Mæander
For alternative betydninger, se Mæander (flertydig). (Se også artikler, som begynder med Mæander)
For alternative betydninger, se 
En mæander, meander, mæandersving, mæanderslyngning eller mæanderbue er et vandløbs slyngning.[1] Ordet mæander er afledt fra Maíandros, som er det græske navn på floden, der på dansk hedder den store Mæander og på tyrkisk Büyük Menderes.[2] Fænomenet kendes fra talrige luftfotos af Amazonas, hvor man også ser de karakteristiske afsnøringer med isolerede sving på det tidligere flodløb.
Mæandere dannes, når flodens strømning eroderer flodbredden i ydersiden af et sving, og materialet aflejres langs indersiden. Buerne bliver efterhånden så ekstreme, at buen bliver afskåret fra resten af floden og der opstår en hesteskosø, der med tiden tørrer ud.
Ornamenter som muligvis er afledt af mæander
Det er muligvis fra dette naturfænomenet mæander, at man har dannet et ornamentmønster, også kaldet mæander, hvor de buede slyng er erstattet af retvinklede knæk på lige linjer. Mønstret ses på masser af keramik fra den græsk-romerske oldtid. Ofte kaldes mønstret derfor også à la grecque-bort eller mæanderbort.
Hvis man sammenligner med de keltiske spiralslyng-ornamenter, kan der dog anes en anden baggrund for mæanderborten. I så fald skal betegnelsen nok tolkes som et senere tilføjet navn for et mønster, der fandtes i forvejen, eller at floderne i oldtiden havde navn efter et mønster som alle kendte.
Mæander vandløbsgalleri
Et dramatisk eksempel på erosionen ved mæandere, Horseshoe Bend
Nowitna-floden i Alaska
En mæanderbue brugt aktivt ved Besançon
Río Negro i Argentina er en af de mest mæanderfyldte floder i verden.
Kilder/referencer
- ^ ordnet.dk: mæander Citat: "...betydninger slyngning eller stærkt slynget forløb af et vandløb..."
- ^ ordnet.dk: Mæander (stort M) Citat: "...fra gr., efter den stærkt bugtede lilleasiatiske flod Maíandros..."
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Medier brugt på denne side
Forfatter/Opretter: Nils Jepsen /user:Nico, Licens: CC BY-SA 4.0
meandersving ved Vejle Å nordøst for Vingsted
Forfatter/Opretter: No machine-readable author provided. Mbz1 assumed (based on copyright claims)., Licens: CC-BY-SA-3.0
Horseshoe Bend of Page, Arizona,
The picture was taken byBrocken Inaglory
The Rio Negro is recognizable by astronaut crews from orbit as one of the most meandering rivers in South America. In this astronaut photograph, the entire floodplain (mostly ~10 kilometers wide) is covered with curved relicts of channels known as meander scars. Meander scars show the past positions of river bends. The Rio Negro is a dramatic example of how mobile a river can be; these meanders were produced as the river snaked across the plain in the very recent geological past, probably during the last few hundred years.
The main channel of the river, flowing south at this point—sixty kilometers south of the city of Choele Choel (not shown)—appears in partial sun glint at image right. Sun glint occurs when light is reflected off a water surface directly back towards the viewer, like a mirror, imparting a silvery sheen to those areas. When meander scars contain water they are known as oxbow lakes, some of which are also highlighted by sun glint in the image.
The orange tint to the water in one of the oxbow lakes (image center) could result from orange salt-loving algae. Their appearance here would be unusual since floodplain lakes are usually too fresh for algae blooms. But an explanation may lie in the location of the Rio Negro on the margin of Argentina’s arid Patagonian region, where annual rainfall is less than 300 millimeters (12 inches). Evaporation in this cloudless region could be high enough for some lakes to become salty.
The Rio Negro flows generally southeast from the Andes Mountains to the Atlantic Ocean. Its floodplain supports the biggest pear- and apple-growing region of Argentina. Rectangular farm boundaries can be seen at bottom center in the image. The river also hosts the world’s longest kayak regatta, which lasts six days. During the 1800s, the river was also the demarcation line between farmlands of European settlers and territory controlled by indigenous people.
Astronaut photograph ISS022-E-19513 was acquired on January 4, 2010, with a Nikon D2Xs digital camera fitted with an 800 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 22 crew.
Forfatter/Opretter: User:Maksim, Licens: CC BY-SA 3.0
Development of a bend in a river and the creation of an oxbow lake.
