  The present paper demonstrates how a natural crack mosaic resembling a random
tessellation evolves with repeated 'wetting followed by drying' cycles. The
natural system here is a crack network in a drying colloidal material, for
example, a layer of mud. A spring network model is used to simulate consecutive
wetting and drying cycles in mud layers until the crack mosaic matures. The
simulated results compare favourably with reported experimental findings. The
evolution of these crack mosaics has been mapped as a trajectory of a 4-vector
tuple in a geometry-topology domain. A phenomenological relation between energy
and crack geometry as functions of time cycles is proposed based on principles
of crack mechanics. We follow the crack pattern evolution to find that the
pattern veers towards a Voronoi mosaic in order to minimize the system energy.
Some examples of static crack mosaics in nature have also been explored to
verify if nature prefers Voronoi patterns. In this context, the authors define
new geometric measures of Voronoi-ness of crack mosaics to quantify how close a
tessellation is to a Voronoi tessellation, or even, to a Centroidal Voronoi
tessellation.
