Cape Lopez is the point of Mandji island, Gabon, extending the furthest into the Atlantic Ocean. It consists of mainly-sandy delta deposits, underlain
by a very dense layer located at a depth of more than twenty metres.
The main ocean currents flow around the cape from West to East, carrying sediments eroded from the West coast towards the East coast. When they
enter Princes’ Bay, the currents are protected by the cape and slow down. Very fine sands, of very uniform grain size, are then deposited along the
East coast, resulting in its growth. Submarine landslides of varying magnitudes (up to several million cubic metres) occur frequently on the East
coast. The slides take place along very gentle slopes (less than 5°). A possible explanation of these recurrent landslides is that the relative densities of the local sands are lower than the critical densities. This makes them very sensitive to the generation of excess pore pressures, which may be refered to as “lateral spreading” phenomenon.
Under the action of growth or of any other load generating excess pore pressures, the sands lose their shear strength and flow.
