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.