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Front. Earth Sci. | doi: 10.3389/feart.2018.00223

Complex and cascading triggering of submarine landslides and turbidity currents at volcanic islands revealed from integration of high-resolution onshore and offshore surveys

 Michael A. Clare1*, Tim Le Bas1,  David Price1, 2, James Hunt1,  David Sear2,  Matthieu J. Cartigny3, Age Vellinga2, William Symons2, Christopher Firth4 and  Shane J. Cronin5
  • 1National Oceanography Centre, United Kingdom
  • 2University of Southampton, United Kingdom
  • 3Durham University, United Kingdom
  • 4Macquarie University, Australia
  • 5University of Auckland, New Zealand

Submerged flanks of volcanic islands are prone to hazards including submarine landslides that may trigger damaging tsunamis and sediment-laden seafloor flows (called ‘turbidity currents’). These hazards can break seafloor infrastructure which is critical for global communications and energy transmission. Small Island Developing States are particularly vulnerable to these hazards due to their remote and isolated nature, small size, high population densities and weak economies. Despite their vulnerability, few detailed offshore surveys exist for such islands, resulting in a geohazard ‘blindspot’, particularly in the South Pacific. Understanding how these hazards are triggered is important; however, pin-pointing specific triggers is challenging as most studies have been unable to link continuously between onshore and offshore environments, and focus primarily on large-scale eruptions with sudden production of massive volumes of sediment. Here we focus on an area with a high volcanic sediment supply, which is also similar to locations (volcanic or not) where human-induced vegetation change over-supplies sediments to coastal margins. We address these issues by integrating the first detailed (2 m x 2 m) bathymetry data acquired from Tanna Island, Vanuatu with a combination of terrestrial remote sensing data, onshore and offshore sediment sampling, and documented historical events. Mount Yasur on Tanna has experienced low-magnitude Strombolian activity for at least the last 600 years. We find clear evidence for submarine landslides and turbidity currents, yet none of the identified triggers are related to major volcanic eruptions, in contrast to conclusions from several previous studies. Instead we find that cascades of non-volcanic events (including outburst floods with discharges of >1000 m3/s, and tropical cyclones), that may be separated by decades, are more important for preconditioning and triggering of landslides and turbidity currents in oversupplied sedimentary regimes such as at Tanna. We conclude with a general model for how submarine landslides and turbidity currents are triggered at volcanic and other heavily eroding mountainous islands. Our model highlights the often-ignored importance of outburst floods, non-linear responses to land-use and climatic changes, and the complex interactions between a range of coastal and tectonic processes that may overshadow volcanic regimes.

Keywords: Cascading hazards, Turbidity current, submarine landslide, tropical cyclone, Outburst flood, Volcanic island, crescentic bedforms, Strombolian volcano

Received: 19 Sep 2018; Accepted: 21 Nov 2018.

Edited by:

Ivar Midtkandal, University of Oslo, Norway

Reviewed by:

Gijs A. Henstra, University of Bergen, Norway
Miquel Poyatos Moré, University of Oslo, Norway  

Copyright: © 2018 Clare, Le Bas, Price, Hunt, Sear, Cartigny, Vellinga, Symons, Firth and Cronin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Michael A. Clare, National Oceanography Centre, Southampton, United Kingdom, michael.clare@noc.ac.uk