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New evidence for sector collapse preceding the devastating 1883 Krakatau eruption

Morelia Urlaub1, Séverine Furst1, Christian Berndt1, Julie Christin Schindlbeck Belo1, Jens Karstens1, Michel Kühn2, Dave Tappin3, Raphael Paris4, Sebastian Watt5, James Hunt6, Thor Hansteen1, Sri Ardhyastuti7, Shofia Karima7, Aditya Pratama7, Adam Nugroho7, Elisa Klein1, Katharina Pank1, Jonas Preine8, Fiene Stoepke1, Kerys Meredew5, Janine Berndt1, Semeidi Husrin7

  • Affiliations: 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany; 2Lamont-Doherty Earth Observatory, Columbia University, US; 3British Geological Survey, Nottingham, UK; 4Laboratoire Magmas & Volcans, Université Clermont-Auvergne, France; 5University of Birmingham, UK; 6National Oceanography Centre, Southampton, UK; 7The National Agency of Research and Innovation, Bandung, Indonesia; 8Woods Hole Oceanographic Institution, Woods Hole, US

  • Presentation type: Talk

  • Presentation time: Thursday 11:00 - 11:15, Room R280

  • Programme No: 2.2.3

  • Theme 2 > Session 2

Abstract

The 1883 eruption of Krakatau remains the most catastrophic volcanic eruption in recorded history. It generated tsunami wave runup up to 40 meters high, followed by pyroclastic density currents impacting coastlines hundreds of kilometers away. Current understanding suggests that the violent climactic eruption was initiated by overpressure in the magma system and that the pyroclastic flows generated the main tsunami. New marine geophysical and geochemical data from the west of Krakatau provide evidence for a large debris avalanche deposit containing blocks up to 300 m long and wide. Seismic data and geochemical fingerprinting of tephras indicate that the debris avalanche occurred prior to the ejection of most of the eruptive material. Given the size, distribution, and distance of these blocks, the avalanche must have resulted from a high-energy event, such as sector failure. We therefore propose that the primary trigger for the large explosive eruption was a sector collapse of Krakatau, and this mechanism contributed to tsunami generation. This interpretation is consistent with previous observations, such as that the surge component of the pyroclastic density currents was directed northward to westward. Large scale mass movement and lateral failure, generating landslides, may be an under-recognised process occurring as part of caldera subsidence. Causal links between sector collapse and the triggering of catastrophic eruptions have been observed elsewhere, including Mt. St. Helens in 1980. Our results further suggest that sector collapse may be an important trigger for large explosive eruptions.