Landbridges,>in biogeography, are described by Wikipedia as “an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize 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.”<
In the distant past, landbridges are believed to have played a critical part in early human migration. Similarly, landbridges, both real and speculative are important components in many Atlantis theories. There is no doubt that the ending of the last Ice Age and the consequent rising sea levels led to the creation of islands where continuous land has previously existed. The separation of Ireland and Britain from each other and from mainland Europe is just one example, the latter leading to a number of writers identifying ‘Doggerland‘, which lay between Britain and Denmark as the home of Atlantis.
The two most discussed landbridges were at the Bering Strait, where it is thought that it provided the gateway for humans to enter the Americas from Asia and an Atlantic landbridge, which was proposed as early as the 17th century and later by John B. Newman in 1849 [488.8], who wrote that “in former times an island of enormous dimensions, named Atlantis, stretched from the north-western coast of Africa across the Atlantic ocean and that over this continental tract both man and beast migrated westward.“
The Atlantic landbridge idea became quite popular by the end of the 19th and beginning of the 20th centuries and even as late as the 1970s when espoused by Rene Malaise(a), but is now completely abandoned.>Ignatius Donnelly referred to such a landbridge as a ‘connecting plateau’ linking Europe, Africa and America that allowed plants and animals to cross in both directions.<
Although there was only one suggestion that the Bering Strait was in any way connected with Plato’s Atlantis, several commentators identified an Atlantic landbridge as the ideal location for Plato’s Atlantis, particularly as he placed it in the Atlantic Sea. However, this should not be confused with the Atlantic Ocean, a word that had an entirely different meaning for the ancient Greeks.
The idea was initially put forward in order to explain the floral and faunal similarities shared by the Old World and the New World of the Americas. The hypothetical Atlantic landbridges or a series of steppingstone islands. also offered possible routes for the peopling of the Americas by Europeans and/or Africans. It was not long before the discovery of the Mid-Atlantic Ridge(b) seemed to confirm this idea. Then it was suggested that Atlantis existed on this landbridge, which was destroyed by rising sea levels after the last Ice Age, leaving just the Azores, Madeira and a few other islands as remnants.
A number of landbridges have been proposed for the Mediterranean and linked to a variety of Atlantis theories, the most notable being proposed for the straits of Gibraltar, Sicily, Messina and Bonifacio. Although it is evident that landbridges existed at most of these locations, to associate them with any particular Atlantis theory requires that the date of their existence is compatible with Plato’s narrative.
Less popular theories have been constructed involving landbridges in locations, such as the Caribbean and Indonesia.
(a) Atlantis, Vol.27, No.1, Jan-Feb 1974.
(b) From the Contracting Earth to early Supercontinents – Scientific American Blog Network