A land bridge, in biogeography, is an isthmus or other land connection between what at other times are separate areas which allows animals and plants to cross and colonise new lands. Biogeography is the study of the distribution of Biodiversity over Space and Time. An isthmus is a narrow strip of land connecting two larger land areas Plants are living Organisms belonging to the kingdom Plantae. Colonisation (also known as Colonization) occurs whenever any one or more species populates a new area Land bridges are commonly created by regression, in which sea levels fall exposing previously submerged sections of continental shelf. Marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level Mean sea level (MSL is the average (mean height of the Sea, with reference to a suitable reference surface The continental shelf is the extended perimeter of each Continent and associated Coastal plain, which is covered during interglacial periods such Land bridges are also formed by: (a) upthrust at the edge of continental plates; and (b) glacial retreat alleviating pressure on shallow marine formations (e. g. the emergence of Oland, Sweden)

The most recent significantly low sea levels were about 20,000 years ago (during the Upper Paleolithic) when worldwide sea levels were about 120 meters below today's level. is the second largest Swedish island and the smallest of the traditional Provinces of Sweden. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun The Upper Paleolithic (or Upper Palaeolithic) is the third and last subdivision of the Paleolithic or Old Stone Age as it is understood in Europe Africa The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International By 10,000 years ago, the sea level had risen to 20 meters below today's level. Sea level rise can occur as a result of global warming, or apparent sea level rise may occur as a result of glacial depression or certain tectonic movements. Sea-level rise is an increase in Sea level. Multiple complex factors may influence this change Global warming is the increase in the average measured temperature of the "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics.

Examples

Perhaps the best-known example is the Bering land bridge, which joined present-day Alaska and eastern Siberia at various times during the Pleistocene ice ages, enabling humans to migrate from Eurasia to the Americas (see models of migration to the New World). The Bering land bridge was a Land bridge roughly 1000 miles (1600 km north to south at its greatest extent which joined present-day Alaska and eastern Siberia Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving The Pleistocene ('plaɪstəsin is the epoch from 18 million to 10000 years BP covering the world's recent period An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus For the superstate in George Orwell 's novel see Nations of Nineteen Eighty-Four. The Americas are the lands of the Western hemisphere or New World, consisting of the Continents of North America and South America There are several popular models of migration to the New World proposed by the anthropological community

Another example is Doggerland, a former landmass in the southern North Sea which connected the island of Great Britain to mainland Europe during the last ice age. Doggerland is the former landmass in the southern North Sea which connected the island of Great Britain to mainland Europe during the last ice The North Sea is a marginal, Epeiric sea of the Atlantic Ocean on the European Continental shelf. See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets

Land bridge theory

Before the theory of plate tectonics, it was believed that land bridges could explain the occurrence of species in separate continents and the resemblances of geologic formations on different continents. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions Many land bridges were hypothesized, criss-crossing large areas of ocean, the most prominent of them being Lemuria. An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. Lemuria (lɨˈmjʊəriə is the name of a hypothetical " lost land " variously located in the Indian and Pacific Oceans However, when the sea bed of the Atlantic Ocean was mapped using echo sounding between 1924 and 1927, no remains of land bridges could be found. "Ocean Floor" redirects here For the 2001 song by Audio Adrenaline, see Lift (Audio Adrenaline album. Echo sounding is the technique of using Sound pulses directed from the surface or from a submarine vertically down to measure the distance to the bottom by means of sound waves Though this was a strong argument for Alfred Wegener's theory of continental drift, it would take about 50 more years until mainstream geology fully acknowledged the motion of continents. Alfred Lothar Wegener ( November 1, 1880 – November 2 or 3 1930 was a German Scientist and Meteorologist. Continental drift is the movement of the Earth 's Continents relative to each other Mainstream is generally the common current of Thought of the Majority. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit

See also

• Habitat fragmentation
• Sea level rise