Sand sea

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. The term takes its name from the Arabic word ʿarq (عرق), meaning "dune field". 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 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 (3.5×10^⁶ sq mi) and contains several ergs, such as the Chech Erg (24°34′N 2°35′W / 24.57°N 2.59°W / 24.57; -2.59) and the Issaouane Erg (31°11′N 7°56′E / 31.18°N 7.93°E / 31.18; 7.93) in Algeria. Approximately 85% of all the Earth's mobile sand is found in ergs that are greater than 32,000 km² (12,355 sq mi). Ergs are also found on other celestial bodies, such as Venus, Mars, and Saturn's moon Titan.

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