Erg (landform) when liquid methane rained and eroded the ice bedrock, possibly in the form of flash floods. Alternatively, the sand could also have come from organic solids produced by photochemical reactions in Titan's atmosphere. 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. The term takes its name from the Arabic word "ʿarq" (), meaning "dune field". Strictly speaking, an erg is defined as a desert area that contains more than of aeolian or wind-blown sand
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