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Magma storage timescales prior to the 1883 Krakatau eruption

Adrien J. Mourey1, Euan J.F. Mutch1,2, Mike Cassidy3,4

  • Affiliations: 1Earth Observatory of Singapore, Nanyang Technological University (NTU), Singapore 2Asian School of the Environment, NTU, Singapore 3Department of Earth Sciences, University of Oxford, Oxford, UK 4School of Geography, Earth and Environmental Science, University of Birmingham, Birmingham, UK

  • Presentation type: Poster

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

  • Poster Board Number: 63

  • Programme No: 1.2.8

  • Theme 1 > Session 2

Abstract

The 1883 eruption of Krakatau, located in Indonesia, is recognized as one of the most significant explosive volcanic events in recorded history, classified with a Volcanic Explosivity Index (VEI) of 6. This climactic eruption generated an estimated volume of 18 to 21 km³ of pyroclastic density currents (PDCs), resulting in approximately 36,000 fatalities due to the associated tsunamis and ash fallout. In this work, we employed plagioclase crystals as a proxy to elucidate the long-term thermochemical evolution of the Krakatau volcanic system leading up to the eruption. The major and trace element compositions of these crystals were analyzed using Electron Probe Microanalysis (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), respectively. The plagioclase crystals extracted from PDC deposits exhibited a diverse compositional range, spanning from An38 to An92. Our findings suggest that plagioclase crystals with high-An cores are subjected to prolonged storage and re-equilibration processes within more evolved melts, leading to lower magnesium content over time scales ranging from 103 to 105 years prior to their final ascent and eruption. Magma storage timescales exceed the timescales from the previous large eruptive episode (thought to be ~540s AD), so these crystals/magma batch would have 'survived' (stayed in the reservoir) for this large eruption. Furthermore, we compared magma ascent rates across different phases of the eruption to assess their correlation with varying eruptive styles. This comprehensive analysis contributes to a deeper understanding of the pre-eruptive conditions and dynamics that characterized the Krakatau system prior to its catastrophic eruption.