Land bridge

Land bridges hypotheses were in the 19th and early 20th century, a much used method in the context of the paleogeography.

Thus, an attempt was made at that time already been incurred disjoint, their different geographic distribution of closely related plant and animal species by former land connections to explain the fallen dry in the meantime or had risen above sea level. The lifting and lowering of individual crustal areas was then considered significantly more likely than a horizontal shift against each other or, in the case of a ceiling education, one above the other.

Even global land bridge hypotheses were widespread in the 19th and early 20th centuries. They have been postulated on a large scale and gave rise to a veritable wave of speculation over Sunken Continents with once thriving civilizations. It also inspired popular scientific works as well as esoteric, popular culture and literature. With the recognition of plate tectonics and the increasingly precise geological age determination they lost their importance.

Requirements

Until the 20th century in the Geotektonik and global geodynamics of the so-called Fixismus was widespread. Accordingly, the continents of the earth were horizontal motionless, structure-forming processes of the lithosphere found mainly vertically, by raising and lowering instead. As a key driver of such processes of Earth's development and orogenesis was the cooling or shrinkage Theory of the Earth. Measurements of the gravitational equilibrium and the appropriate lifting effects were possible in the 18th century. Charles Lyell, she pointed, among other things on the Scandinavian shield, and went assume that such effects worldwide and throughout the Earth's history played a role. The time allocation within the geological time scale was only relatively possible before the discovery of absolute age determination methods in geology and archeology, the duration of the era immediately before the present was far clearly overestimated in the 20th century.

The biogeography, the contrast was still in its infancy, the idea of raising and lowering of large land masses became widely uncritical. Matthias Glaubrecht According to the rather skeptical Darwin had dismissed the arbitrariness of some land bridge hypotheses with the remark that they were as easy to construct as a cooking grill pancakes. The biogeography long tried to make a static division into biotic districts and sub-regions. The early scientific work gave the land bridges also play a role in the bio - how ethnographic distribution.

Biogeographic studies

Major biogeographic research on the subject came from Alfred Russel Wallace and Philip Sclater Lutley, the so-called Wallace Line as biogeographical division between Asian fauna ( orientalis) and Australian fauna ( Australis ). A challenge was the different mobility of different species. Alfred Russel Wallace himself gave the distribution of the species by spreading on land, even over long distances and through shipment to a flotsam important role.

Emmett Reid Dunn and George Gaylord Simpson started in the mid of the 20th century more strongly related with statistical analysis to particular species. Simpson spoke of filter bridges or corridors that only certain types were available.

Wegener's Plattentektonikhypothese

Plate tectonics had already been supported by the first publications of Alfred Wegener after 1915 by several Biogeographen. However, in the beginning especially for phenomena of the Pleistocene and the Quaternary, ie the recent geological past, which is similar to Wegener's proposed mechanism and it turned out to be untenable due to the fact significantly slower timing of shifts.

The idea of land bridges, however, was so powerful in that the theses Wegener's been a long time not recognized. 1939, the annual meeting of the German Geological Association had been asked yet under the motto " The Atlantis question ."; Hans Cloos had thus addressed the problem of whether continental crustal fields were sunk in the Atlantic Ocean or Wegener's drift hypothesis zutreffe A majority were then still for the land bridge and against Wegener's hypothesis. Moreover, could be worked out later main arguments for Wegener and against the land bridges from an overview of biogeographic findings. currently Wegener's because of research controversies and coordination problems a corresponding synopsis was not present. Ernst Mayr According to the resistance of many Biogeographen against Wegener was initially justified and substantiated. then in the 1960s there was a renewal of plate tectonics, which provided useful results in particular for Cretaceous and Jurassic, but sets up still questions.

Regional land bridges

At times, an intermediate, Lusitanian land bridge was for different animal species that are both widespread in northern Portugal and the South of Ireland, suspected. Later, the distribution presented in this case, but out as a result of the earliest human colonization.

The Doggerland between England and Germany has already been identified by Clement Reid end of the 19th century as one term, probably glacial land bridge between Britain and the continent. 1931, there was intense interest because of Mesolithic finds. Recent research, among other things, since by Bryony Coles 1998 see it as a standalone mesolitisches settlement area of national importance, no more than pure land bridge. Other land bridges and significantly enhanced coastal areas were among other suspects in the environment of Wales and in the Irish Sea and partially identified. Presumably, the culture was hit on the Doggerland 6200 BC by a tsunami triggered by the Storeggaabrutschung and interrupted at the latest with the expiration of the Lake Agassiz into the Atlantic Ocean, the land bridge.

Global land bridges

On a continental scale in 1828 Adolphe Brongniart related Glossopterisfarne fell in India and Australia. 1859 these were also found in South Africa and 1895 as well as in South America. Therefore, we began to take for this Glossopteris flora a southern Gondwana supercontinent. The various investigations, by Joseph Dalton Hooker to southern beech or Ludwig Rutimeyer to recent faunas and various fossils in South America, South Africa and Australia, solidified this assumption.

End of the 19th century these ideas were increasingly popularized. By Philip Sclater Lutley the lemurs was closed to a former continent of Lemuria from today's distribution, Madagascar and India should have connected. Evolutionary biologist Ernst Haeckel speculated in his popular History of Creation (1868 ) about such a sunken land bridge between Madagascar and India as geographical origin of man. A similarly closed and popular scientific form can be found in Eduard Suess ' face of the earth from 1883 Haeckel used Lemuria also for the interpretation of many missing links of evolution history -. They were gone down with this land bridge.

Hermann von Jhering took in 1890 a land bridge called Archhelenis between South Africa and South America and expanded this idea in his popular history of the Pacific Ocean in 1927 to a compound called Archatlantis between North Africa and Florida and the West Indies, including the Azores, Canary Islands and Cape Verde. Theodor Arldt put 1922 a manual of paleogeography ago, in which he summarized various land bridges. 1939 was the thesis among other things in the Atlas de paléobiogéographie of Léonce Joleaud. The scientific land bridge hypothesis gave rise to another, ideologically justified speculation, in which the remains of once high-ranking civilizations were suspected on such land bridges. In addition to the Atlantis myth Lemuria as well as the location in the Pacific continent Mu addressed accordingly and ran off with some considerable effort.

Examples

  • Beringia, a glacial connection between Asia and North America
  • Doggerland between mainland Europe and the British Isles
  • Adam's Bridge (or Rama Setu ) between India and Sri Lanka
  • Archatlantis of the West Indies to North Africa
  • Archhelenis Brazil to South Africa
  • Archiboreis in the North Atlantic
  • Archigalenis of Central America, Hawaii to Asia
  • Archinotis from South America to Antarctica
  • Lemuria in the Indian Ocean,
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