The Galicia margin has been at the forefront the development and testing of models on the break-up of magma-poor passive margins. However the current paradigm of continental break-up is still largely based on two dimensional observations. The data presented here from a high resolution 3D seismic reflection data reveal in unprecedented detail the complexity of continental break-up. Using the 3D geometry of the faults, analysing fault displacement at a number of different levels, and mapping syn-rift sediments it has been possible to offer a new model of break-up. This model combines elements of previous models but offers a new degree of clarity over the mechanism including fault linkage. Slip initiates at different points on the a weakened serpentinised mantle forming a slip surface that propagates up through a network of faults forming the S reflector, a detachment fault whilst also dissecting the crust, allowing further water ingress and weakening. Progressive slip and weakening rotates slip surfaces, eventually new sites of slip initiation form that propagate through the crust forming a new fault network and ceasing slip on the previous network. Continued weakening and slip eventually leads to break-up
