‘Mud cracks’, as they are commonly called, form when muddy sediment is exposed to the air and dries out. This causes the mud to dehydrate, shrink and crack. Some Bible critics claim that mud cracks disprove the global flood, because they are supposedly found throughout the geological record, and therefore imply a series of prolonged periods of drying out, instead of one great watery cataclysm that laid down most sedimentary layers.
However, this argument is far from ‘rock solid’, because true mud cracks are easy to confuse with cracks formed by other mechanisms that don’t involve a period of drying out. For instance, it is well known that structures resembling mud cracks can form underwater. Moreover, research suggests that true mud cracks could develop within hours. So flood sediments, briefly exposed with tidal movements as the waters rose, could shrink and crack very quickly.
Thus cracks in mud don’t disprove the flood!