Land bridge

Land bridge

A land bridge, in biogeography, is an "isthmus" or other land connection between otherwise separate areas, which allows animals and plants to cross and colonise new lands. Land bridges are commonly created by regression, in which sea levels fall, exposing previously submerged sections of continental shelf. 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. By 10,000 years ago, the sea level had risen to only 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.

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).

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.

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. Many land bridges were hypothesized, criss-crossing large areas of ocean, the most prominent of them being Lemuria. 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. 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.

ee also

*Habitat fragmentation
*Sea level rise


Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • land bridge — land′ bridge or land′bridge n. gel an actual or hypothetical strip of land that connects adjacent continental landmasses and serves as a route of dispersal for plants and animals • Etymology: 1895–1900 …   From formal English to slang

  • land bridge — noun : a strip of land connecting two landmasses (as two continents or a continent and an island) * * * 1. Geol. an actual or hypothetical strip of land, subject to submergence, that connects adjacent continental landmasses and serves as a route… …   Useful english dictionary

  • land bridge — 1. Geol. an actual or hypothetical strip of land, subject to submergence, that connects adjacent continental landmasses and serves as a route of dispersal for plants and animals: a prehistoric land bridge between Asia and North America. 2. a… …   Universalium

  • Land bridge (disambiguation) — A land bridge, in biogeography, is an isthmus or other land connection between what at other times are separate land masses which allows animals and plants to cross.Other uses:*Air rightsThe term land bridge sometimes refers to covering… …   Wikipedia

  • land bridge — /ˈlænd brɪdʒ/ (say land brij) noun 1. a narrow stretch of land linking two separate larger areas of land, as an isthmus. 2. (in biogeography) such a stretch of land, existing for a period in the past and significant in the distribution of living… …  

  • land bridge — noun a) in biogeography: an isthmus or other land connection between what at other times are separate land masses b) Travel by ferry from one country, via another country by road, then by another ferry crossing to a third country. An example is… …   Wiktionary

  • land bridge — noun an area of land formerly connecting two land masses which are now separate …   English new terms dictionary

  • Eurasian Land Bridge — Railway bridge on the Trans Siberian across the Kama River near Perm. The Eurasian Land Bridge, sometimes called the New Silk Road, is a term used to describe the rail transport route for moving freight and passengers overland from Pacific… …   Wikipedia

  • New Eurasian Land Bridge — Terminus of the Lanxin railway at Alataw Pass, where the Chinese rail system connects with that of Kazakhstan at Dostyk. From Kazakhstan, rail links extend into Russia. The New Eurasian Land Bridge, also called the Second or New Eurasian… …   Wikipedia

  • Bering Land Bridge National Preserve — Infobox protected area | name = Bering Land Bridge National Preserve iucn category = V caption = locator x = 18 locator y = 147 location = Seward Peninsula, Alaska, USA nearest city = Kotzebue, Alaska lat degrees = lat minutes = lat seconds = lat …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”