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TitleAre submarine landslides an underestimated hazard on the western North Atlantic passive margin?
AuthorNormandeau, AORCID logo; Campbell, D CORCID logo; Piper, D J WORCID logo; Jenner, K A
SourceGeology vol. 47, 2019 p. 1-5, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20180240
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
ProvinceNova Scotia; Eastern offshore region
NTS1SW; 10NE; 10SE; 11A; 11B
AreaScotian Slope; Laurentian Fan; Atlantic Ocean; Shortland Canyon
Lat/Long WENS -59.0000 -54.0000 45.0000 40.6667
Subjectsmarine geology; surficial geology/geomorphology; geophysics; Holocene; continental margins; continental slope; landslides; slope stability; slope failures; turbidity currents; geophysical surveys; acoustic surveys, marine; bathymetry; seismic interpretations; marine sediments; landslide deposits; turbidites; muds; sands; marine sediment cores; geological history; glacial history; depositional history; sedimentation rates; sedimentary structures; tsunami; core analysis; bulk density; shear strength; geophysical logging; magnetic susceptibility; North Atlantic Margin; colluvial and mass-wasting deposits; Infrastructures; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; geophysical images; seismic profiles; profiles; lithologic sections; geophysical logs; geochronological charts
ProgramPublic Safety Geoscience Marine Geohazards
Released2019 07 10
AbstractThe western North Atlantic passive margin is considered relatively stable, with few slope instabilities recognized during the Holocene. However, new multibeam bathymetry mapping and sediment core acquisition off eastern Canada indicate that previously unidentified, large, submarine landslide events occurred during the Late Holocene, between 4 and 1.5 ka. The recognition of these new gravitational events, in addition to the well-known C.E. 1929 Grand Banks earthquake-induced landslide, indicates that approximately one large landslide event per 1000 years has occurred offshore eastern Canada within the past 4000 years, a much shorter recurrence interval than hitherto reported. This Late Holocene recurrence rate is also similar to active margins around the world and is likely due to the under-consolidation and resultant instability of Scotian Slope sediments attributable to high glacial sedimentation rates. The discovery of these new Late Holocene landslides was made possible through detailed examination of cores recovered from the lower slope. These results demonstrate that submarine landslide hazard has been underestimated on the western North Atlantic margin - home to significant submarine infrastructure and proximal to a large coastal population.
Summary(Plain Language Summary, not published)
The North Atlantic seafloor is considered relatively stable, with slopes having experienced very little instabilities during the Holocene. However, new multibeam bathymetry mapping conducted on the passive eastern Canadian margin along with the collection of sediment cores have allowed the identification of three new large submarine landslides that have occurred during the late-Holocene, between 4 and 1.5 ka BP. The discovery of these new late-Holocene landslides demonstrate that the risk they pose has been largely underestimated in the North Atlantic deep-waters, where submarine infrastructure such as submarine cables are present.

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