Erg (landform) and western Asia, and Central Australia. In South America, ergs are limited by the Andes Mountains, but they do contain extremely large dunes in coastal Peru and northwestern Argentina. They are also found in several parts of the northeast coast of Brazil. The only active erg in North America is in the Gran Desierto de Altar () that extends from the Sonoran Desert in the northwestern Mexican state of Sonora to the Yuma Desert of Arizona and the Algodones Dunes of southeastern California. An erg that has been fixed by vegetation forms the Nebraska Sandhills (). Sand seas and dune
Grand Erg Oriental northern oasis on a Trans-Saharan trade route. South of Wargla on this road, lies Hassi Messaoud ["blessed well"], which is located within the "Grand Erg". Until recently Hassi Messaoud was a small Saharan village, but has grown substantially on account of the local discovery of oil in 1956. An oil refinery has since been built, and the city (current population estimated at 60,000) is now served by an international airport. A desert road going east from Hassi Messaoud continues through the "Grand Erg", passing by a well named "Bordj Sif Fatima" ["Fatima's River Tower" perhaps], on its way to the