in a desert region, area of large accumulation of sand, generally in the bottom of a huge basin in which a former river piled up alluvium. Ergs are areas of actively shifting dunes, “fossilized” dunes, or extensive sand sheets. The sand is generally loose and is extremely difficult to cross. In the Sahara Desert between Beni Abbès in Algeria and Ghadāmis in Libya, the Great Western and Great Eastern ergs are the most difficult of all Saharan areas and are generally avoided by modern trans-Saharan routes. The Libyan Desert is another extensive area of unmitigated sandy waste.

unit of energy or work in the centimetre-gram-second system of physical units used in physics; to lift a pound weight one foot requires 1.356 × 10⁷ ergs. It equals the work done by a force of one dyne acting through a distance of one centimetre and is equal to 10^-7 joule, the standard unit of work or energy.