Are submarine landslides an underestimated hazard on the western North Atlantic passive margin?

Alexandre Normandeau,Kimberley A Jenner,D Calvin Campbell,David J.W Piper

doi:10.1130/g46201.1

Alexandre Normandeau, Kimberley A Jenner + Show 2 more

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https://doi.org/10.1130/g46201.1

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Journal: Geology	Publication Date: Jul 10, 2019
Citations: 13	License type: cc-by

Affiliation: Geological Survey of Canada, Natural Resources Canada

Abstract

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.

Highlights

Submarine landslides are ubiquitous on theNorth Atlantic seafloor, and have potential societal impacts on public safety, the environment and the economy
Urlaub et al (2013) observed significantly fewer landslides in the Late Holocene compared to the Late Pleistocene and Early Holocene, suggesting a decreased risk for coastal populations and submarine infrastructure (Chaytor et al, 2009; ten Brink et al, 2014)
Our study shows that four large landslide events occurred offshore eastern Canada since 4 ka, sourced from a giant channel levee on the lower slope and from the upper slope

Summary

Introduction

Submarine landslides are ubiquitous on theNorth Atlantic seafloor, and have potential societal impacts on public safety, the environment and the economy. Urlaub et al (2013) observed significantly fewer landslides in the Late Holocene compared to the Late Pleistocene and Early Holocene, suggesting a decreased risk for coastal populations and submarine infrastructure (Chaytor et al, 2009; ten Brink et al, 2014). In the western North Atlantic, the largest known Holocene submarine landslide was triggered by the C.E. 1929 Grand Banks M7.2 earthquake (Kuenen, 1952). This earthquake, and subsequent submarine landslide, generated a tsunami that killed 28 people (Ruffman and Hann, 2001). The widespread 1929 event is considered a rare event in the Holocene, since other documented Holocene landslides are smaller and confined to regions of the Scotian margin cut by steep-walled canyons (Piper, 2005; Jenner et al, 2007)

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