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Nature of offshore Hunga eruption deposits and behaviour of subaqueous volcaniclastic density currents

Jacob Alexander Nash1,2 , Isobel Yeo1, Michael Clare1, James Hunt1, Andrew Cundy2, Sally Watson3, Richard Wysoczanski3, Sarah Seabrook3, Kevin Mackay3, Shane Cronin4, Joali Parades-Marino4, Taaniela Kula5, Rennie Vaiomounga5, Cían McGuire6, Miros Charidemou6.

  • Affiliations: 1Ocean BioGeoscience, National Oceanography Centre (NOC), Southampton, UK; 2 School of Ocean and Earth Science, University of Southampton, UK; 3National Institute of Water and Atmospheric Research (NIWA), Auckland, New Zealand; 4School of Environment, University of Auckland, Auckland, New Zealand; 5Ministry of Lands, Survey, Planning and Natural Resources, Nuku\'alofa, Kingdom of Tonga; 6British Ocean Sediment Core Research Facility (BOSCORF), NOC, Southampton, UK 

  • Presentation type: Talk

  • Presentation time: Tuesday 09:30 - 09:45, Room R290

  • Programme No: 6.2.5

  • Theme 6 > Session 2

Abstract

Explosive volcanism frequently occurs in marine settings where erupted pyroclastic material can enter the ocean and generate powerful subaqueous volcaniclastic density currents (SVDCs). The capacity for these density-driven currents to travel hundreds of kilometres across the seafloor and damage critical subsea infrastructure poses direct threats to remote island communities. These threats were highlighted by the January 15th, 2022, eruption of the shallow-submarine Hunga volcano, Kingdom of Tonga, where eruption triggered SVDCs damaged subsea telecommunication cables, severing Tonga from global communication. Despite their hazardous nature, understanding of density current behaviour and their seafloor impacts has been limited by a paucity of real-time observations and minimal in-situ deposits categorically linked to these currents. We address this knowledge gap with the first detailed sedimentological and geochemical characterization of the deposits of SVDCs triggered during the 2022 Hunga eruption. Using the submarine sedimentary record of this event we characterize these SVDCs and their resultant depositional signature. We show that periodic eruption-column collapse triggered multiple pulses of density-stratified currents that ran-out >117 km. Erosion and entrainment of ~3.5 km3 of material into the currents increased flow mobility, speed, and competency, enabling them to deposit coarse material 105 km from source. Through integration of well-observed subaerial eruption phenomena and post-eruption bathymetric data we contextualize the density currents within the eruption timeline. Identification of these SVDCs coupled, here, with detailed deposit characterization provides step-changes for understanding the destructive and distributive processes dispersing volcaniclastic materials across the seafloor, and the threats posed to vulnerable communities and infrastructure.