Land bridge

A land bridge, in biogeography, is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonise new lands. A land bridge can be created by marine regression, in which sea levels fall, exposing shallow, previously submerged sections of continental shelf; or when new land is created by plate tectonics; or occasionally when the sea floor rises due to post-glacial rebound after an ice age.

Pm-map
The Isthmus of Panama is a land bridge whose appearance 3 million years ago allowed the Great American Interchange.

Prominent examples

Land bridge theory

In the 19th century a number of scientists noted puzzling geological and zoological similarities between widely separated areas. To solve these problems, "whenever geologists and paleontologists were at a loss to explain the obvious transoceanic similarities of life that they deduced from the fossil records, they sharpened their pencils and sketched land bridges between appropriate continents."[1] The concept was first proposed by Jules Marcou in Lettres sur les roches du Jura et leur distribution géographique dans les deux hémisphères ("Letters on the rocks of the Jura [Mountains] and their geographic distribution in the two hemispheres"), 1857–1860.[2]

The hypothetical land bridges included:[1]

  • Archatlantis from the West Indies to North Africa
  • Archhelenis from Brazil to South Africa
  • Archiboreis in the North Atlantic
  • Archigalenis from Central America through Hawaii to Northeast Asia
  • Archinotis from South America to Antarctica
  • Lemuria in the Indian Ocean
  • Marsupials between South America and Australia.

The concept became obsolete with the gradual acceptance of continental drift and the development of plate tectonics by the mid-20th century.

See also

References

  1. ^ a b Corliss, William R. (June 1975). Mysteries Beneath the Sea. Apollo Editions. ISBN 978-0815203735. Chapter 5: "Up-and-Down Landbridges".
  2. ^ Corliss, William R. (June 1975). Mysteries Beneath the Sea. Apollo Editions. ISBN 978-0815203735. Chapter 5: "Up-and-Down Landbridges". "The basic idea is usually attributed to Jules Marcou..."

External links

Bering Land Bridge National Preserve

The Bering Land Bridge National Preserve is one of the most remote United States national park areas, located on the Seward Peninsula. The National Preserve protects a remnant of the Bering Land Bridge that connected Asia with North America more than 13,000 years ago during the Pleistocene ice age. The majority of this land bridge now lies beneath the waters of the Chukchi and Bering Seas. During the glacial epoch this bridge was a migration route for people, animals, and plants whenever ocean levels fell enough to expose the land bridge. Archeologists disagree whether it was across this Bering Land Bridge, also called Beringia, that humans first migrated from Asia to populate the Americas, or whether it was via a coastal route.Bering Land Bridge National Monument was established in 1978 by Presidential proclamation under the authority of the Antiquities Act. The designation was modified in 1980 to a national preserve with the passage of the Alaska National Interest Lands Conservation Act (ANILCA), which would allow both subsistence hunting by local residents and sport hunting. The preserve includes significant archaeological sites and a variety of geological features. The preserve has seen recent volcanic activity, with lava flows and lake-filled maars. Hot springs are a popular destination for tourists.

Beringia

Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 72 degrees north latitude in the Chukchi Sea; and on the south by the tip of the Kamchatka Peninsula. It includes the Chukchi Sea, the Bering Sea, the Bering Strait, the Chukchi and Kamchatka Peninsulas in Russia as well as Alaska in the United States.

The area includes land lying on the North American Plate and Siberian land east of the Chersky Range. Historically, it formed a land bridge that was up to 1,000 kilometres (620 miles) wide at its greatest extent and which covered an area as large as British Columbia and Alberta together, totaling approximately 1,600,000 square kilometres (620,000 square miles). Today, the only land that is visible from the central part of the Bering land bridge are the Diomede Islands, the Pribilof Islands of St. Paul and St. George, St. Lawrence Island, and King Island.The term Beringia was coined by the Swedish botanist Eric Hultén in 1937. During the ice ages, Beringia, like most of Siberia and all of North and Northeast China, was not glaciated because snowfall was very light. It was a grassland steppe, including the land bridge, that stretched for hundreds of kilometres into the continents on either side.

It is believed that a small human population of at most a few thousand arrived in Beringia from eastern Siberia during the Last Glacial Maximum before expanding into the settlement of the Americas sometime after 16,500 years BP. This would have occurred as the American glaciers blocking the way southward melted, but before the bridge was covered by the sea about 11,000 years BP.Before European colonization, Beringia was inhabited by the Yupik peoples on both sides of the straits. This culture remains in the region today along with others. In 2012, the governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and Beringia National Park in Russia.

Bridge of the Gods (land bridge)

The Bridge of the Gods was a natural dam created by the Bonneville Slide, a major landslide that dammed the Columbia River near present-day Cascade Locks, Oregon in the Pacific Northwest of the United States. The river eventually breached the bridge and washed much of it away, but the event is remembered in local legends of the Native Americans as the Bridge of the Gods.

The Bridge of the Gods is also the name of a modern manmade bridge, across the Columbia River between Oregon and Washington.

Caribbean Plate

The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.

Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis, and volcanic eruptions.

Cross Florida Barge Canal

The Cross Florida Barge Canal, now officially the Marjorie Harris Carr Cross Florida Greenway is a protected green belt corridor, one mile (1.6 km) wide in most places. It is named for the leader of opposition to the Cross Florida Barge Canal, a canal project to connect the Gulf of Mexico and the Atlantic Ocean across Florida for barge traffic. Two sections were built but the project was cancelled, mainly for environmental reasons.

The Greenway includes the Santos Trail System.

Dostyk

Dostyk (Kazakh: Достық, Dostyq) or Druzhba (Russian: Дружба) is a small town in Kazakhstan's Almaty Region, on the border with Xinjiang, China. It is a port of entry (by highway and railroad) from China. The rail portion serves as an important link in the Eurasian Land Bridge. It is situated in the Dzungarian Gate, a historically significant mountain pass.

Eurasia Continental Bridge passageway

The Eurasia Continental Bridge passageway (simplified Chinese: 陆桥通道; traditional Chinese: 陸橋通道; pinyin: Lùqiáo Tōngdào) is a high-speed rail corridor connecting Lianyungang, a port in northern Jiangsu province, to Ürümqi, the regional capital of Xinjiang. The corridor passes through the cities of Xuzhou (Jiangsu), Zhengzhou (Henan), Xi'an (Shaanxi), Lanzhou (Gansu), and Xining (Qinghai) en route. Announced in 2016 as part of the "eight verticals and eight horizontals" railway network plan, the rail corridor is an extension of the existing Xuzhou–Lanzhou high-speed railway.

The railway may be considered to be part of the New Eurasian Land Bridge.

Eurasian Land Bridge

The Eurasian Land Bridge (Russian: Евразийский сухопутный мост, Yevraziyskiy sukhoputniy most), sometimes called the New Silk Road (Новый шёлковый путь, Noviy shyolkoviy put'), or Belt and Road Initiative is the rail transport route for moving freight and passengers overland between Pacific seaports in the Russian Far East and China and seaports in Europe. The route, a transcontinental railroad and rail land bridge, currently comprises the Trans-Siberian Railway, which runs through Russia and is sometimes called the Northern East-West Corridor, and the New Eurasian Land Bridge or Second Eurasian Continental Bridge, running through China and Kazakhstan. As of November 2007, about 1% of the $600 billion in goods shipped from Asia to Europe each year were delivered by inland transport routes.Completed in 1916, the Trans-Siberian connects Moscow with Russian Pacific seaports such as Vladivostok. From the 1960s until the early 1990s the railway served as the primary land bridge between Asia and Europe, until several factors caused the use of the railway for transcontinental freight to dwindle. One factor is that the railways of the former Soviet Union use a wider rail gauge than most of the rest of Europe as well as China. Recently, however, the Trans-Siberian has regained ground as a viable land route between the two continents.China's rail system had long linked to the Trans-Siberian via northeastern China and Mongolia. In 1990 China added a link between its rail system and the Trans-Siberian via Kazakhstan. China calls its uninterrupted rail link between the port city of Lianyungang and Kazakhstan the New Eurasian Land Bridge or Second Eurasian Continental Bridge. In addition to Kazakhstan, the railways connect with other countries in Central Asia and the Middle East, including Iran. With the October 2013 completion of the rail link across the Bosphorus under the Marmaray project the New Eurasian Land Bridge now theoretically connects to Europe via Central and South Asia.

Proposed expansion of the Eurasian Land Bridge includes construction of a railway across Kazakhstan that is the same gauge as Chinese railways, rail links to India, Burma, Thailand, Malaysia and elsewhere in Southeast Asia, construction of a rail tunnel and highway bridge across the Bering Strait to connect the Trans-Siberian to the North American rail system, and construction of a rail tunnel between South Korea and Japan. The United Nations has proposed further expansion of the Eurasian Land Bridge, including the Trans-Asian Railway project.

Intermodal freight transport

Intermodal freight transport involves the transportation of freight in an intermodal container or vehicle, using multiple modes of transportation (e.g., rail, ship, and truck), without any handling of the freight itself when changing modes. The method reduces cargo handling, and so improves security, reduces damage and loss, and allows freight to be transported faster. Reduced costs over road trucking is the key benefit for inter-continental use. This may be offset by reduced timings for road transport over shorter distances.

Island

An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines.

An island may be described as such, despite the presence of an artificial land bridge; examples are Singapore and its causeway, and the various Dutch delta islands, such as IJsselmonde. Some places may even retain "island" in their names for historical reasons after being connected to a larger landmass by a land bridge or landfill, such as Coney Island and Coronado Island, though these are, strictly speaking, tied islands. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal or Marble Hill in northern Manhattan during the time between the building of the United States Ship Canal and the filling-in of the Harlem River which surrounded the area, it is generally not considered an island.

There are two main types of islands in the sea: continental and oceanic. There are also artificial islands.

Isthmus

An isthmus ( or ; plural: isthmuses; from Ancient Greek: ἰσθμός, romanized: isthmós, lit. 'neck') is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea counterpart of an isthmus.

Canals are often built across isthmuses, where they may be a particularly advantageous shortcut for marine transport. For example, the Panama Canal crosses the Isthmus of Panama, connecting the North Atlantic and Pacific Oceans; the Suez Canal connects the Mediterranean Sea and the Red Sea, cutting across the western side of the Isthmus of Suez, formed by the Sinai Peninsula; and the Crinan Canal crosses the isthmus between Loch Crinan and Loch Gilp, which connects the Kintyre peninsula with the rest of Scotland. Another example is the Welland Canal in the Niagara Peninsula (technically an isthmus). It connects Lake Ontario to Lake Erie. The city of Auckland in the North Island of New Zealand is situated on an isthmus.

List of companies of Egypt

Egypt is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia by a land bridge formed by the Sinai Peninsula. Egypt's economy depends mainly on agriculture, media, petroleum imports, natural gas, and tourism; there are also more than three million Egyptians working abroad, mainly in Saudi Arabia, the Persian Gulf and Europe. The completion of the Aswan High Dam in 1970 and the resultant Lake Nasser have altered the time-honoured place of the Nile River in the agriculture and ecology of Egypt. A rapidly growing population, limited arable land, and dependence on the Nile all continue to overtax resources and stress the economy.For further information on the types of business entities in this country and their abbreviations, see "Business entities in Egypt".

List of railway lines in China

The following is a list of rail transport in China.

Marine transgression

A marine 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). Transgressions and regressions may be caused by tectonic events such as orogenies, severe climate change such as ice ages or isostatic adjustments following removal of ice or sediment load.

During the Cretaceous, seafloor spreading created a relatively shallow Atlantic basin at the expense of deeper Pacific basin. This reduced the world's ocean basin capacity and caused a rise in sea level worldwide. As a result of this sea level rise, the oceans transgressed completely across the central portion of North America and created the Western Interior Seaway from the Gulf of Mexico to the Arctic Ocean.

The opposite of transgression is regression, in which the sea level falls relative to the land and exposes former sea bottom. During the Pleistocene Ice Age, so much water was removed from the oceans and stored on land as year-round glaciers that the ocean regressed 120 m, exposing the Bering land bridge between Alaska and Asia.

New Eurasian Land Bridge

The New Eurasian Land Bridge, also called the Second or New Eurasian Continental Bridge, is the southern branch of the Eurasian Land Bridge rail links running through China. The Eurasian Land Bridge is the overland rail link between Asia and Europe.

Pseudothelphusidae

Pseudothelphusidae is a family of freshwater crabs found chiefly in mountain streams in the Neotropics. They are believed to have originated in the Greater Antilles and then crossed to Central America via a Pliocene land bridge.

Settlement of the Americas

The first settlement of the Americas began when Paleolithic hunter-gatherers first entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the Last Glacial Maximum.

These populations expanded south of the Laurentide Ice Sheet and rapidly throughout both North and South America, by 14,000 years ago. The earliest populations in the Americas, before roughly 10,000 years ago, are known as Paleo-Indians.

The peopling of the Americas is a long-standing open question, and while advances in archaeology, Pleistocene geology, physical anthropology, and DNA analysis have shed progressively more light on the subject, significant questions remain unresolved. While there is general agreement that the Americas were first settled from Asia, the pattern of migration, its timing, and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear. In 2019, a study by the University of Cambridge and University of Copenhagen concluded that Native Americans are the closest relatives to the 10,000-year-old inhabitants of the Kolyma River in northeastern Siberia.The prevalent migration models outline different time frames for the Asian migration from the Bering Straits and subsequent dispersal of the founding population throughout the continent. Indigenous peoples of the Americas have been linked to Siberian populations by linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.The "Clovis first theory" refers to the 1950s hypothesis that the Clovis culture represents the earliest human presence in the Americas, beginning about 13,000 years ago; evidence of pre-Clovis cultures has accumulated since 2000, pushing back the possible date of the first peopling of the Americas to about 13,200–15,500 years ago.

Seward Peninsula

The Seward Peninsula is a large peninsula on the western coast of the U.S. state of Alaska. It projects about 320 kilometers (200 mi) into the Bering Sea between Norton Sound, the Bering Strait, the Chukchi Sea, and Kotzebue Sound, just below the Arctic Circle. The entire peninsula is about 330 kilometers (210 mi) long and 145 km (90 mi)-225 km (140 mi) wide. Like Seward, Alaska, it was named after William H. Seward, the United States Secretary of State who fought for the U.S. purchase of Alaska.

The Seward Peninsula is a remnant of the Bering land bridge, a roughly thousand mile wide swath of land connecting Siberia with mainland Alaska during the Pleistocene Ice Age. This land bridge aided in the migration of humans, as well as plant and animal species, from Asia to North America. Excavations at sites such as the Trail Creek Caves and Cape Espenberg in the Bering Land Bridge National Preserve as well as Cape Denbigh to the south have provided insight into the timeline of prehistorical migrations from Asia to the Seward Peninsula.

Sideros

Sideros (Greek: Σίδερος, "iron"), also known as Strongylo (Greek: Στρογγύλο, "round"), is an uninhabited Greek rock, in the Aegean Sea, close to the northeastern coast of eastern Crete. The rock lies just north of the peninsula of Kyriamadi, with which it is connected by a small land bridge. There is also a Cape Sideros on the island of Kyriamadi. Administratively it lies within the Itanos municipality of Lasithi.

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