This field of yardangs formed in poorly lithified sediments of a former lake bed in Egypt's Western Desert. Steady winds blew away the dust and silt, and in the process the windblown particles carved these remnants into the classic form called "mud lions." It is an easy speculation that these silent, evocative shapes inspired the ancient motif of the sphinx.
The higher "head" end of these yardangs faces into the wind. The front faces are undercut because wind-driven sand stays near the ground, and erosion is concentrated there. Yardangs may reach 6 meters in height, and in some places they have rugged tops held up by smooth, narrow necks sculpted by thousands of sandstorms. They may also be low ridges of rock without picturesque protuberances. An equally important part of a yardang is the pair of windblown excavations, or yardang troughs, on either side of it.
Geologists differ on the exact details of yardang formation, and that is no surprise given the difficulty of making long-term observations in the remote desert during sandstorms.
