Combinations of volcanic-flank and seafloor-sediment failure offshore Montserrat, and their implications for tsunami generation


Watt, S.F.L., Talling, P.J., Vardy, M.E., Heller, V., Huhnerbach, V., Urlaub, Morelia, Sarkar, Sudipta, Masson, D.G., Henstock, T.J., Minshull, T.A., Paulatto, M., Le Friant, A, Lebas, E, Berndt, C., Crutchley, G, Karstens, J, Stinton, A and Maeno, F (2012) Combinations of volcanic-flank and seafloor-sediment failure offshore Montserrat, and their implications for tsunami generation. Earth and Planetary Science Letters, 319-320, 228-240. (doi:10.1016/j.epsl.2011.11.032).

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Description/Abstract

Recent seafloor mapping around volcanic islands shows that submarine landslide deposits are common and widespread. Such landslides may cause devastating tsunamis, but accurate assessment of tsunami hazard relies on understanding failure processes and sources. Here we use high-resolution geophysical data offshore from Montserrat, in the Lesser Antilles, to show that landslides around volcanic islands may involve two fundamentally different sources of sediment (island-flank and larger seafloor-sediment failures), and can occur in multiple stages. A combination of these processes produces elongate deposits, with a blocky centre (associated with island-flank collapse), surrounded by a smoother-surfaced deposit that is dominated by failed seafloor sediment. The failure of seafloor sediment is associated with little marginal accumulation, and involves only limited downslope motion. Submarine landslide deposits with similar blocky and smoothsurfaced associations are observed in several locations worldwide, but the complex emplacement processes
implied by this morphological relationship can only be revealed by high-resolution geophysical data. Such complexity shows that the volume of landslide deposits offshore of volcanic islands cannot simply be used in tsunami models to reflect a single-stage collapse of primary volcanic material. By applying predictive equations
for tsunami amplitude to investigate general scenarios of volcanic island landslide generation, we show that the tsunami hazard associated with volcanic island collapse remains highly significant. Volcanic flank failures, even if relatively small, may generate large local tsunamis, but associated seafloor sediment failures, even if they have a much greater volume, have a substantially lower potential for tsunami generation.

Item Type: Article
ISSNs: 0012-821X (print)
Keywords: landslide; tsunami; volcano; Montserrat; submarine sediment slide; flank collapse
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Q Science > QE Geology
Divisions: Faculty of Engineering and the Environment > Civil, Maritime and Environmental Engineering and Science
Faculty of Natural and Environmental Sciences > Ocean and Earth Science
Faculty of Natural and Environmental Sciences > Ocean and Earth Science > Geology & Geophysics
National Oceanography Centre (NERC) > Marine Geoscience
ePrint ID: 208973
Date Deposited: 24 Jan 2012 15:38
Last Modified: 27 Mar 2014 19:50
Projects:
How is ash dispersed in the ocean around volcanoes?
Funded by: NERC (NE/F010478/1)
Led by: Peter Talling
26 September 2008 to 25 April 2009
URI: http://eprints.soton.ac.uk/id/eprint/208973

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