We investigate the geometry of two-dimensional polygonal cracking that forms on the air-exposed surface of dried starch slurries. Two different kinds of starches, made from potato and corn, exhibited distinguished crack evolution, and there were contrasting effects of slurry thickness on the probability distribution of the polygonal cell area. The experimental findings are believed to result from the difference in the shape and size of starch grains, which strongly influence the capillary transport of water and tensile stress field that drives the polygonal cracking.

We investigate the desiccation crack patterns on the surface of a drying paste made of calcium carbonate (CaCO 3 ) powder and distilled water. Forced vibration of the CaCO 3 paste prior to drying results in an anisotropic crack pattern, in which many long cracks develop along a specific preferred direction. We reveal that the preferred direction changes from perpendicular to parallel to the vibration direction at the threshold velocity of vibration. The transition is attributed to the reorientation of constituent particles subjected to the forced oscillatory flow of fluid in the paste.

 A drone was used to obtain aerial images of polygon patterns on columnar joints' outcrop surfaces at four different sites in Japan. Unexpected correlations between geometrical characteristics of the cross-section of prisms were revealed by image processing. Conclusions obtained from field measurements were consistent with those of analog experiments based on starch slurry.

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