Skip to content

Damage Fractures as evidence of Fuel-Coolant-Interaction amplified fragmentation. Insights and comparisons from the 2022 Hunga and 1883 Krakatau eruptions.

Rachael J. M. Baxter1, James D. L. White1, Tobi Duerig2, Joali Paredes-Marino3, Shane J. Cronin3, Michael Cassidy4, Sung-Hyun Park5

  • Affiliations:  1 Department of Geology, University of Otago, Dunedin, New Zealand 2 Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland 3 School of Environment, The University of Auckland, Auckland, New Zealand 4 School of Geography, Earth and Environmental Sciences, University of Birmingham, United Kingdom 5 Division of Earth Sciences, Korea Polar Research Institute, Incheon, Republic of Korea

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 185

  • Programme No: 3.3.19

  • Theme 3 > Session 3

Abstract

The explosive eruption of Tonga's Hunga Volcano on 15 January 2022 produced a >40 km plume, damaging tsunamis in Tonga, a global meteotsunami, sea-surface pyroclastic density currents, and eruption-fed submarine density currents. We analysed damage fractures on 4 phi (63-88 micron) ash particles from both submarine and subaerial deposits of the 2022 Hunga eruption and compared them with samples from the climatic phase of the 1883 Krakatau eruption. Particles were mounted on carbon tape and high resolution, high magnification images were captured using the Backscattered Electron Detector of a Zeiss FEG-SEM. Damage fracture analysis provides insight into energy expenditure during fragmentation. Greater energy expenditure increases fracture abundance, while increased density of energy expended creates more-complex damage fractures. Using a Damage Fracture Intensity (DFI) index---accounting for fracture prevalence, relief, complexity, and interactions with glass-crystal boundaries---we find up to 83% of particles from Hunga samples exhibit severe to extreme damage. This significantly exceeds the 19--34% observed for the climatic phase of Krakatau, and lower fractions yet for many other eruptions. Damage fracture intensities as high as Hunga's have only been documented for particles created by fuel-coolant-interaction (FCI) experiments. The very high abundance and complexity of fractures on Hunga particles indicate that very high densities of energy were expended during fragmentation. We infer from this that intense magma-water interaction of fuel-coolant type produced these fractures, which provide a physical record of the extreme fragmentation processes that characterised one of the most powerful explosive eruptions ever recorded.