Plates in the crust of the earth, according to the plate tectonics theory

Continental drift refers to the movement of the Earth's continents relative to each other. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912. Abraham Ortelius ( Abraham Ortels) ( April 2, 1527 – June 28, 1598) was a Belgian Cartographer and Alfred Lothar Wegener ( November 1, 1880 – November 2 or 3 1930 was a German Scientist and Meteorologist. However, only with the development of the theory of plate tectonics in the 1960s a sufficient geological explanation of the cause of their movement could be found. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit (This article gives an overview about the development of the continental drift hypothesis before 1950. For the contemporary theory, see the article plate tectonics. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere )

History

Early history

Antonio Snider-Pellegrini's Illustration of the closed and opened Atlantic Ocean (1858).

Abraham Ortelius (1596), Francis Bacon (1620), Benjamin Franklin, Antonio Snider-Pellegrini (1858), and others had noted earlier that the shapes of continents on either side of the Atlantic Ocean (most notably, Africa and South America) seem to fit together. Abraham Ortelius ( Abraham Ortels) ( April 2, 1527 – June 28, 1598) was a Belgian Cartographer and Francis Bacon 1st Viscount St Alban KC QC (22 January 1561 – 9 April 1626 was an English Philosopher, Statesman, and author Benjamin Franklin ( April 17 1790 was one of the Founding Fathers of the United States of America. Antonio Snider-Pellegrini (1802-1885 was a French Geographer and scientist who theorized about the possibility of Continental drift, anticipating A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions W. J. Kious described Ortelius' thoughts in this way:^[1]

Wegener and his predecessors

The hypothesis that the continents once formed a single landmass, broke up, and drifted to their present locations was fully elaborated by Alfred Wegener in 1912. Alfred Lothar Wegener ( November 1, 1880 – November 2 or 3 1930 was a German Scientist and Meteorologist. ^[2] Although Wegener's theory was formed independently and was more complete than those of his predecessors, Wegener would later credit a number of past authors with similar ideas: ^{[3] [4]} Franklin Coxworthy (between 1848 and 1890), ^[5] Roberto Mantovani (between 1889 and 1909), William Henry Pickering (1907) ^[6] and Frank Bursley Taylor (1908). Roberto Mantovani ( March 25 1854 &ndash January 10 1933) was an Italian Geologist and Violinist. William Henry Pickering ( February 15, 1858 &ndash January 17, 1938) was an American Astronomer, brother of Edward Frank Bursley Taylor (1860 &ndash 1938 was a wealthy amateur American Geologist, a specialist in the Glacial geology of the Great Lakes, and proposed

For example: The similarity of southern continent geological formations had led Roberto Mantovani to conjecture in 1889 and 1909 that all the continents had once been joined into a supercontinent (now known as Pangaea). Roberto Mantovani ( March 25 1854 &ndash January 10 1933) was an Italian Geologist and Violinist. In Geology, a supercontinent is a Landmass comprising more than one Continental core or Craton. Pangaea, Pangæa or Pangea (pænˈdʒiːə from παν pan, meaning entire, and Γαῖα Gaea, meaning Earth in (Regarding the former positions of the southern continents, Wegener himself also noted the similarity of Mantovani's and his own maps). Through volcanic activity because of thermal expansion this continent broke, whereby the new continents were drifting away from each other because of further expansion of the rip-zones, where now the oceans lie. Plate tectonics and hotspots Divergent plate boundaries At the Thermal Expansion is the tendency of matter to change in Volume in response to a change in temperature However, this led Mantovani to propose an Expanding Earth theory, which is now considered to be superseded. The Expanding Earth theory is an attempt to explain the position and movement of Continents ( Continental drift) on the surface of the Earth ^{[7] [8] [9]} Some sort of continental drift at constant earth radius was proposed by Frank Bursley Taylor, who suggested in 1908 (published in 1910) that the continents were dragged towards the equator by increased lunar gravity during the Cretaceous, thus forming the Himalaya and Alps on the southern faces. Frank Bursley Taylor (1860 &ndash 1938 was a wealthy amateur American Geologist, a specialist in the Glacial geology of the Great Lakes, and proposed The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Wegener said that from all those theories, Taylor's theory (although not fully developed) had the most similarities to his own theory. ^[10]

Wegener was the first to use the phrase "continental drift" (1912, 1915) ^{[2] [3]} (in German "die Verschiebung der Kontinente") and formally publish the hypothesis that the continents had somehow "drifted" apart. And although he presented much evidence for continental drift, he was unable to provide a convincing explanation for the physical processes which might have caused this drift. His suggestion that the continents had been pulled apart by the centrifugal pseudoforce of the Earth's rotation was considered unrealistic by the scientific community. ^[11]

Controversial years

Wegener's hypothesis received support through the controversial years from South African geologist Alexander Du Toit as well as from Arthur Holmes. The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa Alexander Logie du Toit ("DOO-TOY" ( 14 March 1878 &ndash 25 February 1948) was a Geologist from South Africa Arthur Holmes ( January 14 1890 &ndash September 20 1965) was a British Geologist. The idea of continental drift did not become widely accepted even as theory until the late 1950s. The word theory has many distinct meanings in different fields of Knowledge, depending on their methodologies and the context of discussion. By the 1960s, geological research conducted by Robert S. Dietz, Bruce Heezen, and Harry Hess, along with a rekindling of the theory including a mechanism by J. Tuzo Wilson led to widespread acceptance of the theory among geologists. Robert Sinclair Dietz ( September 14, 1914 &ndash May 19, 1995) was Professor of Geology at Arizona State University. Bruce Charles Heezen ( April 11, 1924 – June 21, 1977) was an American geologist Harry Hammond Hess ( May 24, 1906 – August 25, 1969) was a Geologist and United States Navy officer in World War John Tuzo Wilson PhD, CC, OBE, DSc, FRS, FRSC, FRSE ( October 24, 1908 &ndash

Evidence

For more details on this topic, see Plate tectonics. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere

Note: This section contains evidence available to Wegener's contemporaries and predecessors

Fossil patterns across continents.

Pangaea separation animation

The notion that continents have not always been at their present positions was suggested as early as 1596 by the Dutch map maker Abraham Ortelius in the third edition of his work Thesaurus Geographicus. Abraham Ortelius ( Abraham Ortels) ( April 2, 1527 – June 28, 1598) was a Belgian Cartographer and Ortelius suggested that the Americas, Eurasia and Africa were once joined and have since drifted apart "by earthquakes and floods", creating the modern Atlantic Ocean. For evidence, he wrote: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three continents. " Francis Bacon commented on Ortelius' idea in 1620, as did Benjamin Franklin and Alexander von Humboldt in later centuries. Francis Bacon 1st Viscount St Alban KC QC (22 January 1561 – 9 April 1626 was an English Philosopher, Statesman, and author Benjamin Franklin ( April 17 1790 was one of the Founding Fathers of the United States of America. (September 14 1769 &ndash May 6 1859 was a German naturalist and explorer, and the younger brother of the Prussian minister philosopher and linguist

Evidence for continental drift is now extensive, in the form of plant and animal fossils of the same age found around different continent shores, suggesting that these shores were once joined: the fossils of the freshwater crocodile, found in Brazil and South Africa, are one example. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. A crocodile is any Species belonging to the family Crocodylidae (sometimes classified instead as the Subfamily Crocodylinae) |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa Another is the discovery of fossils of the aquatic reptile Lystrosaurus from rocks of the same age from locations in South America, Africa, and Antarctica. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Lystrosaurus (meaning 'shovel lizard' pronunciation in ˌlɪstrɒˈsɔrəs was a Genus of Late Permian and Early Triassic Period In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a There is also living evidence — the same animals being found on two continents. An example of this is a particular earthworm found in South America and South Africa. Earthworm is the usual name for the largest members of Oligochaeta (which is either a class or subclass depending on the author in the phylum Annelida In classical

The complementary arrangement of the facing sides of South America and Africa is obvious, but is a temporary coincidence. In millions of years, seafloor spreading, continental drift, and other forces of tectonophysics will further separate and rotate those two continents. Tectonophysics, a branch of Geophysics, is the study of rock deformation and of dynamic geophysical processes It was this temporary feature which inspired Wegener to study what he defined as continental drift. He never lived to see his hypothesis be proven true.

Widespread distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia was one of the major pieces of evidence for the theory of continental drift. The Permo-Carboniferous refers to the time period including the latter parts of the Carboniferous and early part of the Permian period The continuity of glaciers, inferred from oriented glacial striations and deposits called tillites, suggested the existence of the supercontinent of Gondwana, which became a central element of the concept of continental drift. Striations means a series of Ridges, furrows or Linear marks and are used in several ways Glacial striation Striation (geology Till is unsorted glacial sediment Glacial drift is a general term for the coarsely graded and extremely heterogeneous Sediments of glacial origin Gondwana (ɡɒnˈdwɑːnə originally Gondwanaland) was a southern Supercontinent that existed about 500 to 200 Ma ago Striations indicated glacial flow away from the equator and toward the poles, in modern coordinates, and was a good indicator of the fact that the southern continents had previously been in dramatically different locations, as well as contiguous with each other.

Debate

Before geophysical evidence started accumulating after World War II, the idea of continental drift caused sharp disagreement among geologists. Geophysics, a major discipline of Earth sciences, is the study of the Earth by quantitative physical methods especially by seismic, electromagnetic World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Wegener had introduced his theory in 1912 at a meeting of the German Geological Association. His paper was published that year and expanded into a book in 1915. In 1921 the Berlin Geological Society held a symposium on the theory. In 1922 Wegener's book was translated into English and then it received a wider audience. In 1923 the theory was discussed at conferences by Geological Society of France, the Geological Section of the British Association for the Advancement of Science, and the Royal Geological Society. The theory was carefully but critically reviewed in the journal Nature by Philip Lake. ^[12] On November 15, 1926, the American Association of Petroleum Geologists (AAPG) held a symposium at which the continental drift hypothesis was vigorously debated. Events 655 - Battle of Winwaed: Penda of Mercia is defeated by Oswiu of Northumbria. Year 1926 ( MCMXXVI) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar. The American Association of Petroleum Geologists (or AAPG) is one of the world's largest professional geological societies with over 31000 members as of 2007 The resulting papers were published in 1928 under the title Theory of continental drift. Wegener himself contributed a paper to this volume. ^[13]

One of the main problems with Wegener's theory was that he believed that the continents "plowed" through the rocks of the ocean basins. Most geologists did not believe that this could be possible. In fact, the biggest objection to Wegener was that he did not have an acceptable theory of the forces that caused the continents to drift. He also ignored counter-arguments and evidence contrary to his theory and seemed too willing to interpret ambiguous evidence as being favorable to his theory. ^[14] For their part, the geologists ignored Wegener's copious body of evidence, allowing their adherence to a theory to override the actual data, when the scientific method would seem to demand the reverse approach. Scientific method refers to bodies of Techniques for investigating phenomena

Plate tectonics, a modern update of the old ideas of Wegener about "plowing" continents, accommodates continental motion through the mechanism of seafloor spreading. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere Seafloor spreading occurs at Mid-ocean ridges where new Oceanic crust is formed through volcanic activity and then gradually moves away from the ridge New rock is created by volcanism at mid-ocean ridges and returned to the Earth's mantle at ocean trenches. Remarkably, in the 1928 AAPG volume, G. A. F. Molengraaf of the Delft Institute (now University) of Technology proposed a recognizable form of seafloor spreading in order to account for the opening of the Atlantic Ocean as well as the East Africa Rift. The Delft University of Technology ( Technische Universiteit Delft in Dutch) in Delft, the Netherlands, is the nation's largest technical The Great Rift Valley is a name given in the late 19th century by English explorer John Walter Gregory to the continuous geographic trough approximately in length that runs Arthur Holmes (an early supporter of Wegener) suggested that the movement of continents was the result of convection currents driven by the heat of the interior of the Earth, rather than the continents floating on the mantle. In the words of Carl Sagan,^[15] it is more like the continents are being carried on a conveyor belt than floating or drifting. Carl Edward Sagan ( November 9 1934 &ndash December 20 1996) was an American Astronomer, astrochemist, author A belt conveyor consists of two or more Pulleys with a continuous loop of material - the conveyor belt - that rotates about them The ideas of Molengraaf and of Holmes led to the theory of plate tectonics, which replaced the theory of continental drift, and became the accepted theory in the 1960s (based on data that started to accumulate in the late 1950s).

However, acceptance was gradual. Nowadays it is universally supported; but even in 1977 a textbook could write the relatively weak: "a poll of geologists now would probably show a substantial majority who favor the idea of drift" and devote a section to a serious consideration of the objections to the theory. ^[16]

Notes and references

• Le Grand, H. Addison-Wesley is a Book publishing imprint of Pearson PLC, best known for computer books E. (1988). Drifting Continents and Shifting Theories. Cambridge University. ISBN 0-521-31105-5.  

External links

• A brief introduction to Plate Tectonics, based on the work of Alfred Wegener.
• Maps of continental drift, from the Precambrian to the future
• Four main evidences of the Continental Drift theory
• Wegener and his proofs