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International Ocean Discovery Program (IODP) Expedition 398, Hellenic Arc Volcanic Field, recovered volcanic and nonvolcanic sediments and Messinian evaporites, as well as the nonvolcanic basement. The total recovery of about 3.3 km has the potential to significantly expand our understanding of the volcanic and tectonic history of the Christiana-Santorini-Kolumbo volcanic field and the climate history of the eastern Mediterranean. Here we report semiquantitative bulk elemental analyses of X-ray fluorescence core scans for Site U1591, drilled off Christiani Island, and Site U1599, drilled off Anafi Island, and compare these to records of natural gamma radiation that were measured aboard the R/V JOIDES Resolution. 

The understanding of island arc volcanism and associated hazards requires study of the processes that drive such volcanism and how the volcanoes interact with their marine surroundings. What are the links and feedbacks between crustal tectonics, volcanic activity, and magma genesis? What are the dynamics and impacts of submarine explosive volcanism and caldera-forming eruptions? How do calderas collapse during explosive eruptions and then recover to enter new magmatic cycles? What are the reactions of marine ecosystems to volcanic eruptions? The Christiana-Santorini-Kolumbo (CSK) volcanic field on the Hellenic volcanic arc is a unique system for addressing these questions. It consists of three large volcanic centers (Christiana, Santorini, and Kolumbo), and a line of small submarine cones, founded on thinned continental crust in a 100 km long rift zone that cuts across the island arc. The marine rift basins around the CSK field, as well as the Santorini caldera, contain volcano-sedimentary fills up to several hundreds of meters thick, providing rich archives of CSK volcanic products, tectonic evolution, magma genesis and paleoenvironments accessible only by deep drilling backed up by seismic interpretations. We will drill four primary sites in the rift's basins and two additional primary sites inside the Santorini caldera. The expedition science has five main objectives, each with a leading testable hypothesis, and two secondary objectives. Deep ocean drilling will enable us to identify, characterize, and interpret depositional packages visible on seismic images, chemically correlate primary volcaniclastic layers in the rift fills with their source volcanoes, fill in the many gaps in the onshore volcanic records, provide a tight chronostratigraphic framework for rift tectonic and sedimentary histories, and sample deep subsurface microbial life.