SONNE SO255

North of New Zealand, the Vitiaz-Kermadec subduction system extends over two and a half thousand kilometers. Here, the Pacific Plate subducts under the Australian plate. There is increasing international interest in the initiation and evolution of this system. The Kermadec arc, which is presently located above the subduction zone, and the Havre Trough backarc basin were formed by splitting of the older Vitiaz arc into the Kermadec and Colville ridges. But how exactly did the subduction zone initiate and evolve? And what processes have led to the splitting of the older Vitiaz Arc and the formation of the backarc basin? In collaboration with scientists from New Zealand, Japan and the US, R/V SONNE cruise SO255 will conduct extensive bathymetric mapping, sub-bottom, magnetic and gravity profiling, and hard-rock sampling via dredging to investigate the physical and chemical conditions that control the development of subduction zones, including subduction initiation, evolution of mature arc systems, and the transition from arc splitting to backarc basin generation. This approach will also provide basic data for a better evaluation of the impact of subduction volcanism on the environment. The geological program of the cruise will be completed by minor biological investigations.