Coalescing fans are called bajadas. Playas or playa lakes form in the low-lying regions between mountain ranges. They are composed of fine sands, silts, and evaporites. In the early stages of evolution, alluvial fans and playas develop in the valleys between the mountains. In the later stages the sediment in the valleys thickens, mountain elevations are reduced, the mountain fronts retreat, and the alluvial fans coalesce to form bajadas.
Wind is an important agent for transporting sediment in deserts.
Moving air is like moving water in the ways in which it can transport sediment. Lowers the land surface. Deflation ends when desert pavement is established. Like streams and glaciers, wind erodes by abrasion. Windblown sand cuts and polishes.