Soda Lake. Playa lakes are among the most flat landforms in the world. In wet years, the playa contains standing water. In drier times, water may lie very near the surface of the playa. Capillary action draws the water upward where it evaporates, leaving a white, puffy crust of evaporite minerals such as sodium carbonate and sodium bicarbonate. ( source USGS) Mojave River, Mojave desert, San Bernardino County, California, USA. .© febr. 24 2007 Marco van Middelkoop/Aerophoto-Schiphol