Almost all glazes contain clay (e.g. kaolin, ball clay, bentonite, native clays). Clay is employed to supply Al2O3 to the chemistry, to suspend the slurry and to harden the dry glaze. Clays shrink as they dry, thus glazes containing clay will also shrink. Some shrinkage can be tolerated, but if there is too much the glaze will form cracks. This can be serious enough to even appear like a dried up lake-bed. If ware to which this has happened is fired, the glaze will likely craw into islands as it melts.
Something is definitely wrong. What is it?
An example of how a glaze that contains too much plastic clay has been applied too thick. It shrinks and cracks during drying and is guaranteed to crawl. This is raw Alberta Slip. To solve this problem you need to tune a mix of raw and calcine material. Enough raw is needed to suspend the slurry and dry it to a hard surface, but enough calcine is needed to keep the shrinkage low enough that this cracking does not happen. The Alberta Slip website has a page about how to do the calcining.