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Drift of continents

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Old cards of both Americas have allowed to find out amazing similarity between coastal lines New and the Old World. There was a question: instead of whether there were once a single whole these continents far lying today from each other?

In the middle of a XIX-th century scientists have started to collect certificates of similarity of fossilized remains (traces of a prehistoric life) in breeds of the continents divided in the big distance. In the XX-th century beginning the American geologist Frenk B. Taylor has come out with the assumption that continents can leave slowly from each other. He believed that drift of continents could cause horizontal (lateral) pressure which has superseded upwards breeds and has transformed them into long mountain ridges.

Teorii Vegenera

Irrespective of Taylor the German meteorologist, the geophysicist and astronomer Alfred Vegener worked. He especially was interested in changes of a global climate throughout the geological period and wished to solve the numerous riddles which have arisen at studying of fossil materials. For example, the fossilized rests of tropical plants have been found under an ice layer and snow in Greenland, and, on the other hand, samples of breeds showed that in olden time glacial boards covered the south of Africa and the South America.

Vegener has given answers to these questions in the book "Die Enstehung der Kontinente und Ozeane" ("¤Ёюшё§юцфхэшх continents and юъхрэют" 1915). He asserted that in those days when tropical plants grew in Greenland, it should settle down near to equator. And when the big spaces of Africa and the South America have been covered by ice, these parts of a land should be round the South Pole. In other words, drift of continents should take place.

However standard the theory of drift of continents became only in 1950-60th years when anybody could not ignore huge data file any more, testifying in its advantage. There was a new term - tectonics of plates. According to the theory of tectonics of plates, continents move with a speed from 1 to 10 sm a year, "ёшф  тхЁ§юь" on huge plates into which it is broken litosfera.

the Mosaic from continents

the Mosaic from continents Primary representations about drift of continents were based on similarity of outlines of Northern and Southern Americas to outlines of Europe and Africa.

However coastal lines are not real borders of continents. Each of them is surrounded by the shallow zone named a continental shelf, actually being part of continent. Their true border passes on top of the abrupt continental slope conducting in abissalnuju a zone (deep sites of ocean). Computer modelling on the basis of continental shelf outlines on depth about 1000 m has shown much more exact coincidence of forms of continents.

One more acknowledgement of drift of continents has been received during studying of rocks, their structure and fossils. For example, Vegener knew that in the past the big glacial ages took place some. At a cold snap of a global climate huge glacial boards (similar to what cover today Antarctica and Greenland) covered the big territories. Glaciers extended by gravity, and the stones which have frozen in in the bottom ice layer, scratched an earth surface, leaving the furrows named glacial shading. Besides, the glacier reserves a moraine - layers of fragments of firm breed, - which forms the adjournment called tillitami.

Structure of rocks

The Structure of rocks also confirmed this theory. So, the majority of breeds in a zone of Sahara in the North Africa have solid age - about 2 billion years. Breeds, which all 550 million years nearby lie. There is very accurate line has undressed between the old and new breeds, reaching coast of Atlantic ocean around Akkra in Ghana. This line is traced and on that party of ocean in the Dignity-luise (Brazil), in accuracy there where supporters of drift of continents predicted. This fact obviously testifies in favour of justice of the given theory. The theory of tectonics of plates has got support and during studying paleomagnetizma that means "фЁхтэшщ ьруэх=шчь". When new breeds were formed of the fused breeds, ferruterous minerals were magnetised. At hardening of liquid breeds these minerals were built in a direction of a magnetic field of the Earth, specifying its site at the moment of formation of breeds. As soon as ore particles hardened in breed, their arrangement was not influenced any more by the further changes of a magnetic zero of the Earth. It means that the magnetic particles which have been found out in rocks, can serve for definition of position of a magnetic pole of the Earth during an epoch of formation of these breeds.

the sea-bottom


the sea-bottom By means of a method of radio isotope dating scientists Testifies have established that the age of any of oceanic breeds did not exceed 200 million years, while most ancient of known continental breeds about 3,8 billion years. Hence, oceans are late formations.

Electronic topographical shooting of an ocean floor has revealed a number of the important signs, including long oceanic ridges for which seismic and volcanic activity is characteristic. In bowels of these ridges find out the youngest oceanic breeds. Geologists are convinced that new breeds are formed in the center of ridges at separation and a distance of plates from each other. They also have found out that in process of removal from ridges there are more and more old breeds forming an oceanic bark.

Four continents

Today scientists know that the terrestrial surface constantly changes. About 420 million years ago kosmoletchik from a far-out planet would see four continents. One of them would be a part of the present North America, the second - a part of modern Europe. The third continent named geologists by Angara, represented then a part of today's Asia, and the fourth united southern continents. Geologists have named it Gondwana.

Moving of plates has led to collision of North American and European continental plates therefore mountain ridges were formed of the breeds crumpled in folds at edges of continents. Northern spurs of Appalachian mountains today concern fragments of this ridge in the North America, mountains in the east of Greenland, in the west of Ireland and Scotland, and also mountain in Norway and Sweden. This new continental file is called as Evramerika.

Raspad Pangei

About 275 million years ago there was a collision of Evrameriki and Angara on which place there were Ural mountains. Then three plates have incorporated, having formed thus a huge part of a land under the name, Lavrazija. In the beginning Lavraziju and Gondwana were divided by the ancient sea Tetis, but soon both continents have incorporated and have formed a uniform continental file - Pangeju.

During last 180 million years Pangeja has broken up, and as a result movings of plates continents have occupied the present position. But moving still proceeds, and scientists can do today assumptions of how our planet in the future will look. Therefore the modern card of the world is only a picture of one moment in geological time of the Earth.