The simple tectonic history of the South Sandwich island arc, a classic intra-oceanic arc lying in the South Atlantic Ocean, provided excellent opportunities for the Sandwich Lithospheric and Crustal Experiment (SLICE), conducted early in 1997, to investigate how, and at what rates, the Earth's crust is modified by subduction processes. The SLICE investigations of the South Sandwich island arc and the East Scotia Sea back-arc basin (Figure 1) included onshore and offshore recording of controlled-source and earthquake seismic data, establishment of geodetic GPS monuments on two islands, a new geological survey of the islands, and sampling of the islands and sea floor. Knowledge of the structure, geodynamics, and composition of this arc system is important because its simple tectonic history will allow estimation of the rates at which subduction processes modify the crust, and