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Feedbacks between structural development, eruption style and output rates at Anak Krakatau, Indonesia

Kerys Meredew 1, Sebastian F.L. Watt 1, Michael Cassidy 1, Achmad Fakhrus Shomim 2, Muhammad Edo Marshal Nurshal 3, Mirzam Abdurrachman 3, Muhammad Hanif 2, Samantha L. Engwell 4, Victoria C. Smith 5, Chiara M. Petrone 6 and Carl T.E Stevenson.

  • Affiliations: 1 School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK; 2 Research Center for Geological Disaster, Research Organization for Earth Sciences and Maritime, National Research and Innovation Agency - BRIN, Indonesia; 3 Petrology, Volcanology, and Geochemistry Research Group, Department of Geological Engineering, Bandung Institute of Technology, Bandung, Indonesia; 4 British Geological Survey, The Lyell Centre, Edinburgh, UK; 5 Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford, UK; 6 The Natural History Museum, Volcano Petrology Group, London, UK. 

  • Presentation type: Talk

  • Presentation time: Thursday 11:15 - 11:30, Room R280

  • Programme No: 2.2.4

  • Theme 2 > Session 2

Abstract

Edifice destabilisation is a common volcanic process and although relatively infrequent, large-scale gravitational collapses can occur across all volcano-tectonic settings. Growing evidence suggests that cycles of edifice growth and destruction, through variable loading of the underlying magma reservoir, influence magma storage conditions and eruptive behaviour on a range of timescales. However, difficulties developing high-resolution reconstructions of activity surrounding volcanic collapse limit our understanding of these relationships.  In December 2018, Anak Krakatau underwent a major structural failure of its south-western flank. Unlike most historical lateral collapses, this failure occurred just 91 years after the volcano emerged above sea-level in 1927. As a result, Anak Krakatau offers a uniquely well-documented record of a complete cycle of edifice construction, failure and subsequent regrowth.  This work exploits this high-resolution documentation, using remote sensing techniques to generate a time series of 3D island reconstructions to analyse Anak Krakatau's volumetric output at 34 points. Results indicate a two-stage output cycle before the 2018 collapse, differentiated by an abrupt decrease in output rate coinciding with both a shift in eruptive style and increase in vent height. Following collapse, Anak Krakatau entered a new accelerated regrowth phase, with 4-years of rapid volumetric increase equivalent to 62-years of historical growth (1950-2012). By employing additional petrographic studies of tephra from five key stages through this cycle, we further investigate this coupled relationship between structural development, magma storage conditions and output rates. This is important in understanding edifice collapse at other volcanoes globally and constraining future stability at Anak Krakatau itself.