Evolution of the yardangs at Rogers Lake, California
Yardangs are streamlined, wind-eroded hills common to most deserts. Yardangs at Rogers Lake, Mojave Desert, California, have streamlined forms characteristic of objects eroded by moving fluids, a teardrop shape that approaches an ideal 1:4 width-to-length ratio. In wind-tunnel simulations, miniature forms of various shapes changed sequentially by (1) erosion of the windward corners, (2) erosion of the windward slope, (3) erosion of the leeward corners and flanks, and (4) erosion of the leeward slope. Prominent mechanisms in yardang evolution apparently are abrasion at the windward end and deflation and reverse air flow near the middle and at the downstream end. Width-to-length ratios of yardangs are grossly similar to those of some fluvial and glacial streamlined landforms. The low kinetic energy of wind relative to ice and water, the erosional resistance to wind of most rocks, the rarity of long-term, unidirectional winds, and the presence of running water, topographic roughness, and vegetation all limit the abundance of yardangs.