Everything about Landbridge totally explained
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. 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 (for example 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 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.
Further Information
Get more info on 'Landbridge'.
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