The paper sketches some leading ideas in phenomenology of perception and structural geography in the sense of Gilles Ritchot and Gaëtan Desmarais. Considering the key approach of discontinuities in the theory of urban form, it next scrutinizes the basic problem of the segmentation and the emergence of qualitative discontinuities in substrata spaces. Moreover, it points out the way in which the morphological processing of images makes understandable the mechanisms individuating localized spatial domains. Those mechanisms can be adequately modeled with the help of morphodynamical formalisms, especially variational models of spatial segmentation (Mumford and Shah, 1989) as well as multi-scale models driven by non linear anisotropic diffusion equations (Malik and Perona, Morel). Some examples of geographic images are analyzed.