Continental drift

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The theory of continental drift , also known as continental drift , describes the slow movement, division and unification of continents . The first hypotheses on continental drift led to a gradual move away from fixism towards mobilism in the 18th and 19th centuries . The movement of the continents is now part of the theory of plate tectonics .

Continental drift over the last 250 million years


The causative forces are currently still in dispute, but the geodynamic findings are clear. The satellite geodesy and modern geodetic earth models indicate almost all continental margins annual movement rates, which range from one to about ten centimeters. Some inner-continental fault lines , for example in the Mediterranean region and in East Africa, show recent shifts.

Instead of plate tectonics , one speaks of plate kinematics when it comes to purely geometric models of the earth's crustal movements , in which the causative forces are not taken into account. These kinematic models currently show fewer discrepancies than their dynamic counterparts (e.g. NUVEL ) and are therefore already suitable as reference systems for global coordinate changes. The best known is the international reference framework of the ITRF , which has been adjusted to current continental drifts every one to two years since 2000.

History of theory

First hypotheses (17th / 18th century)

The most obvious and therefore the earliest recognized indication of continental drift is the similarity over the course of the west coast of Africa and the east coast of South America .

The oldest assumption of continental drift as the cause comes from the Flemish cartographer Abraham Ortelius . In the edition of his Atlas Theatrum Orbis Terrarum from 1596, the similarity of the two coastlines can already be seen.

Often the first reference is also ascribed to Sir Francis Bacon in 1620; but Bacon is said to have referred only to the similarity of the west coasts of both continents, that is, the Atlantic coast of Africa and the Pacific coast of South America. In contrast, the theology professor Theodor Christoph Lilienthal in Königsberg, in view of the similarity of the opposite coasts of South America and Africa, considered the possibility in 1756 that they were once close to each other. He associated the breakup with the biblical flood .

Even Benjamin Franklin set out in 1782 in a letter to the French geologist Jean-Louis Giraud-Soulavie thoughts about continental drift:

“Such changes in the outer areas of the earth seemed unlikely to me if the earth were solid to the center. I therefore imagined that the inner areas could be a liquid of much higher density and specific gravity than any of the solid substances we know and that therefore the outer areas float on or in the liquid. The surface of the earth would then be a shell that could break and become disordered due to the violent movements of the liquid on which it floats ... "

Antonio Snider-Pellegrini's depiction of the closed and open Atlantic (1858)

From flood and moon theories to Eduard Suess

In 1801 and 1845, Alexander von Humboldt described the similarity of the opposite coasts of South America and Africa and their vegetation and speculated that the Atlantic was washed out by a catastrophic current. In 1858, the geographer Antonio Snider-Pellegrini went one step further when he published the first map showing the Old and New Worlds without a separating ocean. He also speculated that the Flood was the reason for the separation. At the turn of the century , the drifting apart of the American and African continents was associated with the emergence of the moon from the Pacific.

The Austrian geologist Eduard Suess (1831–1914) initially represented the land bridge theory in his book series "Das Antlitz der Erde" in order to explain the striking similarities between certain fossil animal and plant communities on different continents today. However, he later postulated the existence of two previously contiguous large land masses. For the southern part of the two, Suess coined the name Gondwana -Land, which had been introduced by others . In the Mesozoic era, this continent comprised all of today's continents in the southern hemisphere, including India. At the beginning of the Cenozoic, however, large parts of this continent sank and became oceans.

Alfred Wegener and his opponents

Wegener's immediate predecessor

These models, which are part of fixism , assume that the earth's crust is firmly connected to the subsurface. Especially through the work of Alfred Wegener (1912, 1915) these models were abandoned in favor of a different view of the shifting of the continents (mobilism). Wegener himself stated in 1929 that others had the idea of ​​continental drift as the movement of parts of the earth's crust before him, even if not in as elaborate a form as he did. He emphasized that he had gained his own ideas independently of those of his predecessors. These predecessors mentioned by Wegener include Franklin Coxworthy (between 1848 and 1890), Roberto Mantovani (between 1889 and 1909), William Henry Pickering (1907) and Frank Bursley Taylor (1908), who postulated the breakup of the continents .

As Wegener noted, Roberto Mantovani's maps, on which the original grouping of the continents are shown, agree in part "astonishingly" with his own. Wegener did not mention, however, that Mantovani did not proceed directly from a drift of the continents, but from an expansion of the oceanic areas between the continents in the sense of the competing theory of earth expansion . The theory of plate tectonics developed in the 1960s supports the idea of ​​the formation of new oceanic crusts through ocean floor spreading , but assumes that the crust descends into the mantle at some continental margins ( subduction ) and thus a constant earth radius, although the conclusion is ocean floor spreading and subduction would have to balance each other quantitatively, from the fact that subduction at certain continental margins cannot necessarily be deduced.

Wegener's theory of Frank Bursley Taylor is described as particularly similar , who on December 29, 1908, claimed in a lecture to the Geological Society of America that, in contrast to Mantovani, the continents had slowly drifted apart at a constant earth radius . Wegener particularly referred to Taylor's description of the development of the Atlantic and the separation of Greenland from North America . The theory of continental drift was therefore earlier known in America as the "Taylor-Wegener theory", with Taylor later becoming one of Wegener's first followers.

Alfred Wegener

The paleobiogeographical distribution areas of Cynognathus , Mesosaurus , Glossopteris and Lystrosaurus shown here in color (highly schematic and not identical to the actual distribution areas that can be reconstructed on the basis of the fossil sites) allow the reconstruction of Gondwana and are therefore evidence of the existence of plate tectonics

In his book The Origin of Continents and Oceans , published in 1915, Wegener concluded from the precise fit of the coastlines of South America and Africa that these could have been fragments of a formerly larger continent that had broken apart in the geological past. The fit is even more accurate if one does not consider the coastlines but the shelf edges , i.e. the submerged parts of a continent. In contrast to his predecessors, Wegener succeeded in substantiating his theory through various studies in the various branches of geosciences. These include the following arguments collected by Wegener:

  • Fold belts and shear zones from South America can be compared in Africa with very similar rock sequences and deformation patterns.
  • Diamond deposits in South America and West Africa share geological similarities.
  • On all southern continents there are air -Zeugen of the Permo-Carboniferous ice age , including rectified glacial grinding marks.
  • Certain fossil and recent flora and fauna on both sides of the Atlantic agree:
    • Fossils of cold- loving land plants with tongue-shaped leaves ( Glossopteris flora ) were widespread on all southern continents.
    • Fossil remains of Mesosaurus , a freshwater reptile, have been found in both Africa and South America.
    • The manatees are found in West Africa as well as in Central and South America.

Using such clues, Wegener reconstructed a supercontinent, which he named Pangea - All Land - which included not only the southern continents but all known continental masses. According to his theory, the specifically lighter continental crust or "SiAl", consisting predominantly of granitic rock - in addition to silicon, aluminum is the predominant element of granite - should be placed on the denser, basaltic subsoil, the "SiMa" - the aluminum is represented in the basalt by magnesium - "swim", like an iceberg drifting in the sea.

As a possible force that caused the continents to break up and drift apart, Wegener suggested various astronomical forces: for example, the slowing down of the earth's rotation by the tidal friction of the moon, precession and tidal forces. The “ pole flight ”, ie the centrifugal force generated by the earth's rotation, should move the continental masses “floating” on the earth's mantle slowly towards the equator. This hypothesis was elaborated by Paul Sophus Epstein in 1920, but was soon refuted.

The theory of continental drift did not catch on for a long time, which was due to the lack of a plausible explanation of the shifts. The explanations by Mantovani (movement as the result of earth expansion due to thermal expansion ), Taylor (movement due to tidal forces due to the approach of the moon 100 million years ago) and Wegener (movement due to centrifugal force and tidal force ) turned out to be wrong. It was not until the investigation of plate tectonics from 1960 onwards that continental drift was generally recognized. A less scientific motive of Wegener's opponents was possibly the conflicts between the then strictly separated sub-fields of geosciences . Since Wegener had originally dealt with astronomy , meteorology and climatology , he was considered by many "real" geologists as an unqualified "career changer".

Basic concept of continental drift

Of particular interest are those periods of the earth's history in which all continents were united to form a land mass or in which the so-called supercontinent broke up again. One also speaks of supercontinent cycles, five or six of which are postulated in the course of the earth's history. However, only the last (known as Pangea ) and the penultimate (known as Rodinia or Vendium) supercontinent are generally accepted. If the current continent movement continues unabated, Australia will collide with Asia in about 60 million years and a new supercontinent, sometimes called Pangea ultima , can be expected in about 300 million years .

The geological layers that emerged between the Permian and Jurassic allow the reconstruction of the supercontinent Pangea, which was broken up at the time. In contrast, the reconstruction of Rodinia, which broke up at the end of the Precambrian , is less well established.

For the mechanisms of the process, see plate tectonics

The mainland masses in
Unterperm, united to form Pangea

Plate shifts in the past

It is well known how fast and where the large plates are currently moving, and various clues allow us to reconstruct their paths in the past. Because of their inertia, it takes tens of millions of years to come to a standstill and even longer to reverse their movement.

  • It is believed that around 320 million years ago the earth's land mass essentially comprised two continents , namely Gondwana and Laurasia .
  • Around 250 million years ago, the two had grown together to form the giant continent of Pangea , which was surrounded by the giant ocean Panthalassa and into which the Tethys stretched like a huge bay from the east .
  • The continental mass broke up about 135 million years ago. The Tethys opened further to the west and separated a southern continent, which is again referred to as Gondwana. The northern continent split into two parts, North America and Eurasia , when the North Atlantic opened .
  • The continent's process of decay continued until around 100 million years ago. The great southern continent in particular has split into South America , Africa , India , Antarctica and Australia . The Tethys still separates the northern continents from the southern continents.

Plate shifts in the future

All geological observations indicate that the plates are still dynamic.

Forecasts for continents

India will slide under the Himalayas for some time and perhaps disappear completely under Tibet . In return, the elevations of the Mongolian Plateau will continue to grow in the north and finally an extensive mountain range will advance to Lake Baikal .

Great changes are to be expected off Australia , which is rapidly drifting north and is likely to slide under the Sunda Islands . These then grow up into a new mountain range that slides onto the Australian plate.

Along the lake district of the East African Rift , the southern part of the Great Rift Valley , the formation of a new ocean can be observed that will connect with the Red Sea . As a result, a new continental plate will split off from Africa and drift further east. The rift valley will then become a new mid-ocean ridge .

The Atlantic will continue to open along the mid-Atlantic ridge. In return, the Pacific will gradually shrink and disappear completely in the distant future. The Pacific is a remnant of Panthalassa - the ocean that is believed to have surrounded the supercontinent Pangea , but there is no geological evidence of its previous existence. The mid-ocean ridge of the North Pacific , the East Pacific Ridge, was subducted under North America . This process is imminent off South America . It can be assumed that this will continue.

Extrapolation in seven stages

It cannot be precisely predicted how the land masses will be distributed on the earth's surface in 200 million years. An extrapolation of the current movements gives the following picture:

In 20 million years
will East Africa along the East African grave breach of the rest of Africa split off, while a new ocean form. The Iberia (essentially the Iberian Peninsula ) separates from Europe , turning slightly clockwise. Australia and New Zealand are rapidly pushing northward, so that Northern Australia is now on the equator . The Black Sea is completely cut off from the Mediterranean Sea and the Gulf of Aqaba has opened up to Turkey .
In 40 million years
is Africa continues to migrate to the north and the Mediterranean region completely remodel, Sicily is shifted to the north and is located near the coast in front of Rome . Iberia continues to turn clockwise away from Europe. Europe could fall apart along the Rhine . Australia continues to migrate towards Southeast Asia . The Atlantic is getting wider as America moves further away from Europe and Africa.
In 50 million years
Baja California breaks away from mainland America along the San Andreas Fault and migrates northeast. North America with Greenland initially moves west, then turns clockwise and drifts south. This is how Greenland enters the temperate zone south of the 60th parallel.
In 80 million years
Africa will have advanced so far north that, as a result of the thrust, a new mountain range will gradually have taken the place of the Mediterranean . Australia has now collided with Japan , New Zealand has reached the tropics and Antarctica is headed for Australia.
In 90 million years
North and South America are separated. North America shifts south to the side of South America.
In 150 million years
Greenland, south of present-day Peru, is about 30 degrees south latitude.
In 200 million years
Antarctica has come so close to Mexico that both are located on the equator and Antarctica will be lush, as it was last in the early Mesozoic . East Africa collides with India , Madagascar meets Southeast Asia. Newfoundland is already at 10 degrees north latitude and continues towards the equator that Florida has already left behind on its way south. South America has rotated 90 degrees clockwise. For the past 200 million years, Scandinavia and the British Isles have slowly moved in a southeastern direction.


  • Frank Press , Thomas H. Jordan, Raymond Siever , John P. Grotzinger : General Geology. 5th edition. Spectrum Academic Publishing House, Heidelberg / Berlin 2008, ISBN 978-3-8274-1812-8 . (Original title: Understanding Earth, Freeman, New York, NY, 1993, translated by Volker Schweizer).
  • Rainer Kind, Xiaohui Yuan: Colliding Continents . In: Physics in Our Time . tape 34 (5) . Wiley-VCH, 2003, ISSN  0031-9252 , pp. 213-217 .

Web links


Individual evidence

  1. James Romm: A new forerunner for continental drift. In: nature. 367, Feb. 3, 1994, pp. 407-408.
  2. After Philip Kearey, Frederick J. Vine: Global Tectonics. Blackwell Scientific Publications, Oxford 1990.
  3. A. Wegener: The emergence of the continents . In: Peterm. Mitt . 1912, p. 185-195, 253-256, 305-309 .
  4. A. Wegener: The emergence of the continents and oceans . 4th edition. Friedrich Vieweg & Son, Braunschweig 1929.
  5. ^ F. Coxworthy: Electrical Condition or How and Where our Earth was created. WJS Phillips, London 1848/1924.
  6. ^ WH Pickering: The Place of Origin of the Moon - The Volcani Problems . In: Popular Astronomy . 1907, p. 274-287 , bibcode : 1907PA ..... 15..274P .
  7. ^ G. Scalera: Roberto Mantovani an Italian defender of the continental drift and planetary expansion . In: G. Scalera, K.-H. Jacob (Ed.): Why expanding Earth? - A book in honor of OC Hilgenberg . Istituto Nazionale di Geofisica e Vulcanologia, Rome 2003, p. 71-74 .
  8. ^ FB Taylor: Bearing of the tertiary mountain belt on the origin of the earth's plan . In: GSA Bulletin . tape 21 , no. 2 , 1910, pp. 179-226 .
  9. ^ G. Hofbauer: Alfred Wegener - Drifting continents and immobile geologists. (PDF; 633 kB).
  10. See interactive geological map ( memento of the original from October 8, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. the Smithsonian Institution . The current movements of the plates are shown with arrows if the Plate Tectonics menu item is activated in the Layers menu . @1@ 2Template: Webachiv / IABot /