Physical modelling of soil deformation over a moving basement shows that localisation of deformation is an important feature of response. Different patterns of response are observed in model tests on clay and sand. Internal localisations which do not extend to the boundaries of the soil mass are observed in the sand tests. Numerical modelling of this problem, with finite elements, has used the tij models with parameters chosen to represent typical clays and dense sands. The nature of the analyses is such that localisation can be inferred but not observed. Although results are presented in terms of contours of proximity to failure and contours of shear strain, it is study of stress paths followed by individual soil elements that is most instructive in indicating likelihood of localisation and in revealing the differences in clay sand response that result from their significantly different volume change characteristics.