Why do clay-rich playa muds shrink and crack as they dry?

Clay-rich playa muds shrink and crack as they dry due to the loss of water held within the sediment, a process that varies in intensity depending on the specific clay minerals present. Among these, smectite clays exhibit the most significant shrinkage during desiccation.1

The physical contraction of these muds is further influenced by the presence of salts. As the playa dries, the deposition and crystallization of these salts within the developing cracks create a network of salt wedges, which enhances the overall cracking effect. Under conditions of prolonged drought, this sediment contraction can become extreme, leading to the formation of giant desiccation polygons that can span up to 90 metres across, with individual cracks reaching depths of more than 15 metres.1