The continent-ocean boundary (COB) or continent-ocean transition (COT) or continent-ocean transition zone (COTZ) is the boundary between continental crust and oceanic crust on a passive margin or the zone of transition between these two crustal types. The identification of continent-ocean boundaries is important in the definition of plate boundaries at the time of break-up when trying to reconstruct the geometry and position of ancient continents e.g. in the reconstruction of Pangaea.