Submarine landslides can be important mechanisms for transporting sediment down sloping seabeds. They occur when stresses acting downslope exceed the available strength of the seabed sediments. Landslides occur preferentially in particular environments, including fjords, active river deltas, submarine canyons, volcanic islands and, to a lesser extent, the open continental slope. Evaluating the relative stability of different seabeds requires an understanding of driving stresses and sediment strength. Stresses can be caused by gravity, earthquakes and storm waves. Resisting strength can be reduced by pore water and gas pressures, groundwater seepage, rapid sediment deposition, cyclic loading and human activity. Once slopes have become unstable or have failed, strength may continue to decrease, leading to sediment debris flows and possibly turbidity currents. Recent submarine landslide research has: shown that landslides and sediment waves may generate similar deposits, which require careful interpretation; expanded our knowledge of how strength develops in marine sediment; improved techniques for predicting sediment rheology; and developed methodologies for mapping and predicting the medium-to large-scale regional occurrence of submarine landslides.

As part of the STRA T AFROM project, the Hudson Apron area was selected for a detailed slope stability analysis. Results indicate that high pore pressure is necessary to trigger a failure. Under normal conditions, an excess pore pressure of more than 90% would be required for failure. On the other end, the actual strength profile would indicate a remaining marginal stability. Aggravating factors were the high sedimentation rate cyclicity and resulting layering inducing high excess pore pressures, and potentially gas pressures and earthquakes.