Sand sheets and dunes cover approximately 25 percent of the Sahara’s surface. The principal types of dunes include tied dunes, which form in the lee of hills or other obstacles; parabolic blowout dunes; crescent-shaped barchans and transverse dunes; longitudinal seifs; and the massive, complex forms associated with sand seas.

The Sahara desert has a variety of land features, but it is most famous for the sand dune fields that are often depicted in movies. The dunes can reach almost 600 feet (183 meters) high, and they cover about 25% of the entire desert, according to the Encyclopedia Britannica.

Most of the Sahara Desert is undeveloped and features a varied topography. Most of its landscape has been shaped over time by wind and includes sand dunes, sand seas called ergs, barren stone plateaus, gravel plains, dry valleys, and salt flats. Around 25% of the desert is sand dunes, some of which reach over 500 ft (152 m) in height.

The sandy areas of the Sahara are called ergs, and are covered with sand dunes and shifting sands. The Grand Erg Oriental is one of the largest areas of sand desert in the Sahara, spanning parts of Tunisia and Algeria.

The Sahara is mainly rocky hamada (stone plateaus); ergs (sand seas – large areas covered with sand dunes) form only a minor part, contrary to common misconception, but many of the sand dunes are over 180 metres (590 ft) high.