Example of results of analogue modelling of shortening of a weak continental lithosphere with a free lateral boundary. (a) Surface view of a 50% shortened model showing lateral extrusion accommodated by transfer shear zones. Block rotations between shear zones are underlined by initially orthogonal coloured markers drawn on model surface before deformation. (b) Cross-sections far from the extruded zone (1) and within it (2). These underline significant differences between ductile crust thickness far (doubled ductile crust) and within the extruded zone. Modified after Cagnard et al., 2006a.