ALBERT

Description: Bathymetric data was recorded during the R/V 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 plume and/or 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 Master 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 environments (slope, abyssal plain, Walvis-Ridge) by two KONGSBERG multibeam echosounders (MBES) EM120 and EM1002 and the sub-bottom profiler PARASOUND. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval. Description of the data source: During the MSM20/1 cruise, the KONGSBERG EM1002 multibeam ecosounder (MBES) was utilized to perform bathymetric mapping in water depths of maximum 1000 m. A semi-circular transducer array with a radius of 45 cm and an angular extent of 160° transmits and receives acoustic signals at a standard frequency of 95 kHz. The systems uses different pulse lengths of 0.2 ms, 0.7 ms and 2 ms to maximize coverage in deeper waters. If the angular exceeds 100°, the transducer array will operate in three sectors with specific frequencies. With 111 beams and a beam width of 2° by 2°, the EM1002 provides the possibility of high range sampling with a maximum ping rate above 10 Hz. For further information on the system, consult https://www.km.kongsberg.com/. The position and depth of the water column is estimated for each sounding through the two-way-travel time, beam angle and ray bending due to refraction in the water column by sound speed variations. During the MSM20/1 cruise, eight sound velocity profiles (SVP) were taken, of which two were applied to the EM1002 data. EM1002 hydroacoustic data was acquired simultaneously with EM120 and Parasound sub-bottom profiles. Due to a crash of the EM120, detailed surveying was carried out with the EM1002 in the shallow waters of the continental shelf. Responsible person during this cruise / PI: Wilhelm Weinrebe (wweinrebe@ifm-geomar.de), Tilmann Schwenk (tschwenk@marum.de) & Paul Wintersteller (pwintersteller@marum.de) Chief Scientist: Wolfram Geissler (Wolfram.Geissler@awi.de) CR: https://www.tib.eu/en/search/id/awi%3Adoi~10.2312%252Fcr_msm20_1/ CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2012/20120062.htm 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