How do playas form in bolson-type deserts?

In a bolson—a flat-floored desert valley or depression entirely surrounded by mountains—a playa forms in the central basin where interior drainage collects. These basins require a setting where evaporation significantly exceeds water inflow.12

The formation process involves several key factors:

• Inundation and Sedimentation: During periods of runoff, the basin floor is periodically covered by water, creating a temporary lake. As this water slowly evaporates or infiltrates the groundwater system, it leaves behind deposits of fine-grained sediment, sand, and salts.2
• Maintenance of Flatness: The process of repeated flooding and subsequent evaporation is responsible for developing and maintaining the near-perfect flatness characteristic of these landforms.2
• Geologic Origins: While the basin itself may be formed by tectonic activity such as faulting or warping, the playa surface evolves through the accumulation of these lacustrine sediments or, in some cases, through the desiccation of a former lake.3
• Surface Evolution: Once formed, the surface is shaped by drying and shrinking, which can create polygonal salt wedges or desiccation cracks. Wind action further modifies the surface by deflating dried salts and clays, often depositing them downwind.45