In South America, the word médanos refers to continental dune

Dune

In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...

s whereas dunas refers to dunes of coastal origin. Médanos may be vegetated or unvegetated. For example, the médanos of La Pampa in Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 are mostly vegetated dunes with occasional blowouts

Blowout (geology)

Blowouts are sandy depressions in a sand dune ecosystem caused by the removal of sediments by wind.Blowouts occur in partially vegetated dunefields or sandhills. A blowout forms when a patch of protective vegetation is lost, allowing strong winds to "blow out" sand and form a depression...

. On the other hand, the dunes of Médanos de Coro National Park in Venezuela are mostly unvegetated. An early description of unvegetated médanos in Peru is provided by the Swiss naturalist and explorer Johann Jakob von Tschudi

Johann Jakob von Tschudi

Johann Jakob von Tschudi was a Swiss naturalist and explorer.Tschudi was born in Glarus, and studied natural sciences and medicine at the universities of Neuchâtel, Leiden and Paris. In 1838 he travelled to Peru, where he remained for five years exploring and collecting plants in the Andes...

(1847):

"The médanos are hillock-like elevations of sand, some having a firm, others a loose base. The former, which are always crescent-shaped, are from ten to twenty feet high, and have an acute crest. The inner side is perpendicular, and the outer or bow side forms an angle with a steep inclination downward. When driven by violent winds, the médanos pass rapidly over the plains. The smaller and lighter ones move quickly forwards before the larger ones; but the latter soon overtake and crush them, whilst they are themselves shivered by the collision. These medanos assume all sorts of extraordinary figures, and sometimes move along the plain in rows forming most intricate labyrinths, whereby what might otherwise be visible in the distance is withdrawn from the view of the traveller. A plain often appears to be covered with a row of médanos, and some days afterwards it is again restored to its level and uniform aspect. Persons who have the greatest experience of the coast are apt to mistake their way, when they encounter these sandhills."

External links

• http://www.venezuelatuya.com/occidente/medanos.htm
• http://www.losmedanos.com/
• The Bibliography of Aeolian Research