Executive Summary
The NSF-MARGINS program began because of a community perception that continental margin science could benefit from increased communication, cooperation, and integration between scientists engaged in a wide variety of observations, experiments, and theoretical modeling in studies crossing the shoreline. With an emphasis on studying active processes, the objective of MARGINS is to develop a self-consistent understanding of the processes that are fundamental to margin formation and evolution, comprising lithospheric deformation, magmatism and mass fluxes, sedimentation, and fluid flow, together with their interactions and feedbacks. The MARGINS process has been to work with the community to identify major areas of important research that could benefit from this approach, leading to four major initiatives. These are: Rupturing of the Continental Lithosphere (RCL) and the birth of an ocean; Subduction Factory (SubFac), to understand the processes controlling the chemical cycle in subduction zones and the geodynamic information contained therein; SEIZE, the Seismogenic Zone Experiment to investigate the great earthquakes occurring along the plate boundary in subduction zones; and Source-to-Sink (S2S), which links geomorphology, erosion and transport by the sedimentary processes that form the stratigraphic record from nearly instantaneous to geologic timescales. Within each initiative, widely advertised and attended NSF-supported workshops helped to identify key scientific issues, developed criteria essential for successful studies, evaluated candidate geographical localities and sought consensus on optimal focus sites, and summarized the aspirations of the research community in the various Science Plans, which have been widely disseminated by NSF and the MARGINS Office. Implementation of these Science Plans is achieved by concentrating resources on focus sites targeted for intense, multidisciplinary programs of research in which an ongoing dialogue among field experiment, numerical simulation, and laboratory analysis researchers is fundamental and symbiotic, and is facilitated by a continuing series of science and planning workshops. The MARGINS program seeks a quantum leap in our quantitative knowledge and predictability of Earth system behavior in order to enhance Earth Science research for scientific advancement, but also for societal relevance, exploitation, exploration, and hazard mitigation. In the first half of its decadal existence, a fundamental objective of the MARGINS program has already been attained - the building of a large community of scientists who are well-informed across a broad range of disciplines and sub-disciplines not related to their own.
Following are thumbnail sketches of each initiative:

1) RCL - the initiation, evolution, and eventual destruction of continent- ocean margins involve the coupled interaction of mechanical, fluid, chemical, and biological processes. These processes result in the accumulation of most of the Earth’s valuable resources and the focusing of the principal geologic hazards at margins; the locus of the greatest population density. The Rupturing of Continental Lithosphere (and birth of an ocean) experiment will proceed by focused investigations of the four-dimensional style, distribution, and depth partitioning of extension within continental lithosphere to determine the spatial and temporal variations in the rheology of the lithosphere, why rifts form where they do, and the forces required to sever continental lithosphere.

2) SubFac - Subduction of oceanic plates causes earthquakes, tsunamis, and explosive volcanism, and also gives rise to ore deposits, geothermal energy, and the continental crust we live on. The Subduction Factory Initiative focuses research on two contrasting subduction zones to address fundamental questions about forcing functions for magmatism and fluid flow, volatile cycles through convergent margins, and mass balance and growth of the continents.

3) SEIZE - Subduction zones also generate the world’s largest and most destructive earthquakes and tsunamis, and host much of the world’s population The Seismogenic Zone Experiment studies the shallow subduction plate interface that is locked and accumulates elastic strain, periodically released in large or great earthquakes. Questions focus on the controls on the distribution of seismic energy release, on the heterogeneities in the locking behavior of the interface, on the rate of propagation and slip rates of earthquakes, and on the nature of temporal changes in strain, fluid pressure and stress during the seismic cycle.

4) S2S - The Source-to-Sink initiative will provide a comprehensive study of linked, terrestrial and marine sediment dispersal systems over the range of time scales for which sedimentary processes operate. Observational, laboratory and theoretical studies will be integrated to allow the modeling of entire, linked sedimentary systems as opposed to only their components. Questions center around the role of changing tectonics, climate and sea level as forcing functions in the production, transport and storage of sediments and solutes; processes initiating erosion and sediment transfer, and their interactions; and the interplay of sedimentary processes and forcing functions in creating the stratigraphic record.

With the maturing of the science plans and implementation proceeding in all initiatives, the MARGINS program can focus more attention on data management and education and outreach. Data policies for the archiving and timely release of MARGINS funded data are now in place and dedicated focus site database design, schema, and template experiments are underway. The MARGINS Office now has a half-time FTE to pursue Education and Outreach activities. Reflecting the strengths of the MARGINS Steering Committee and Office, efforts will focus on undergraduate and informal education. Early activities include the creation of a MARGINS post-doctoral fellowship scheme, a MARGINS Images library for undergraduate instructors, and collaboration with the St. Louis Science Center with the ultimate goal of developing MARGINS related exhibits. All products will be made available to the MARGINS science community for adaptation and use nationwide. Collectively, the formal MARGINS publications, the products of the Education and Outreach efforts, and the databases of the MARGINS focus sites represent an important legacy and resource for future researchers-NSF’s “investment in the future.”