Submarine landslide megablocks show half of Anak Krakatau island failed on December 22nd, 2018

J. E. Hunt*, D. R. Tappin, S. F.L. Watt, S. Susilohadi, A. Novellino, S. K. Ebmeier, M. Cassidy, S. L. Engwell, S. T. Grilli, M. Hanif, W. S. Priyanto, M. A. Clare, M. Abdurrachman, U. Udrekh

*Corresponding author for this work

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Abstract

As demonstrated at Anak Krakatau on December 22nd, 2018, tsunamis generated by volcanic flank collapse are incompletely understood and can be devastating. Here, we present the first high-resolution characterisation of both subaerial and submarine components of the collapse. Combined Synthetic Aperture Radar data and aerial photographs reveal an extensive subaerial failure that bounds pre-event deformation and volcanic products. To the southwest of the volcano, bathymetric and seismic reflection data reveal a blocky landslide deposit (0.214 ± 0.036 km3) emplaced over 1.5 km into the adjacent basin. Our findings are consistent with en-masse lateral collapse with a volume ≥0.175 km3, resolving several ambiguities in previous reconstructions. Post-collapse eruptions produced an additional ~0.3 km3 of tephra, burying the scar and landslide deposit. The event provides a model for lateral collapse scenarios at other arc-volcanic islands showing that rapid island growth can lead to large-scale failure and that even faster rebuilding can obscure pre-existing collapse.

Original languageEnglish
Article number2827
Number of pages15
JournalNature Communications
Volume12
Issue number1
Early online date14 May 2021
DOIs
Publication statusPublished - Dec 2021

Bibliographical note

Funding Information:
The authors thank the crew and technicians from OC Enviro, led by Ahmad Safii Maarif, for acquiring and processing the marine data. J.E.H. and M.A.C. recognise the National Environmental Research Council (NERC) Urgency Grant NE/T002034/1 “Failure mechanism and tsunamigenesis of the Anak Krakatau landslide on 22 December 2018”. S.W., M.C., S.E. and M.A. acknowledge NERC Urgency Grant NE/T002026/1 “Interactions between eruptive and sector collapse at Anak Krakatau, Indonesia”. D.R.T., S.D., S.E., A.N., S.G. and S.W. acknowledge NSFGEO-NERC Grant NE/S003509/1, “Tsunamis from large volume eruptions,” that underpinned the Anak Krakatau research through its geographic focus on the Krakatau caldera. S.G. acknowledges NSF-GEO project GEO-17-56665 that has underpinned work on Krakatau and the Anak Krakatau landslide-tsunami. S.K.E. acknowledges a NERC Independent Research Fellowship and is associated to the NERC-BGS Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET). COSMO-SkyMed (C.S.K.) data have been provided by the Italian Space Agency through the Committee on Earth Observation Satellite’s Earth Observation (CEOS)’s Volcano Demonstrator. Support from Institut Teknologi Bandung, Grant P3MI 2020 is acknowledged by M.A. that funded contributions to the marine and island surveys. The authors would like to acknowledge the funding to the Indonesian Institute of Sciences (LIPI) to complete the 2017 seismic survey. The authors would also like to thank: Professor Wahyoe Hantoro who led the 2017 seismic survey and made the data available for this study; the panel at Kementerian Riset dan Teknologi/ Badan Riset dan Inovasi Nasional Republik Indonesia (RISTEK-BRIN) who advised on our proposal towards obtaining research permits; Dr. Willem Huiskamp and the Netherlands Institute of Military History for provision of the excellent photographs of Anak Krakatau in 1949 taken during his father’s (Ben Huiskamp) flights as a military pilot in Indonesia with the Royal Netherlands Air Force; and Dr. Raphael Paris for sharing topographic data. D.R.T., S.E. and A.N., publish with the permission of the CEO of the British Geological Survey (United Kingdom Research and Innovation). The authors would like to thank and acknowledge photographers Nurul Nidayat, Didik Heriyanto, Dicky Adam Sidiq, Oystein Lund Andersen, James Reyonds and the Indonesian Nature Film Society for provision of images for use within the study. The authors would also like to acknowledge the input and discussions with Professor Simon Day.

Publisher Copyright:
© 2021, The Author(s).

ASJC Scopus subject areas

  • General Chemistry
  • General Biochemistry,Genetics and Molecular Biology
  • General Physics and Astronomy

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