Land Bridge


A physical land bridge, is an or other land connection between what at other times are separate land masses which allows animals and plants to cross and colonize 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 upthrust at the edge of continental plates.

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 20 meters below today's level.

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. Another land bridge may have connected Great Britain to Europe at around the same time.

A land bridge surviving to the present day is the Sinai, connecting North Africa with Southwest Asia. Hominids and humans probably migrated out of Africa through the Sinai.

A land bridge that rose from the sea floor because of upthrust at the edge of a continental plate is Central America. The Cocos Plate, an oceanic tectonic plate off the west coast of Central America, is being subducted in a convergent boundary under the North American Plate to the north and the South American Plate to the south. This caused first an island arc and then continuous land to emerge.

Before the theory of Plate Tectonics, it was believed that land bridges could explain the occurrence of species in separate continents. Many land bridges were thought up, cross-crossing large areas of ocean. They also apparently disappeared without a trace. Continental drift Read more




In the News ...



2011 Tsunami enabled hundreds of aquatic species to raft across Pacific   PhysOrg - September 28, 2017
The 2011 Japanese tsunami set the stage for something unprecedented. For the first time in recorded history, scientists have detected entire communities of coastal species crossing the ocean by floating on makeshift rafts. Nearly 300 species have appeared on the shores of Hawaii and the U.S. West Coast attached to tsunami debris.




Secrets of Earth's sunken 'lost continent' revealed   Daily Mail - September 27, 2017
Drilling of Zealandia suggests it was closer to land level than thought, and acted as a bridge for animals 80 million years ago. An international team of scientists found fossilized remains and evidence of large-scale tectonic plate shifts as part of one of the first extensive surveys of the region. The discovery of microscopic shells of organisms that lived in warm shallow seas, and spores and pollen from land plants, reveal that the geography and climate of Zealandia was dramatically different in the past.





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