Abstract The NW African continental margin is well known for the occurrence of large-scale but infrequent submarine landslides. The aim of this paper is to synthesize the current knowledge on submarine mass wasting off NW Africa with a special focus on the distribution and timing of large landslides. The described area reaches from southern Senegal to the Agadir Canyon. The largest landslides from south to north are the Dakar Slide, the Mauritania Slide, the Cap Blanc Slide, the Sahara Slide and the Agadir Slide. Volumes of individual slides reach several hundreds of cubic kilometres; run-outs are up to 900 km. In addition, giant volcanic debris avalanches are widespread on the flanks of the Canary Islands. All headwall areas are complex with clear indications of multiple failures. The most prominent similarity between all investigated landsides is the existence of widespread glide planes that follow the stratigraphy, which points to weak layers as most important preconditioning factor for the failures. Landslides with volumes larger than 100 m 3 are close to being evenly distributed over time, contradicting previous suggestions that landslides off NW Africa occur at periods of low or rising sea level. The risk associated with the landslides off NW Africa, however, is relatively low due to their long recurrence rates.

Geoscientists play increasingly important roles in international development amidst population growth and concomitant demands on water resources and exposures to natural hazards. This paper demonstrates the value of geoscientists for public good by detailing the range and depth of contributions within a single case study of Dakar, Senegal. This urban agglomeration is home to 3 million residents and represents a major hub of business and migration within West Africa. Its unique geology and locus within the drought-prone western Sahel contribute to specific challenges that have strongly shaped its present cultural and environmental landscape. Sustainable development in Dakar depends in particular on groundwater monitoring, mapping of cliff retreat and landslides, flood studies, coastal erosion studies, and prediction of the local effect of sea-level rise. These critical geoscientific investigations, including fruitful collaborations between Senegalese and foreign geoscientists, are helping to mitigate the environmental effects of previous unplanned growth and to inform policy going forward.