Sediment echosounder data was recorded during RV MARIA S. MERIAN cruise MSM20/1 between 06.01.2012 and 15.01.2012 at the Walvis Ridge in the eastern South Atlantic. The aim of the cruise was to investigate critical geologic parameters for continental break-up and plume processes offshore northern Namibia, like crustal thickness and structure of the underlying Earth's mantle. Geophysical methods were utilized to visualize structures relating to fossil plumes and deformation processes. Several broadband ocean-bottom seismometers were recovered from the seafloor to gather seismological data. Hydroacoustic work during MSM20/1 was carried out as part of the “floating university” in order to teach masters students the acquisition, processing and interpretation of hydroacoustic data. The data was derived from different water depths (from upper slope down to the deep-sea basin) and various environments (slope, abyssal plain, Walvis Ridge) by two KONGSBERG multibeam echosounders (MBES) EM120 and EM1002 and the sub-bottom profiler ParaSound (https://doi.org/10.2312/cr_msm20_1). During the R/V MARIA S. MERIAN cruise MSM20/1, the hull-mounted parametric sub-bottom profiler ATLAS PARASOUND P70 was used to conduct information about the sediment sub-surface and water column. It is utilizing the parametric effect of the non-linear relation of pressure and density during sonar propagation. Data acquisition was performed using measured real-time values of surface sound velocity and a static sound velocity profile of 1500 m/s. Using the software ATLAS PARASTORE raw data was processed and converted to the *.sgy file format. During the cruise, ParaSound was permanently running in a 24/7 schedule. The system worked quite reliable without any significant problems, however, the high amount of so-called system recovery actions disturbed the acquisition of truly continuous profiles (https://doi.org/10.2312/cr_msm20_1).

Responsible person during this cruise / PI: Wilhelm Weinrebe (wweinrebe@ifm-geomar.de), Tilmann Schwenk (tschwenk@marum.de) & Paul Wintersteller (pwintersteller@marum.de)A special thanks goes to the participants of the Floating University during MSM20/1: Gesa Barkawitz, Johanna Bruckmann, Eva Eibl, Milen Iliev, Janina Kammann, Sofia Kufner, Irena Schulten, Daniela Wolf, Timo Zander, Andre Vollmert, Monika Tangeni Emvula, Justina Nafje-Ovanhu Hamalwa