ASA. Spain Yardangs in the Gobi Desert, aerial photograph. These yardangs are near Yumenguan, China. The Moon is seen in the sky at upper right. Yardangs are ridges of rock created by wind erosion. They form in dry areas where strong prevailing winds blow in a single direction, carrying abrasive particles that erode the rock to form the ridge shapes. In this case, sand is the abrasive material doing the eroding.