Please note that this is an author-produced PDF of an article accepted for publication following peer review. a Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site 2Highlights ► Sediment deformation and instability processes require integrated investigations ► Regional geology and environment control pre-conditioning factors ► There is paucity of high-quality geotechnical data and links with geophysics ► Challenges remain with triggers, pore pressure, landslide dynamics and weak layers ► Hazard and risk require event identification, recurrence frequency and magnitudes ACCEPTED MANUSCRIPT 5 to be addressed. A few examples of causative or preconditioning factors not addressed in this paper are permafrost and freeze-thaw cycles, large sediment input at deltas, large tidal fluctuations, static and cyclic liquefaction, or creep. Other types of instabilities, like rock falls, lie beyond the scope of this work. Offshore GeohazardsA geohazards is defined as a geological condition which represents -or has the potential to develop further into -a situation leading to damage or uncontrolled risk. Submarine landsliding is one of the most critical of offshore geohazards. Other examples include shallow sediment deformation phenomena (e.g., mud diapirism, gas chimneys, pockmarks, gas hydrates), but also shallow water flows, shallow gas accumulations, and seismicity ( Figure 1). Specific threats to society are the disappearance of valuable land near the shorelines, devastation of coastal areas by landslidegenerated tsunamis and the destruction of seafloor installations (e.g., communication cables, pipelines, templates). Assessing and mitigating offshore geohazards also implies estimating of risks, where probabilities associated with the different scenarios are difficult to quantify (Vanneste et al., 2011a). This becomes of primary importance as exploration and field development has developed rapidly in areas where geohazards may pose a risk since the 1990's, considering that both natural causes and human interferences may provide the ultimate trigger for instability.The results from large-scale national and international geosurvey efforts (e.g., MAREANO, Norway;MaGIC, Italy; ZEE project, Spain; UNCLOS, USA; NEREIDA, Canada) -in addition to the site surveying and reservoir imaging done by the offshore industry -to map the continental margins in ever increasing resolution, clearly indicate that recent mass movements with a variety of dimensions are common features on the seabed. More data were collected in the framework of dedicated slope stability investigation programmes, e.g., COSTA. In this paper, we discriminate between mass movements or slope instabilities on the one hand side and more local sediment deformation processes on the other side, as these phenomena may require different investigation methods due to A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 7 clays with extrem...