Why is it important to crack - dry
during pond Preparations.

The drying of the pond bottom is the most practical cheap and effective method of eliminating undesirable species in the pond prior to the culture period. Drying oxidizes harmful chemical substances especially sulphides and facilitates mineralization of organic matter. The pond is dried until the soil cracks or when it is firm enough to hold one's weight without sinking more than 5 cm on walking over the surface.

Hope that answers your question.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.