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The offshore imprint of the 2008 eruption of Chaitén, Chile

Kerys Meredew1, Sebastian Watt1, Rodrigo Fernandez2, Rebecca Totten3, Guilia Matilde Ferrante4, Javier Canete5, Alastair Hodgetts6, Paola Pena7, Constanza Perales7, Ivan Sunye Puchol8, Anke Zernack9 and the FKt240902 scientific party.

  • Affiliations: 1School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK; 2Departamento de Geología, Universidad de Chile, Santiago, Chile; 3Department of Geological Sciences, University of Alabama, Tuscaloosa, USA; 4Sezione di Geofisica, OGS Trieste, Trieste, Italy; 5School of Environment, University of Auckland, Auckland, New Zealand; 6School of Geosciences University of Edinburgh, Edinburgh, UK; 7SERNAGEOMIN, Santiago, Chile; 8Dipartimento di Scienze della Terra, Sapienza University of Rome, Rome, Italy; 9School of Agriculture and Environment, Massey University, Palmerston North, New Zealand. 

  • Presentation type: Poster

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

  • Poster Board Number: 156

  • Programme No: 3.5.15

  • Theme 3 > Session 5

Abstract

The 2008 explosive eruption of Chaitén volcano (Chile) dispersed tephra across the surrounding region, forming a widespread fall deposit extending eastward across Argentina. Rainfall remobilised proximal fall deposits in the days following the eruption, rapidly funnelling material through two local drainage basins and forming lahars with terrestrial pathways of 10-15 km. The southward directed lahars inundated Chaitén town and extended the coastline through rapid accumulation of volcaniclastic sediment. A major proportion of erupted products entered the ocean via post-eruptive laharic processes, but the ultimate fate, impact and distribution of this material is unknown. Here, we report preliminary results of marine research expedition FKt240902 (Schmidt Ocean Institute; September 2024) that surveyed the region offshore Chaitén. This project investigated the impacts of the Chaitén eruption in the marine environment (and subsequent recovery), the processes dispersing volcaniclastic sediment that entered the ocean, and the potential of historic secondary volcaniclastic stratigraphies in southern Chile. The FKt240902 expedition collected extensive bathymetry and sub-bottom profiles throughout the seas west of Chaitén, providing the first high-resolution mapping of the region. Oceanographic measurements, alongside these geophysical data, demonstrate a complex glacially sculpted seafloor and current dominated regimes, strongly influencing marine tephra deposition. Remotely-operated vehicle observations and sediment cores identified deposits from Chaiten extending at least 20 km offshore, including deposits likely originating from the 2008 eruption, alongside earlier events. Initial results demonstrate strong potential for offshore records to provide high-resolution eruption histories, and a route to exploring the interaction of volcanic, climatic and environmental change in the region.