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The Isthmus of Panama is a land bridge whose appearance 3 million years ago allowed the Great American Interchange.

A land bridge, in biogeography, is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonise new lands. A land bridge can be created by marine regression, in which sea levels fall, exposing shallow, previously submerged sections of continental shelf; or when new land is created by plate tectonics; or occasionally when the sea floor rises due to post-glacial rebound after an ice age.

Prominent examples

• 
  Adam's Bridge (known as Rama Setu), connecting India and Sri Lanka
  


• The Bering land bridge, which intermittently connected Asia with North America as sea levels rose and fell under the effect of ice ages


• 
  Doggerland, a former landmass in the southern North Sea which connected the island of Great Britain to mainland Europe during the last ice age


• The Isthmus of Panama, whose appearance three million years ago allowed the Great American Interchange
  


• The Sinai Peninsula, linking Africa and Eurasia
  

Land bridge theory

In the 19th century a number of scientists noted puzzling geological and zoological similarities between widely separated areas. To solve these problems, "whenever geologists and paleontologists were at a loss to explain the obvious transoceanic similarities of life that they deduced from the fossil records, they sharpened their pencils and sketched land bridges between appropriate continents."^[1] The concept was first proposed by Jules Marcou in Lettres sur les roches du Jura et leur distribution géographique dans les deux hémisphères ("Letters on the rocks of the Jura [Mountains] and their geographic distribution in the two hemispheres"), 1857–1860.^[2]

The hypothetical land bridges included:^[1]

• 
  Archatlantis from the West Indies to North Africa


• 
  Archhelenis from Brazil to South Africa


• 
  Archiboreis in the North Atlantic


• 
  Archigalenis from Central America through Hawaii to Northeast Asia


• 
  Archinotis from South America to Antarctica


• 
  Lemuria in the Indian Ocean


• 
  Marsupials between South America and Australia.

The concept became obsolete with the gradual acceptance of continental drift and the development of plate tectonics by the mid-20th century.

See also

• Habitat fragmentation


• Sea level rise

References

External links

Look up land bridge in Wiktionary, the free dictionary.

• 
   Ernest Ingersoll (1920). "Land-Bridges Across the Oceans" . Encyclopedia Americana.