abstract: Polygonal tesselations – that is, tilings of the plane by convex polygons – are often used to describe geological pattern formation. In this talk I would like to present a stochastic model for the crack evolution of these structures, and to show that, in an appropriate limit of this model, the dynamics of averaged quantities follows a system of ODE. This is joint work with Gabor Domokos and Krisztina Regos.