THE FOSSILS CORRELATIONWegener used an Alexander duToit graphic to demonstrate the uncanny match of geology between eastern South America and western Africa.

The Rocks and Mountains Correlation.

We are taught that modern scientists are driven only by reason and facts. It was only early scientists like Galileo who needed to fear the reaction to their radical views. Neither of these beliefs is true. The reaction to Alfred Wegener's Continental Drift Theory demonstrates that new ideas threaten the establishment, regardless of the century.

Alfred Wegener was the scientist who proposed the Continental Drift Theory in the early twentieth century. Simply put, his hypothesis proposed that the continents had once been joined, and over time had drifted apart. The jigsaw fit that the continents make with each other can be seen looking at the map of soil types below (derived from University of Idaho). South America can be dragged and rotated (rotating is tricky by touch) so you can try to see how well it joins with Africa.

Since his ideas challenged scientists in geology, geophysics, zoogeography and paleontology, it demonstrates the reactions of different communities of scientists. These reactions eventually shut down serious discussion of the concept. The geologist Barry Willis summed it up best:

The students' minds would not be befogged. The world had to wait until the 1960's for a wide discussion of the Continental Drift Theory to be restarted.

Why the extreme reaction? Wegener did not even present Continental Drift as a proven theory. He knew he would need more support to convince others. His immediate goal was to have the concept openly discussed. These modest goals did not spare him. His work crossed disciplines. The authorities in the various disciplines attacked him as an amateur that did not fully grasp their own subject. More importantly however, was that even the possibility of Continental Drift was a huge threat to the authorities in each of the disciplines.

Radical viewpoints threaten the authorities in a discipline. Authorities are expert in the current view of their discipline. A radical view could even force experts to start over again. One of Alfred Wegener's critics, the geologist R. Thomas Chamberlain, suggested just that :

He was right.

In spite of all the criticism, Wegener was able to keep Continental Drift part of the discussion until his death. He knew that any argument based simply on the jigsaw fit of the continents could easily be explained away. To strengthen his case he drew from the fields of geology, geography, biology and paleontology. Wegener questioned why coal deposits, commonly associated with tropical climates, would be found near the North Pole and why the plains of Africa would show evidence of glaciation. Wegener also presented examples where fossils of exactly the same prehistoric species were distributed where you would expect them to be if there had been Continental Drift (e.g. one species occurred in western Africa and South America, and another in Antartica, India and central Africa) [_1_] . The graphic below shows the striking distribution of fossils on the different continents.

Wegener used an Alexander duToit graphic to demonstrate the uncanny match of geology between eastern South America and western Africa.

The picture painted of Alfred Wegener's contemporaries might not be fair. One would expect scientists to resist ideas that challenged their life's work. It doesn't explain all of the criticism. There were alternatives. To explain the unusual distribution of fossils in the Southern Hemisphere some scientists proposed there may once have been a network of land bridges between the different continents. To explain the existence of fossils of temperate species being found in arctic regions, the existence of warm water currents was proposed. Modern scientists would look at these explanations as even less credible than those proposed by Wegener, but they did help to preserve the steady state theory.

New theories often have rough edges. Wegener did not have an explanation for how continental drift could have occurred. He proposed two different mechanisms for this drift. One was based on the centrifugal force caused by the rotation of the earth and another a 'tidal argument' based on the tidal attraction of the sun and the moon. These explanations could easily be proven inadequate. They opened Wegener to ridicule because they were orders of magnitude too weak. Wegener really did not believe that he had the explanation for the mechanism, but that this should not stop discussion of a hypothesis. Wegener's contemporaries disagreed. A major conference was held by the American Association of Petroleum Geologists in 1926 that was critical of the theory. Alfred Wegener died a few years later. With his death, the Continental Drift Theory was quietly swept under the rug. The existing theories of continent formation were allowed to survive, with little challenge until the 1960's.

The main problem with Wegener's hypothesis of Continental Drift was the lack of a mechanism. He did not have an explanation for how the continents moved. His attempt to explain it using tides only made things worse. But both Galileo and Darwin had serious flaws in their theories when they were first presented. Galileo had a tidal theory that was more embarassing than Wegener's and Darwin was missing a mechanism for his theory. History treats the three men differently in spite of the fact that their theories arrived with pretty big holes.

Charles Darwin was missing an important mechanism for evolution when he published the Origin of Species in 1859 (see Mendel and Darwin). He argued that with the natural variations that occur in populations, any trait that is beneficial would make that individual more likely to survive and pass on the trait to the next generation. If enough of these selectionsoccured on different beneficial traits you could end up with completely new species. He did not have a mechanism for how the traits could be preserved over the succeeding generations. At the time it was thought that the traits of the parents were blended in the offspring. Unfortunately, blending would dilute any beneficial trait out of a population within a few generations. This is because most of the blending over the next generations would be with individuals that did not have the trait. This gaping hole in the theory didn't stop universities such as Oxford from teaching Evolution as fact shortly after the publication of the Origin of Species. This hole in Darwin's theory was plugged about 50 years later using the work of a Roman Catholic monk, Gregor Mendel. His theory provided an alternative to blending where traits were inherited whole.

Darwin's theory had another problem. His theory proposed a gradual evolution through successive generations. The fossil record of the time contradicted this. There seemed to be an 'explosion' of different life-forms over a relatively short time span in the early Cambrian period ( the Cambrian Explosion). There also didn't seem to be any transitional forms of life preceding these species. New discoveries made the problem worse. Much worse. In 1909, a massive find of 65,000 more specimens of early Cambrian life was discovered in the Burgess Shale in British Columbia, Canada. Many were complex multi-celled animals with no evidence of preceding transitional forms.

Wegener also shares much in common with Galileo. Galileo had his own 'tidal argument' ; one that was even more embarassing than Wegener's. To defend his belief that the sun was the center of the solar system, Galileo argued that the tides were caused by the sun. His argument was based on there only being 1 tide per day and where the tides cycle over the year and not over a month. It didn't take a scientist to realize that the argument was ridiculous.

There were other problems with Galileo's defense of Copernicism. The scientists of Galileo's day did have scientifically valid reasons to doubt a moving earth. A moving earth required that a phenomenon known as stellar parallax (see Copernicism and Stellar Parallax) would be observed . No one in Galileo's day or for two centuries after his death was able to observe this phenomenon. Neither did the current data support Galileo's favoured Copernican Model. Modern statistical analyses don't either [_2_] . Galileo wasn't proposing the Keplerian model that works so well; he was proposing the Copernican Model against the Keplerian and other models. More info on the Galileo Affair can be found at Galileo's Battle for the Heavens and The Galileo Myths.

Why was one theory above quickly accepted, another quickly dismissed, and the other a cause of controversy amongst scientists. Analysis from a strictly scientific basis won't help. All of the theories had strengths and weaknesses. We might have to look beyond the world of ideas to the world of people, events and things.

Darwin, was the ultimate insider in English scientific circles. His grandfather, Erasmus, was an early student of evolution and his half-cousin, Francis Galton, was a noted statistician who was considered the father of eugenics. Being part of the Wedgewood-Darwin clan meant having no worries about money and established connections in the scientific world. When evolution by natural selection was under attack, Darwin could enlist the efforts of a Who's Who of mid-nineteenth century English science. The most famous of the early defenses of Darwinism was not by Darwin himself but by the famous biologist, Thomas Huxley and the social philosopher, Herbert Spencer. Darwin's ideas were adopted by supporters of laissez-faire capitalism. "Survival of the fittest" gave an ethical dimension to the no-holds barred capitalism of the late nineteenth century. Andrew Carnegie, the fabulously rich robber baron, used elements of evolution by natural selection to justify his own ruthless business practices.

Alfred Wegener wasn't an insider. He had to earn all his allies. His few allies (duToit and Holmes) were no match for his many skeptics. His place of birth may have played a role. Anti-German bias was very strong in the 1910's and 1920's in English-speaking countries. This resulted in German-based names for cities, streets, foods and animal breeds being changed to names that were more 'patriotic'. Being German wasn't Wegener's only problem; the arguments he used to support his hypothesis crossed into disciplines that were not his specialty. He was trained as an astronomer and worked as a meterologist. He was considered an outsider for a reason.

The early history of the Copernican model is an example of the effect of outside forces. The publication of Copernicus' de Revolutionibus drew very little criticism from the Catholic countries. The most serious early criticisms came from the Protestant countries in Europe. The Vatican's interest in the publication had begun 10 years earlier, after a series of lectures given to Pope Clement VII on Copernicus's work. Any doubt of the church's support for Copernicus' work ended with the actual publication. The original publication included a copy of the letter from the Vatican urging him to share his work, a dedication to the pope, and a thank you to a bishop who was an important supporter of his work. The involvement of the church may have muted criticism from academics in the Catholic countries of Europe and encouraged criticism in the Protestant countries. The reverse happened after Galileo's trial in 1633. Galileo was tried for not obeying an order from 1616 to not teach the Copernican theory as true but only as a hypothesis. He was placed under house arrest in his villa in the Tuscan hills just outside Florence (see Galileo's Battle for the Heavens).

Science depends on facts. It also depends on reason. But fact and reason alone cannot explain how science works. The examples chosen all had some compelling support and serious shortcomings. Part of the answer may lie in the sociology of groups. Another part lies in simple faith: faith that future scientists will address a theory's shortcomings. Darwin needed an explanation for the Cambrian Explosion and a mechanism for the preservation of traits (see Mendel and Darwin) . Wegener needed a mechanism for Continental Drift. Galileo needed an explanation for the lack of stellar parallax and the poor performance of his model (see Galileo's Battle for the Heavens) . It is not only the community that requires faith. The champions of these new theories require faith in their ideas, even when facts contradict their hypotheses. In each case above, there were facts which when combined with the current assumptions of the time clearly contradicted their hypotheses. None of these scientists let those facts get in the way. Paul Feyerabend, a modern philosopher of science, presents a similar view, where he argues that science is sometimes required to work "against the facts". His key example was how the heliocentric system made less sense than a geocentric system during Galileo's time. One irony missed by discussions of science and religion is how much both depend on faith.

 

Alfred Wegener was the scientist who proposed the Continental Drift Theory in the early twentieth century. Simply put, his hypothesis proposed that the continents had once been joined, and over time had drifted apart. The jigsaw fit that the continents make with each other can be seen looking at the map of soil types below (derived from University of Idaho). South America can be dragged and rotated (rotating is tricky by touch) so you can try to see how well it joins with Africa.

Since his ideas challenged scientists in geology, geophysics, zoogeography and paleontology, it demonstrates the reactions of different communities of scientists. These reactions eventually shut down serious discussion of the concept. The geologist Barry Willis summed it up best:

The students' minds would not be befogged. The world had to wait until the 1960's for a wide discussion of the Continental Drift Theory to be restarted.

Why the extreme reaction? Wegener did not even present Continental Drift as a proven theory. He knew he would need more support to convince others. His immediate goal was to have the concept openly discussed. These modest goals did not spare him. His work crossed disciplines. The authorities in the various disciplines attacked him as an amateur that did not fully grasp their own subject. More importantly however, was that even the possibility of Continental Drift was a huge threat to the authorities in each of the disciplines.

Radical viewpoints threaten the authorities in a discipline. Authorities are expert in the current view of their discipline. A radical view could even force experts to start over again. One of Alfred Wegener's critics, the geologist R. Thomas Chamberlain, suggested just that :

He was right.

In spite of all the criticism, Wegener was able to keep Continental Drift part of the discussion until his death. He knew that any argument based simply on the jigsaw fit of the continents could easily be explained away. To strengthen his case he drew from the fields of geology, geography, biology and paleontology. Wegener questioned why coal deposits, commonly associated with tropical climates, would be found near the North Pole and why the plains of Africa would show evidence of glaciation. Wegener also presented examples where fossils of exactly the same prehistoric species were distributed where you would expect them to be if there had been Continental Drift (e.g. one species occurred in western Africa and South America, and another in Antartica, India and central Africa) [_1_] . The graphic below shows the striking distribution of fossils on the different continents.

Wegener used an Alexander duToit graphic to demonstrate the uncanny match of geology between eastern South America and western Africa.

The picture painted of Alfred Wegener's contemporaries might not be fair. One would expect scientists to resist ideas that challenged their life's work. It doesn't explain all of the criticism. There were alternatives. To explain the unusual distribution of fossils in the Southern Hemisphere some scientists proposed there may once have been a network of land bridges between the different continents. To explain the existence of fossils of temperate species being found in arctic regions, the existence of warm water currents was proposed. Modern scientists would look at these explanations as even less credible than those proposed by Wegener, but they did help to preserve the steady state theory.

New theories often have rough edges. Wegener did not have an explanation for how continental drift could have occurred. He proposed two different mechanisms for this drift. One was based on the centrifugal force caused by the rotation of the earth and another a 'tidal argument' based on the tidal attraction of the sun and the moon. These explanations could easily be proven inadequate. They opened Wegener to ridicule because they were orders of magnitude too weak. Wegener really did not believe that he had the explanation for the mechanism, but that this should not stop discussion of a hypothesis. Wegener's contemporaries disagreed. A major conference was held by the American Association of Petroleum Geologists in 1926 that was critical of the theory. Alfred Wegener died a few years later. With his death, the Continental Drift Theory was quietly swept under the rug. The existing theories of continent formation were allowed to survive, with little challenge until the 1960's.

The main problem with Wegener's hypothesis of Continental Drift was the lack of a mechanism. He did not have an explanation for how the continents moved. His attempt to explain it using tides only made things worse. But both Galileo and Darwin had serious flaws in their theories when they were first presented. Galileo had a tidal theory that was more embarassing than Wegener's and Darwin was missing a mechanism for his theory. History treats the three men differently in spite of the fact that their theories arrived with pretty big holes.

Charles Darwin was missing an important mechanism for evolution when he published the Origin of Species in 1859 (see Mendel and Darwin). He argued that with the natural variations that occur in populations, any trait that is beneficial would make that individual more likely to survive and pass on the trait to the next generation. If enough of these selectionsoccured on different beneficial traits you could end up with completely new species. He did not have a mechanism for how the traits could be preserved over the succeeding generations. At the time it was thought that the traits of the parents were blended in the offspring. Unfortunately, blending would dilute any beneficial trait out of a population within a few generations. This is because most of the blending over the next generations would be with individuals that did not have the trait. This gaping hole in the theory didn't stop universities such as Oxford from teaching Evolution as fact shortly after the publication of the Origin of Species. This hole in Darwin's theory was plugged about 50 years later using the work of a Roman Catholic monk, Gregor Mendel. His theory provided an alternative to blending where traits were inherited whole.

Darwin's theory had another problem. His theory proposed a gradual evolution through successive generations. The fossil record of the time contradicted this. There seemed to be an 'explosion' of different life-forms over a relatively short time span in the early Cambrian period ( the Cambrian Explosion). There also didn't seem to be any transitional forms of life preceding these species. New discoveries made the problem worse. Much worse. In 1909, a massive find of 65,000 more specimens of early Cambrian life was discovered in the Burgess Shale in British Columbia, Canada. Many were complex multi-celled animals with no evidence of preceding transitional forms.

Wegener also shares much in common with Galileo. Galileo had his own 'tidal argument' ; one that was even more embarassing than Wegener's. To defend his belief that the sun was the center of the solar system, Galileo argued that the tides were caused by the sun. His argument was based on there only being 1 tide per day and where the tides cycle over the year and not over a month. It didn't take a scientist to realize that the argument was ridiculous.

There were other problems with Galileo's defense of Copernicism. The scientists of Galileo's day did have scientifically valid reasons to doubt a moving earth. A moving earth required that a phenomenon known as stellar parallax (see Copernicism and Stellar Parallax) would be observed . No one in Galileo's day or for two centuries after his death was able to observe this phenomenon. Neither did the current data support Galileo's favoured Copernican Model. Modern statistical analyses don't either [_2_] . Galileo wasn't proposing the Keplerian model that works so well; he was proposing the Copernican Model against the Keplerian and other models. More info on the Galileo Affair can be found at Galileo's Battle for the Heavens and The Galileo Myths.

Why was one theory above quickly accepted, another quickly dismissed, and the other a cause of controversy amongst scientists. Analysis from a strictly scientific basis won't help. All of the theories had strengths and weaknesses. We might have to look beyond the world of ideas to the world of people, events and things.

Darwin, was the ultimate insider in English scientific circles. His grandfather, Erasmus, was an early student of evolution and his half-cousin, Francis Galton, was a noted statistician who was considered the father of eugenics. Being part of the Wedgewood-Darwin clan meant having no worries about money and established connections in the scientific world. When evolution by natural selection was under attack, Darwin could enlist the efforts of a Who's Who of mid-nineteenth century English science. The most famous of the early defenses of Darwinism was not by Darwin himself but by the famous biologist, Thomas Huxley and the social philosopher, Herbert Spencer. Darwin's ideas were adopted by supporters of laissez-faire capitalism. "Survival of the fittest" gave an ethical dimension to the no-holds barred capitalism of the late nineteenth century. Andrew Carnegie, the fabulously rich robber baron, used elements of evolution by natural selection to justify his own ruthless business practices.

Alfred Wegener wasn't an insider. He had to earn all his allies. His few allies (duToit and Holmes) were no match for his many skeptics. His place of birth may have played a role. Anti-German bias was very strong in the 1910's and 1920's in English-speaking countries. This resulted in German-based names for cities, streets, foods and animal breeds being changed to names that were more 'patriotic'. Being German wasn't Wegener's only problem; the arguments he used to support his hypothesis crossed into disciplines that were not his specialty. He was trained as an astronomer and worked as a meterologist. He was considered an outsider for a reason.

The early history of the Copernican model is an example of the effect of outside forces. The publication of Copernicus' de Revolutionibus drew very little criticism from the Catholic countries. The most serious early criticisms came from the Protestant countries in Europe. The Vatican's interest in the publication had begun 10 years earlier, after a series of lectures given to Pope Clement VII on Copernicus's work. Any doubt of the church's support for Copernicus' work ended with the actual publication. The original publication included a copy of the letter from the Vatican urging him to share his work, a dedication to the pope, and a thank you to a bishop who was an important supporter of his work. The involvement of the church may have muted criticism from academics in the Catholic countries of Europe and encouraged criticism in the Protestant countries. The reverse happened after Galileo's trial in 1633. Galileo was tried for not obeying an order from 1616 to not teach the Copernican theory as true but only as a hypothesis. He was placed under house arrest in his villa in the Tuscan hills just outside Florence (see Galileo's Battle for the Heavens).

Science depends on facts. It also depends on reason. But fact and reason alone cannot explain how science works. The examples chosen all had some compelling support and serious shortcomings. Part of the answer may lie in the sociology of groups. Another part lies in simple faith: faith that future scientists will address a theory's shortcomings. Darwin needed an explanation for the Cambrian Explosion and a mechanism for the preservation of traits (see Mendel and Darwin) . Wegener needed a mechanism for Continental Drift. Galileo needed an explanation for the lack of stellar parallax and the poor performance of his model (see Galileo's Battle for the Heavens) . It is not only the community that requires faith. The champions of these new theories require faith in their ideas, even when facts contradict their hypotheses. In each case above, there were facts which when combined with the current assumptions of the time clearly contradicted their hypotheses. None of these scientists let those facts get in the way. Paul Feyerabend, a modern philosopher of science, presents a similar view, where he argues that science is sometimes required to work "against the facts". His key example was how the heliocentric system made less sense than a geocentric system during Galileo's time. One irony missed by discussions of science and religion is how much both depend on faith.

Searching for evidence to further develop his theory of continental drift, Wegener came across a paleontological paper suggesting that a land bridge had once connected Africa with Brazil. This proposed land bridge was an attempt to explain the well known paleontological observation that the same fossilized plants and animals from the same time period were found in South America and Africa. The same was true for fossils found in Europe and North America, and Madagascar and India. Many of these organisms could not have traveled across the vast oceans that currently exist. Wegener's drift theory seemed more plausible than land bridges connecting all of the continents. But that in itself was not enough to support his idea. Another observation favoring continental drift was the presence of evidence for continental glaciation in the Pennsylvanian period. Striae left by the scraping of glaciers over the land surface indicated that Africa and South America had been close together at the time of this ancient ice age. The same scraping patterns can be found along the coasts of South America and South Africa. 

Wegener's drift hypothesis also provided an alternate explanation for the formation of mountains (orogenesis). The theory being discussed during his time was the "Contraction theory" which suggested that the planet was once a molten ball and in the process of cooling the surface cracked and folded up on itself. The big problem with this idea was that all mountain ranges should be approximately the same age, and this was known not to be true. Wegener's explanation was that as the continents moved, the leading edge of the continent would encounter resistance and thus compress and fold upwards forming mountains near the leading edges of the drifting continents. The Sierra Nevada mountains on the Pacific coast of North America and the Andes on the coast of South America were cited. Wegener also suggested that India drifted northward into the asian continent thus forming the Himalayas.  

Wegener eventually proposed a mechanism for continental drift that focused on his assertion that the rotation of the earth created a centrifugal force towards the equator. He believed that Pangaea originated near the south pole and that the centrifugal force of the planet caused the protocontinent to break apart and the resultant continents to drift towards the equator. He called this the "pole-fleeing force". This idea was quickly rejected by the scientific community primarily because
the actual forces generated by the rotation of the earth were calculated to be insufficient to move continents. Wegener also tried to explain the westward drift of the Americas by invoking the gravitational forces of the sun and the moon, this idea was also quickly rejected. Wegener's inability to provide an adequate explanation of the forces responsible for continental drift and the prevailing belief that the earth was solid and immovable resulted in the scientific dismissal of his theories.

In 1929, about the time Wegener's ideas began to be dismissed, Arthur Holmes elaborated on one of Wegener's many hypotheses; the idea that the mantle undergoes thermal convection. This idea is based on the fact that as a substance is heated its density decreases and rises to the surface until it is cooled and sinks again. This repeated heating and cooling results in a current which may be enough to cause continents to move. Arthur Holmes suggested that this thermal convection was like a conveyor belt and that the upwelling pressure could break apart a continent and then force the broken continent in opposite directions carried by the convection currents. This idea received very little attention at the time.  

Not until the 1960's did Holmes' idea receive any attention. Greater understanding of the ocean floor and the discoveries of features like mid-oceanic ridges, geomagnetic anomalies parallel to the mid-oceanic ridges, and the association of island arcs and oceanic trenches occurring together and near the continental margins, suggested convection might indeed be at work. These discoveries and more led Harry Hess (1962) and R.Dietz (1961) to publish similar hypotheses based on mantle convection currents, now known as "sea floor spreading". This idea was basically the same as that proposed by Holmes over 30 years earlier, but now there was much more evidence to further develop and support the idea. 

Alfred Wegener proposed that the continents were once united into a single supercontinent named Pangaea, meaning all earth in ancient Greek. He suggested that Pangaea broke up long ago and that the continents then moved to their current positions. He called his hypothesis continental drift.

Evidence for Continental Drift

Besides the way the continents fit together, Wegener and his supporters collected a great deal of evidence for the continental drift hypothesis. For one, identical rocks of the same type and age are found on both sides of the Atlantic Ocean. Wegener said the rocks had formed side-by-side and that the land had since moved apart.Mountain ranges with the same rock types, structures, and ages are now on opposite sides of the Atlantic Ocean. The Appalachians of the eastern United States and Canada, for example, are just like mountain ranges in eastern Greenland, Ireland, Great Britain, and Norway. Wegener concluded that they formed as a single mountain range that was separated as the continents drifted.Ancient fossils of the same species of extinct plants and animals are found in rocks of the same age but are on continents that are now widely separated. Wegener proposed that the organisms had lived side by side, but that the lands had moved apart after they were dead and fossilized. He suggested that the organisms would not have been able to travel across the oceans. For example, the fossils of the seed fern Glossopteris were too heavy to be carried so far by wind. The reptile Mesosaurus could only swim in fresh water. was a swimming reptile but could only swim in fresh water. Cynognathus and Lystrosauruswere land reptiles and were unable to swim.Grooves and rock deposits left by ancient glaciers are found today on different continents very close to the equator. This would indicate that the glaciers either formed in the middle of the ocean and/or covered most of the Earth. Today glaciers only form on land and nearer the poles. Wegener thought that the glaciers were centered over the southern land mass close to the South Pole and the continents moved to their present positions later on.Coral reefs and coal-forming swamps are found in tropical and subtropical environments, but ancient coal seams and coral reefs are found in locations where it is much too cold today. Wegener suggested that these creatures were alive in warm climate zones and that the fossils and coal later had drifted to new locations on the continents.Although Wegener’s evidence was sound, most geologists at the time rejected his hypothesis of continental drift. Scientists argued that there was no way to explain how solid continents could plow through solid oceanic crust. Wegener’s idea was nearly forgotten until technological advances presented even more evidence that the continents moved and gave scientists the tools to develop a mechanism for Wegener’s drifting continents.

Fossils of Mesosaurus (one of the first marine reptiles, even older than the dinosaurs) were found in both South America and South Africa. These finds, plus the study of sedimentation and the fossil plant Glossopteris in these southern continents led Alexander duToit, a South African scientist, to bolster the idea of the past existence of a supercontinent in the southern hemisphere, Eduard Suess's Gondwanaland. This lent further support to A. Wegener's Continental Drift Theory
PLATE TECTONICS
The theory of plate tectonics (meaning "plate structure") was developed in the 1960's. This theory explains the movement of the Earth's plates (which has since been documented scientifically) and also explains the cause of earthquakes, volcanoes, oceanic trenches, mountain range formation, and other geologic phenomenon. 

Fossil patterns across continents (Gondwana).

From 1912, Wegener publicly advocated the existence of "continental drift", arguing that all the continents were once joined together in a single landmass and had since drifted apart. He supposed that the mechanisms causing the drift might be the centrifugal force of the Earth's rotation ("Polflucht") or the astronomical precession. Wegener also speculated on sea-floor spreading and the role of the mid-ocean ridges, stating: the Mid-Atlantic Ridge ... zone in which the floor of the Atlantic, as it keeps spreading, is continuously tearing open and making space for fresh, relatively fluid and hot sima [rising] from depth.However, he did not pursue these ideas in his later works.

In 1915, in the first edition of his book, Die Entstehung der Kontinente und Ozeane, written in German (the first English edition was published in 1924 as The Origin of Continents and Oceans, a translation of the 1922 third German edition),Wegener drew together evidence from various fields to advance the theory that there had once been a giant continent which he named "Urkontinent"(German for "primal continent", analogous to the Greek "Pangaea", meaning "All-Lands" or "All-Earth"). Expanded editions during the 1920s presented further evidence. The last German edition, published in 1929, revealed the significant observation that shallower oceans were geologically younger. It was, however, not translated into English until 1962.

We are taught that modern scientists are driven only by reason and facts. It was only early scientists like Galileo who needed to fear the reaction to their radical views. Neither of these beliefs is true. The reaction to Alfred Wegener's Continental Drift Theory demonstrates that new ideas threaten the establishment, regardless of the century.

Alfred Wegener was the scientist who proposed the Continental Drift Theory in the early twentieth century. Simply put, his hypothesis proposed that the continents had once been joined, and over time had drifted apart. The jigsaw fit that the continents make with each other can be seen looking at the map of soil types below (derived fromUniversity of Idaho). South America can be dragged and rotated (rotating is tricky by touch) so you can try to see how well it joins with Africa.

HistoryEdit

This article is about the development of the continental drift hypothesis before 1958. For the contemporary theory, see plate tectonics. For the Russell Banks novel, see Continental Drift (novel). For the fourth film in the Ice Age franchise, see Ice Age: Continental Drift.

The continental drift of the last 250 million years

Antonio Snider-Pellegrini's Illustration of the closed and opened Atlantic Ocean (1858).^[1]

Continental drift is the movement of the Earth's continents relative to each other, thus appearing to "drift" across the ocean bed.^[2]The speculation that continents might have 'drifted' was first put forward by Abraham Ortelius in 1596. The concept was independently and more fully developed by Alfred Wegener in 1912, but his theory was rejected by some for lack of a mechanism, which was supplied later by Arthur Holmes. The idea of continental drift has been subsumed by the theory of plate tectonics, which explains how the continents move.^[3]

HistoryEdit

Further information: Timeline of the development of tectonophysics (before 1954)

Abraham Ortelius (Ortelius 1596),^[4] Theodor Christoph Lilienthal (1756),^[5] Alexander von Humboldt (1801 and 1845),^[5] Antonio Snider-Pellegrini (Snider-Pellegrini 1858), and others had noted earlier that the shapes of continents on opposite sides of the Atlantic Ocean (most notably, Africa and South America) seem to fit together.^[6] W. J. Kious described Ortelius' thoughts in this way:^[7]

In 1889, Alfred Russel Wallace remarked, "It was formerly a very general belief, even amongst geologists, that the great features of the earth's surface, no less than the smaller ones, were subject to continual mutations, and that during the course of known geological time the continents and great oceans had again and again changed places with each other."^[8] He quotes Charles Lyell as saying, "Continents, therefore, although permanent for whole geological epochs, shift their positions entirely in the course of ages."^[9] and claims that the first to throw doubt on this was James Dwight Dana in 1849.

In his Manual of Geology (1863), Dana wrote, "The continents and oceans had their general outline or form defined in earliest time. This has been proved with respect to North America from the position and distribution of the first beds of the Silurian – those of the Potsdam epoch. … and this will probably prove to the case in Primordial time with the other continents also".^[10] Dana was enormously influential in America – his Manual of Mineralogy is still in print in revised form – and the theory became known as Permanence theory.^[11]

This appeared to be confirmed by the exploration of the deep sea beds conducted by the Challenger expedition, 1872-6, which showed that contrary to expectation, land debris brought down by rivers to the ocean is deposited comparatively close to the shore on what is now known as the continental shelf. This suggested that the oceans were a permanent feature of the Earth's surface, and did not change places^{[clarification needed]} with the continents

This article is about the development of the continental drift hypothesis before 1958. For the contemporary theory, see plate tectonics. For the Russell Banks novel, see Continental Drift (novel). For the fourth film in the Ice Age franchise, see Ice Age: Continental Drift.

The continental drift of the last 250 million years

Antonio Snider-Pellegrini's Illustration of the closed and opened Atlantic Ocean (1858).^[1]

Continental drift is the movement of the Earth's continents relative to each other, thus appearing to "drift" across the ocean bed.^[2]The speculation that continents might have 'drifted' was first put forward by Abraham Ortelius in 1596. The concept was independently and more fully developed by Alfred Wegener in 1912, but his theory was rejected by some for lack of a mechanism, which was supplied later by Arthur Holmes. The idea of continental drift has been subsumed by the theory of plate tectonics, which explains how the continents move.^[3]

HistoryEdit

Further information: Timeline of the development of tectonophysics (before 1954)

Abraham Ortelius (Ortelius 1596),^[4] Theodor Christoph Lilienthal (1756),^[5] Alexander von Humboldt (1801 and 1845),^[5] Antonio Snider-Pellegrini (Snider-Pellegrini 1858), and others had noted earlier that the shapes of continents on opposite sides of the Atlantic Ocean (most notably, Africa and South America) seem to fit together.^[6] W. J. Kious described Ortelius' thoughts in this way:^[7]

In 1889, Alfred Russel Wallace remarked, "It was formerly a very general belief, even amongst geologists, that the great features of the earth's surface, no less than the smaller ones, were subject to continual mutations, and that during the course of known geological time the continents and great oceans had again and again changed places with each other."^[8] He quotes Charles Lyell as saying, "Continents, therefore, although permanent for whole geological epochs, shift their positions entirely in the course of ages."^[9] and claims that the first to throw doubt on this was James Dwight Dana in 1849.

In his Manual of Geology (1863), Dana wrote, "The continents and oceans had their general outline or form defined in earliest time. This has been proved with respect to North America from the position and distribution of the first beds of the Silurian – those of the Potsdam epoch. … and this will probably prove to the case in Primordial time with the other continents also".^[10] Dana was enormously influential in America – his Manual of Mineralogy is still in print in revised form – and the theory became known as Permanence theory.^[11]

This appeared to be confirmed by the exploration of the deep sea beds conducted by the Challenger expedition, 1872-6, which showed that contrary to expectation, land debris brought down by rivers to the ocean is deposited comparatively close to the shore on what is now known as the continental shelf. This suggested that the oceans were a permanent feature of the Earth's surface, and did not change places^{[clarification needed]} with the coNtinent

📎 Atlantic Ocean - Wikipedia

Atlantic Ocean - Wikipedia

The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. As one component of the interconnected global ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other definitions describe the Atlantic as extending southward to Antarctica).

wikipedia

ASSIGNMENT (aleza roluna)

ASSIGNMENT (aleza roluna) undefined

Wegener thought all the continents were once joined together in an "Urkontinent" before breaking up and drifting to their current positions. But geologists soundly denounced Wegener's theory of continental drift after he published the details in a 1915 book called "The Origin of Continents and Oceans." Part of the opposition was because Wegener didn't have a good model to explain how the continents moved apart. 

Though most of Wegener's observations about fossils and rocks were correct, he was outlandishly wrong on a couple of key points. For instance, Wegener thought the continents might have plowed through the ocean crust like icebreakers smashing through ice. 

"There's an irony that the key objection to continent drift was that there is no mechanism, and plate tectonics was accepted without a mechanism," to move the continents, said Henry Frankel, an emeritus professor at the University of Missouri-Kansas City and author of the four volume "The Continental Drift Controversy" (Cambridge University Press, 2012).