On the timing and nature of the multiple phases of slope instability on eastern Rockall Bank, Northeast Atlantic

One of the most challenging tasks when studying large submarine landslides is determining whether the landslide was initiated as a single large event, a chain of events closely spaced in time or multiple events separated by long periods of time as all have implications in risk assessments. In this study we combine new multichannel seismic profiles and new sediment cores with bathymetric data to test whether the Rockall Bank Slide Complex is the composite of multiple slope collapse events and, if so, to differentiate them. We conclude that there have been at least three voluminous episodes of slope collapse possibly separated by long periods o...  more

One of the most challenging tasks when studying large submarine landslides is determining whether the landslide was initiated as a single large event, a chain of events closely spaced in time or multiple events separated by long periods of time as all have implications in risk assessments. In this study we combine new multichannel seismic profiles and new sediment cores with bathymetric data to test whether the Rockall Bank Slide Complex is the composite of multiple slope collapse events and, if so, to differentiate them. We conclude that there have been at least three voluminous episodes of slope collapse possibly separated by long periods of slope stability, a fourth, less voluminous event, and a possible fifth more localized event. The oldest event is estimated to be several hundred thousand years old. The second event took place at the same location as slide A, reactivating the same scar, nearly 200 ka ago. Slide C, the most voluminous event, took place 22 ka ago and initiated further north from the other slides. Slide D was of a much smaller event is that happened 10 ka ago while the most recent event, albeit very small-scale, took place within the last 1000 years. This study highlights the need to thoroughly investigate large slide complexes to evaluate the event sequencing as seismic studies may hide multiple small-scale events. It also reveals that the same slide scarps can be reactivated and generate slides with different flow behaviors. This paper has been submitted in Geochemistry, Geophysics, Geosystems.