Erg

An erg is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover. The word is derived from the Arabic word ʿarq, meaning "dune field". Strictly speaking, an erg is defined as a desert area that contains more than 125 km² of aeolian or wind-blown sand and where sand covers more than 20% of the surface. Smaller areas are known as "dune fields". The largest hot desert in the world, the Sahara, covers 9 million square kilometres and contains several ergs, such as the Chech Erg and the Issaouane Erg in Algeria. Approximately 85% of all the Earth's mobile sand is found in ergs that are greater than 32,000 km². Ergs are also found on other celestial bodies, such as Venus, Mars, and Saturn's moon Titan. ()