The lakes are generally among the linear dunes, but a few exist within the crescentic dunes. Trees planted at the edges of the farms to protect the area from the wind may account for what is imaged on Landsat. That they are aligned in the same direction may indicate structural control of the ground water. The slipfaces of these 1-km wavelength coalescing crescentic dunes are toward the northeast. Small interdunal sabkas are adjacent to some of the slipfaces in the upper right.
Many blowouts are on the gentle faces of the dunes.
By using archaeological, thermoluminescence, and radiocarbon dating methods, Wasson et al . They consider that the dunes started accumulating during the last glacial maximum under the influence of a weak monsoon circulation. As the Earth warmed after the glaciation, the monsoon was reestablished, leading to stabilization. They also suggest that the dunes were partially vegetated during their formative phases. An example of semifixed dunes northeast of the Plate scene appears in Figure E-21.3 .