Erg (landform)

[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 concentrated in two broad belts between 20° to 40°N and 20° to 40°S latitudes, which include regions crossed by the dry, subsiding air of the trade winds.

In South America, ergs are limited by the Andes Mountains, but they do contain extremely large dunes in coastal Peru and northwestern Argentina.

Almost all major ergs are located downwind from river beds in areas that are too dry to support extensive vegetative cover and are thus subject to long-continued wind erosion.

At least one million years is required to build ergs with very large dunes, such as those on the Arabian Peninsula, in North Africa, and in central Asia.

[8] Sand seas that have accumulated in subsiding structural and topographic basins, such as the Murzuk Sand Sea of Libya, may attain great thicknesses (more than 1000 m[9]) but others, such as the ergs of linear dunes in the Simpson Desert and Great Sandy Desert of Australia, may be no thicker than the individual dunes superposed on the alluvial plain.

[15] Ergs on Mars can exhibit strange shapes and patterns, due to complex interaction with the underlying surface and wind direction.

Approximately 15-20% of the surface is covered by ergs with an estimated total area of 12–18 million km2 making it the largest dune field coverage in the Solar System identified to date.

[17] The sand dunes are believed to be formed by wind generated as a result of tidal forces from Saturn on Titan's atmosphere.