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Decoding Water-Magma Dynamics through Ash Analysis at Torfajökull

Catherine Brown1, Rebecca Carey1, Þorvaldur Þórðarson2

  • Affiliations: 1 School of Natural Sciences, University of Tasmania, Hobart, Australia; 2 School of Engineering and Natural Sciences, Faculty of  Earth Sciences, University of Iceland, Reykjavik, Iceland

  • Presentation type: Poster

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

  • Poster Board Number: 177

  • Programme No: 3.3.14

  • Theme 3 > Session 3

Abstract

Torfajökull, located in Iceland, is known for its complex volcanic activity, including both explosive and effusive eruptions. This study examines ash particles smaller than 4 phi from the Torfajökull volcanic system to determine the presence and extent of water-magma interactions. Understanding water-magma interactions is crucial for interpreting past volcanic events and assessing future hazards. Ash samples were collected from the 870 CE eruption deposits around Torfajökull. Particles were mounted on carbon tape and imaged with the Backscattered Electron Detector of a Zeiss FEG-SEM, in order to image particle shapes and surface textures. With MatLab tools PARTIcle Shape ANalyzer (PARTISAN) and DendroScan we analysed particle shape morphology. Specific attention was given to identifying characteristics indicative of phreatomagmatic activity, such as quenching cracks, vesicle shapes, and damage fracture abundance, type and complexity. Preliminary results indicate that a significant portion of the ash particles exhibit textures consistent with rapid cooling and fragmentation in the presence of water. These findings support the hypothesis that water-magma interactions played a substantial role in the formation of these deposits from Torfajökull. Further quantitative analysis and comparison with experimental data will refine our understanding of the processes involved. This research contributes to volcanology by providing insights into the mechanisms of explosive eruptions and the role of external water sources. The outcomes have implications for volcanic hazard assessment and risk mitigation in regions with similar volcanic systems.