 km in height, with the overshooting top hitting 55 km. The extreme explosiveness of this eruption contrasts with the subdued gas content of the magma itself. Understanding the destructive explosivity of this eruption will help understand expected hazards during recovery efforts, and to develop realistic eruption scenarios.
Researchers used X-ray computed micro tomography (µCT) with the Imaging and Medical (IM) beamline to investigate pumice particles from the eruption. The resulting images enabled quantification of the particle morphology, and assessment of the role of magmatic volatiles and external water in driving the explosivity.
The team found that almost 20 % of the particles were smaller than 30microns, which is a hazard to helicopter flight, and more than 7% of the particles were less than 10microns, meaning that they are a health hazard to those who might breathe the ash.
As well as providing great scientific value, the quickly obtained results enabled the team to relay the hazard information directly to both New Zealand and Tongan disaster agencies.
Related research:
Torres-Orozco R, Cronin SJ, Pardo N, Kósik S, Ukstins I, Heinrich M, Lee Gpd. 2023. Complex decompression and fragmentation of mingled andesite magmas driving multi-phase Plinian eruptions at Mt. Taranaki, New Zealand. Journal of Volcanology and Geothermal Research 433: 107728. https://doi.org/10.1016/j.jvolgeores.2022.107728
