Introduction to mud crack layer: Mud cracks are more common in coastal areas of lakes or oceans or in floodplain sedimentary environments. When unconsolidated sediments emerge from the water, they will be exposed to the sun and dry up, shrinking and cracking. The cracks formed at this time are mud cracks. The lobes of mud cracks are wide at the top and narrow at the bottom, roughly perpendicular to the layer, and are often filled with overlying sediment components.