Marine Geophysics and Hydroacoustics

M155 Fogo

Summary M155 - May 26th to June 30th, 2019 Pointe-á-Pitre (Guadeloupe) to Mindelo (Cape Verde)

RV  Meteor-Cruise  M155  realized  two  proposals  with  different  objectives.  The  main  part  of  the cruise was assigned to the proposal ‘The tsunamigenic gravitational flank collapse of Fogo volcano, Cape Verde  Islands’. The cruise contributes to the assessment of poorly constrained and heavily debated  tsunamigenic  potential  of  large  volcanic  island  flank  collapses. The  recent  discovery  of tsunamigenic  deposits  in  the  Cape Verdes  shows  that  Fogo  collapsed  catastrophically  at  ~73  ka, resulting in a mega-tsunami. More  This provides a unique opportunity to reconstruct the generation and impact of a mega-tsunami, directly linked to a study of its trigger mechanism. Accordingly, offshore collapse deposits were investigated by means of (1) high-resolution mapping with multibeam and side-scan sonar to accurately determine the run-out distance, and the number of collapse events; (2) seismic  profiling  to  image  the  deposits’  thicknesses  and  internal  structure;  and  (3)  coring  to establish a stratigraphy of collapse events. This study will put us at a critical juncture where the latest developments in tsunami modelling can be integrated with physical evidence from both the offshore and onshore. A smaller part of the cruise was assigned to the proposal ‘Seismic pre-site survey for an IODP site on the Cape Verde Plateau’. The IODP full-proposal ‘Cenozoic climate, productivity, and sediment transport at the NW African continental margin’ (IODP proposal 933-full) addresses Neogene climate, sedimentation and ocean productivity along the continental margin of NW Africa. A central site is proposed on the Cape Verde Plateau close to ODP Site 659 but no modern high-resolution seismic data are available for this area. A seismic survey around Site 659 would have aimed in identifying a location where the Plio-Pleistocene is thinner and the Miocene is thicker than at Site 659. This would allow to APC-XCB deeper into the Miocene. This part of the proposal, however, could not be realized due to a failure of the ship’s compressor.