Land bridge
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
- 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
- The Adam's Bridge (known as Rama Setu), connecting India and Sri Lanka
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 these:[3]
- 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.
Most land bridges became obsolete with the gradual acceptance of continental drift and the development of plate tectonics by the mid-20th century.
See also
References
- ↑ William R. Corliss, Mysteries Beneath the Sea, Apollo Editions, June 1975, Chapter 5: "Up-and-Down Landbridges" ISBN 978-0815203735
- ↑ William R. Corliss, op. cit., "The basic idea is usually attributed to Jules Marcou…."
- ↑ All examples taken from Corliss, op. cit.
External links
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