Erg (landform)

An erg (also sand sea or dune sea, or sand sheet if it lacks dunes) is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover.^[1] The word is derived from the Arabic word ʿarq (عرق), meaning "dune field".^[2] Strictly speaking, an erg is defined as a desert area that contains more than 125 km² (48 sq mi) of aeolian or wind-blown sand^[3] and where sand covers more than 20% of the surface.^[2] Smaller areas are known as "dune fields".^[4] The largest hot desert in the world, the Sahara, covers 9 million square kilometres (3.5×10^⁶ sq mi) and contains several ergs, such as the Chech Erg and the Issaouane Erg in Algeria.^[5] Approximately 85% of all the Earth's mobile sand is found in ergs that are greater than 32,000 km² (12,355 sq mi),^[6] the largest being the Rub' al Khali, the Empty Quarter of the Arabian Peninsula. Ergs are also found on other celestial bodies, such as Venus, Mars, and Saturn's moon Titan.