Land Bridge

Information about Land Bridge

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 (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 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).

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.

A transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water (or decreasing in capacity).
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continental shelf is the extended perimeter of each continent and associated coastal plain, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs.
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"Oeland".

For the German island, see .

For the Finnish island, see .

Öland (help info )
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Motto
(Royal) "För Sverige - I tiden" ¹
"For Sweden – With the Times" ²
Anthem
Du gamla, Du fria
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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 and Asia. Very broadly it dates to between 40,000 and 10,000 years ago, roughly coinciding with the appearance of "high"
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Sea-level rise is an increase in sea level. Multiple complex factors may influence this change.

Sea-level has risen about 130 metres (400 feet) since the peak of the last ice age about 18,000 years ago. Most of the rise occurred before 6,000 years ago.
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Global warming refers to the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.

The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.
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glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water.
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Bering land bridge, also known as Beringia, was a land bridge roughly 1,000 miles (1,600 km) north to south at its greatest extent, which joined present-day Alaska and eastern Siberia at various times during the Pleistocene ice ages.
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Eurasia is an immense landmass covering about 53,990,000 km² (or about 10.6%) of the Earth's surface. Often reckoned as 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
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Americas are the lands of the Western hemisphere or New World consisting of the continents of North America^[1] and South America with their associated islands and regions. The Americas cover 8.3% of the Earth's total surface area (28.
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There are several popular models of migration to the New World proposed by the anthropological community. The question of how, when and why humans first entered the Americas is of serious interest to anthropologists and has been a subject of heated debate for centuries.
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Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth's lithosphere.
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A geologic formation is a formally named rock stratum or geological unit. Formations are Lithostratigraphic units which are defined by primary lithology.

The concept of formally defined layers or strata is central to the geologic discipline of stratigraphy.
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Lemuria (IPA: /lɨˈmjʊəriə/^[1]) is the name of a hypothetical "lost land" variously located in the Indian and Pacific Oceans.
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Atlantic Ocean is the second-largest of the world's oceanic divisions; with a total area of about 106.4 million square kilometres (41.1 million square miles), it covers approximately one-fifth of the Earth's surface.
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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.
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Alfred Lothar Wegener (Berlin, November 1, 1880 – Greenland, November 2 or 3, 1930) was a German interdisciplinary scientist and meteorologist, who became famous for his theory of continental drift ("Kontinentalverschiebung" or "die Verschiebung der Kontinente" in his words).
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Continental drift refers to the movement of the Earth's continents relative to each other.

Frank Bursley Taylor had proposed the concept in a Geological Society of America meeting in 1908 and published his work in the GSA Bulletin in June 1910.
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This article is about the cultural and social sciences term mainstream. For the Hugo-nominated fanzine, see Mainstream (fanzine). For the record label, see Mainstream Records.

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Oceanic crust 0-20 Ma
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Habitat fragmentation is a process of environmental change important in evolution and conservation biology. As the name implies, it describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat).
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