Changes

==Origin==

==Origin==

French, from Old French, from Middle Dutch; akin to [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] ''dūn'' down  

French, from Old French, from Middle Dutch; akin to [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] ''dūn'' down  

*[http://en.wikipedia.org/wiki/18th_century 1790]

*[https://en.wikipedia.org/wiki/18th_century 1790]

The [[modern]] word "dune" came into [[English]] from French circa 1790. In [[ancient]] times, words cognate to "dune" probably had the meaning of a built-up hill or [[citadel]] fortification.

The [[modern]] word "dune" came into [[English]] from French circa 1790. In [[ancient]] times, words cognate to "dune" probably had the meaning of a built-up hill or [[citadel]] fortification.

==Definitions==

==Definitions==

*1:  a hill or ridge of sand piled up by the [[wind]]

*1:  a hill or ridge of sand piled up by the [[wind]]

==Description==

==Description==

In [http://en.wikipedia.org/wiki/Physical_geography physical geography], a '''dune''' is a hill of sand built either by [[wind]] or [[water]] [[flow]]. Dunes occur in different forms and sizes, formed by [[interaction]] with the flow of air or water. 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. The [[valley]] or trough between dunes is called a ''slack''. A "dune field" is an area covered by extensive sand dunes. Large dune fields are known as [http://en.wikipedia.org/wiki/Erg_(landform) ergs].

In [https://en.wikipedia.org/wiki/Physical_geography physical geography], a '''dune''' is a hill of sand built either by [[wind]] or [[water]] [[flow]]. Dunes occur in different forms and sizes, formed by [[interaction]] with the flow of air or water. 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. The [[valley]] or trough between dunes is called a ''slack''. A "dune field" is an area covered by extensive sand dunes. Large dune fields are known as [https://en.wikipedia.org/wiki/Erg_(landform) ergs].

Some coastal areas have one or more sets of dunes running [[parallel]] to the shoreline directly inland from the beach. In most cases the dunes are important in protecting the [[land]] against potential ravages by [[storm]] waves from the [[sea]]. Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated with ancient lake or sea beds.

Some coastal areas have one or more sets of dunes running [[parallel]] to the shoreline directly inland from the beach. In most cases the dunes are important in protecting the [[land]] against potential ravages by [[storm]] waves from the [[sea]]. Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated with ancient lake or sea beds.

Dunes also form under the [[action]] of water flow ([http://en.wikipedia.org/wiki/Fluvial fluvial] processes), and on sand or gravel beds of [[rivers]], estuaries and the [[sea]]-bed.[http://en.wikipedia.org/wiki/Dune]

Dunes also form under the [[action]] of water flow ([https://en.wikipedia.org/wiki/Fluvial fluvial] processes), and on sand or gravel beds of [[rivers]], estuaries and the [[sea]]-bed.[https://en.wikipedia.org/wiki/Dune]

[[Category: Earth Science]]

[[Category: Earth Science]]