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Land bridge
 
 
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A land bridge, in biogeography
Biogeography

Biogeography is the study of the distribution of biodiversity over space and time. It aims to reveal where organisms live, and at what abundance....
, is an isthmus
Isthmus

File:The Spit Bruny Island.jpg File:IsthmusOfPanama.pngAn isthmus is a narrow strip of land connecting two larger land areas. Of note, the Isthmus of Panama connects the continents of North America and South America , and the Isthmus of Suez in Egypt connects Africa and Asia ....
 or wider land connection between otherwise separate areas, which allows terrestrial
Terrestrial

Terrestrial refers to things having to do with the land or the Earth....
 animal
Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s and plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s to cross over and colonise new lands. Land bridges can be created by marine regression
Marine regression

Marine regression is a geology process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, Transgression , occurs when flooding from the sea covers previously exposed land....
, in which sea level
Sea level

Mean sea level is the average height of the sea, with reference to a suitable reference surface. Defining the reference level , however, involves complex measurement, and accurately determining MSL can prove difficult....
s fall, exposing shallow, previously submerged sections of continental shelf
Continental shelf

The continental shelf is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is undersea during Ice age such as the current epoch by relatively shallow seas and Bay....
; or when new land is created by plate tectonics
Plate tectonics

Plate tectonics describes the large scale motions of Earth's lithosphere. The theory encompasses the older concepts of continental drift, developed during the first decades of the 20th century by Alfred Wegener, and seafloor spreading, understood during the 1960s....
; or occasionally when the sea floor rises due to post-glacial rebound
Post-glacial rebound

Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostatic depression....
 after an ice age
Ice age

The general term "ice age" or, more precisely, "glacial age" denotes a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers....
.


he 19th century a number of scientists noted puzzling geological and zoological similarities between widely separated areas.






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A land bridge, in biogeography
Biogeography

Biogeography is the study of the distribution of biodiversity over space and time. It aims to reveal where organisms live, and at what abundance....
, is an isthmus
Isthmus

File:The Spit Bruny Island.jpg File:IsthmusOfPanama.pngAn isthmus is a narrow strip of land connecting two larger land areas. Of note, the Isthmus of Panama connects the continents of North America and South America , and the Isthmus of Suez in Egypt connects Africa and Asia ....
 or wider land connection between otherwise separate areas, which allows terrestrial
Terrestrial

Terrestrial refers to things having to do with the land or the Earth....
 animal
Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s and plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s to cross over and colonise new lands. Land bridges can be created by marine regression
Marine regression

Marine regression is a geology process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, Transgression , occurs when flooding from the sea covers previously exposed land....
, in which sea level
Sea level

Mean sea level is the average height of the sea, with reference to a suitable reference surface. Defining the reference level , however, involves complex measurement, and accurately determining MSL can prove difficult....
s fall, exposing shallow, previously submerged sections of continental shelf
Continental shelf

The continental shelf is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is undersea during Ice age such as the current epoch by relatively shallow seas and Bay....
; or when new land is created by plate tectonics
Plate tectonics

Plate tectonics describes the large scale motions of Earth's lithosphere. The theory encompasses the older concepts of continental drift, developed during the first decades of the 20th century by Alfred Wegener, and seafloor spreading, understood during the 1960s....
; or occasionally when the sea floor rises due to post-glacial rebound
Post-glacial rebound

Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostatic depression....
 after an ice age
Ice age

The general term "ice age" or, more precisely, "glacial age" denotes a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers....
.

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;
  • The Isthmus of Panama
    Isthmus of Panama

    The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North America and South America....
    , whose appearance 3 mya
    Mya (unit)

    In astronomy, geology, and paleontology, mya or "m.y.a." is an abbreviation for "million years ago". Like the related unit bya, mya is traditionally written in lower case....
     allowed the Great American Interchange
    Great American Interchange

    The Great American Interchange was an important zoogeography event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa, as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents....
    ;
  • The Sinai Peninsula
    Sinai Peninsula

    The Sinai Peninsula or Sinai is a triangular peninsula in Egypt. It lies between the Mediterranean Sea to the north and the Red Sea to the south, forming a land bridge between Africa and Southwest Asia....
    , linking Africa
    Africa

    Africa is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km? including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area....
     and Eurasia
    Eurasia

    Eurasia is a large landmass covering about 53,990,000 km? or about 10.6% of the Earth's surface . Often considered a single continent, Eurasia comprises the traditional continents of Europe and Asia, concepts which date back to classical antiquity and the borders for which are somewhat arbitrary....
    ;
  • Doggerland
    Doggerland

    Doggerland is a name given by geologists to the former landmass in the southern North Sea that connected the island of Great Britain to mainland Europe during the Wisconsin glaciation....
    , a former landmass in the southern North Sea
    North Sea

    The North Sea is a marginal sea, epeiric sea on the European continental shelf. The Dover Strait and the English Channel in the south and the Norwegian Sea in the north connect it to the Atlantic Ocean....
     which connected the island of Great Britain
    Great Britain

    Great Britain is an island lying to the northwest of Continental Europe. It is the List of islands by area, and the largest in Europe. With a population of 58.9 million people it is List of islands by population....
     to mainland Europe
    Europe

    Europe is, conventionally, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural , the Caspian Sea, and by the Caucasus Mountains to the southeast....
     during the last ice age.


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." The concept was first proposed by Jules Marcou
Jules Marcou

Jules Marcou was an eminent Switzerland-United States geologist.He was born at Salins-les-Bains, in the d?partement in France of Jura , in France....
 in Lettres sur les roches du Jura.

These hypothetical land bridges included:
  • Lemuria
    Lemuria (continent)

    Lemuria is the name of a hypothetical "Lost lands" variously located in the Indian Ocean and Pacific Ocean Oceans. The concept's 19th century origins lie in attempts to account for discontinuities in biogeography....
     in the Indian Ocean
  • Archiboreis in the North Atlantic
  • Archatlantis from the West Indies to North Africa


  • Archigalenis from Central America thru Hawaii to Northeast Asia
  • Archinotis from South America to Antarctica


All of these became obsolete with the discovery of continental drift
Continental drift

Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912....
 and the development of plate tectonics
Plate tectonics

Plate tectonics describes the large scale motions of Earth's lithosphere. The theory encompasses the older concepts of continental drift, developed during the first decades of the 20th century by Alfred Wegener, and seafloor spreading, understood during the 1960s....
 by the mid-20th century.

See also

  • Habitat fragmentation
    Habitat fragmentation

    Habitat fragmentation is a process of Natural environmental change important in evolution and conservation biology. As the name implies, it describes the emergence of discontinuities in an organism's preferred environment ....
  • Sea level rise