pigments + water + white glue = desiccation cracks
I applied the mixture by brush to some depressions were water would have accumulated after flooding or heavy rain falls and let it dry. The shrinking paste created cracks revealing the dark underlying layer. This resulted in a nice contrast to the red oxide colored surface. Some white pigments mixed with thinned lacquer were used for salt and mineral incrustations.
Please also note the foot print of Tyrannosaurus rex in the upper left corner.