used to support the hypothesis of continental drift

Continental Drift: The groundbreaking theory of moving continents

Continental drift theory introduced the idea of moving continents.

• Continental drift theory

Evolving theories

• Continental drift evidence

Additional resources

Continental drift was a revolutionary theory explaining that continents shift position on Earth's surface. The theory was proposed by geophysicist and meteorologist Alfred Wegener in 1912, but was rejected by mainstream science at the time. Scientists confirmed some of Wegener's ideas decades later, which are now part of the widely accepted theory of plate tectonics .

Wegener's continental drift theory introduced the idea of moving continents to geoscience. He proposed that Earth must have once been a single supercontinent before breaking up to form several different continents. This explained how similar rock formations and plant and animal fossils could exist on separated continents. Modern science recognizes this ancient supercontinent called Pangaea did exist before breaking up about 200 million years ago, as Wegener theorized. 

Related: Massive supercontinent will form hundreds of millions of years from now  

Why did scientists reject Wegener's continental drift theory?

Geologists roundly denounced Wegener's continental drift theory 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, something scientists later explained under the umbrella of plate tectonics — the theory that Earth's crust is fractured into plates that move over a rocky inner layer called the mantle . 

"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, Henry Frankel (1944–2019), an emeritus professor at the University of Missouri-Kansas City and author of the four volume " The Continental Drift Controversy " (Cambridge University Press, 2012) previously told Live Science.

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. 

When Wegener proposed continental drift, many geologists were contractionists. They thought Earth's incredible mountains were created because our planet had been cooling and shrinking since its formation, Frankel said. And to account for the identical fossils discovered on continents such as South America and Africa, scientists invoked ancient land bridges, now vanished beneath the sea. 

Researchers argued over the land bridges right up until the plate tectonics theory was developed from the 1950s to the 1970s, Frankel said. For instance, as geophysicists began to realize that continental rocks were too light to sink down to the ocean floor, prominent paleontologists instead wrongly suggested that the similarities between fossils had been overestimated, Frankel said.

Plate tectonics is like a modern update to continental drift. In the 1960s, scientists discovered plate edges through magnetic surveys of the ocean floor and through the seismic listening networks built to monitor nuclear testing, according to Encyclopedia Britannica . Alternating patterns of magnetic anomalies on the ocean floor indicated seafloor spreading , where new plate material is born. Magnetic minerals aligned in ancient rocks on continents also showed that the continents have shifted relative to one another. 

Related: Plate tectonics are 3.6 billion years old, oldest minerals on Earth reveal  

What evidence is there for continental drift?

A map of the continents inspired Wegener's quest to explain Earth's geologic history. He was intrigued by the interlocking fit of Africa's and South America's shorelines. Wegener then assembled an impressive amount of continental drift evidence to show that Earth's continents were once connected in a single supercontinent.

Wegener knew that fossil plants and animals such as mesosaurs , a freshwater reptile found only in South America and Africa during the Permian period, could be found on many continents. He also matched up rock formations on either side of the Atlantic Ocean like puzzle pieces. For example, the Appalachian Mountains (United States) and Caledonian Mountains (Scotland) fit together, as do the Karoo strata in South Africa and Santa Catarina rocks in Brazil.

In fact, plates moving together created the highest mountains in the world, the Himalayans, and the mountains are still growing due to the plates pushing together, even now, according to National Geographic . Despite his incredible continental drift evidence, Wegener never lived to see his theory gain wider acceptance. He died in 1930 at age 50 just two days after his birthday while on a scientific expedition in Greenland , according to the University of Berkeley .

• Learn more about the history of continental drift and plate tectonics from the U.S. Geological Survey . 
• Learn more about Alfred Wegener from the NASA Earth Observatory . 
• Watch this short video on YouTube about plate tectonics and continental drift, from National Geographic . 

This article was updated on Dec. 14, 2021, by Live Science Staff Writer Patrick Pester. Additional reporting by Alina Bradford, Live Science contributor.  

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Scientists may have pinpointed the true origin of the Hope Diamond and other pristine gemstones

Underwater robot in Siberia's Lake Baikal reveals hidden mud volcanoes — and an active fault

Why does striking flint against steel start a fire?

Most Popular

• 2 Claude 3 Opus has stunned AI researchers with its intellect and 'self-awareness' — does this mean it can think for itself?
• 3 Giant, 82-foot lizard fish discovered on UK beach could be largest marine reptile ever found
• 4 Global 'time signals' subtly shifted as the total solar eclipse reshaped Earth's upper atmosphere, new data shows
• 5 Scientists discover once-in-a-billion-year event — 2 lifeforms merging to create a new cell part
• 2 Scientists find one of the oldest stars in the universe in a galaxy right next to ours
• 3 DNA analysis spanning 9 generations of people reveals marriage practices of mysterious warrior culture
• 4 5 catastrophic megathrust earthquakes led to the demise of the pre-Aztec city of Teotihuacan, new study suggests
• 5 Plato's burial place finally revealed after AI deciphers ancient scroll carbonized in Mount Vesuvius eruption

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons
• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

5.2: Wegener and the Continental Drift Hypothesis

• Last updated
• Save as PDF
• Page ID 5380

What is continental drift?

Wegener put together a tremendous amount of evidence that the continents had been joined. He advanced a great idea. But other scientists didn't accept it.

Wegener’s Continental Drift Hypothesis

Wegener put his idea and his evidence together in his book, The Origin of Continents and Oceans . The book was first published in 1915. He included evidence that the continents had been joined. New editions of the book containing additional evidence were published later.

In his book he said that around 300 million years ago, the continents had all been joined. They created a single landmass he called Pangaea, meaning “all earth” in ancient Greek. The super-continent later broke apart. Since then the continents have been moving into their current positions. He called his hypothesis continental drift .

The Problem With The Hypothesis

Wegener had a lot of evidence to support his hypothesis. But he had a problem. The problem was that he could not explain how the continents could move through the oceans. He suggested that continental drift occurred like an icebreaker plows through sea ice ( Figure below). He thought the continents could cut through the ocean floor.

An icebreaking ship.

Other scientists didn't buy his idea. They thought that the continents would be much more deformed than they are.

Wegener believed that Africa and South America had once been joined. He had the evidence. But very few scientists accepted his idea. He needed a mechanism that they would accept.

Alfred Wegener died in 1930 on an expedition on the Greenland icecap. The continental drift hypothesis was put to rest for a few decades. Only when technology could provide even more evidence for continental drift did scientists look into the idea again. Technology also helped scientists to develop a mechanism for how continents could drift.

Further Reading

Magnetic Polarity Evidence for Continental Drift

Bathymetric Evidence for Seafloor Spreading

Magnetic Evidence for Seafloor Spreading

Seafloor Spreading Hypothesis

• Alfred Wegener said that the continents had been joined as a single landmass, which he called Pangaea.
• Wegener thought that Pangaea was together about 300 million years ago.
• Wegener could not develop a mechanism for continents moving through oceanic crust that other scientists would accept.
• Describe the continental drift hypothesis.
• Why did scientists reject Wegener’s idea? What was needed for them to accept it?
• What was Wegener's mechanism for drifting continents?

Explore More

Use the resource below to answer the questions that follow.

• What is uniformitarianism?
• What did Wegener write about in his book?
• What did Wegener think caused continental drift?
• Give specific examples of the response to Wegener's continental drift hypothesis.
• What did scientists learn after the war?

Continental Drift versus Plate Tectonics

A scientific idea that was initially ridiculed paved the way for the theory of plate tectonics, which explains how Earth’s continents move.

Earth Science, Geology, Geography, Physical Geography

Alfred Wegener in Greenland

Plate tectonics is the theory that Earth's land masses are in constant motion. The realization that Earth's land masses move was first proposed by Alfred Wegener, which he called continental drift. He is shown here in Greenland.

Photograph from Pictoral Press

We don’t perceive that the continents we live on are moving. After all, it’s not as if an airplane flight between Europe and Africa takes five hours one year but only three hours the next. But the continents actually are shifting, very slowly, relative to one another. In the early 20th century, a scientific theory called continental drift was proposed about this migration of the continents . That theory was initially ridiculed, but it paved the way for another theory called plate tectonics that scientists have now accepted to explain how Earth’s continents move. The story begins with Alfred Wegener (1880–1930), a German meteorologist and geophysicist who noticed something curious when he looked at a map of the world. Wegener observed that the continents of South America and Africa looked like they would fit together remarkably well—take away the Atlantic Ocean and these two massive landforms would lock neatly together. He also noted that similar fossils were found on continents separated by oceans, additional evidence that perhaps the landforms had once been joined. He hypothesized that all of the modern-day continents had previously been clumped together in a super continent he called Pangaea (from ancient Greek, meaning “all lands” or “all the Earth”). Over millions of years, Wegener suggested, the continents had drifted apart. He did not know what drove this movement, however. Wegener first presented his idea of continental drift in 1912, but it was widely ridiculed and soon, mostly, forgotten. Wegener never lived to see his theory accepted—he died at the age of 50 while on an expedition in Greenland. Only decades later, in the 1960s, did the idea of continental drift resurface. That’s when technologies adapted from warfare made it possible to more thoroughly study Earth. Those advances included seismometers used to monitor ground shaking caused by nuclear testing and magnetometers to detect submarines. With seismometers , researchers discovered that earthquakes tended to occur in specific places rather than equally all over Earth. And scientists studying the seafloor with magnetometers found evidence of surprising magnetic variations near undersea ridges: alternating stripes of rock recorded a flip-flopping of Earth’s magnetic field . Together, these observations were consistent with a new theory proposed by researchers who built on Wegener’s original idea of continental drift —the theory of plate tectonics . According to this theory , Earth’s crust is broken into roughly 20 sections called tectonic plates on which the continents ride. When these plates press together and then move suddenly, energy is released in the form of earthquakes. That is why earthquakes do not occur everywhere on Earth—they’re clustered around the boundaries of tectonic plates. Plate tectonics also explains the stripes of rock on the seafloor with alternating magnetic properties: As buoyant, molten rock rises up from deep within Earth, it emerges from the space between spreading tectonic plates and hardens, creating a ridge. Because some minerals within rocks record the orientation of Earth’s magnetic poles and this orientation flips every 100,000 years or so, rocks near ocean ridges exhibit alternating magnetic stripes. Plate tectonics explains why Earth’s continents are moving; the theory of continental drift did not provide an explanation. Therefore, the theory of plate tectonics is more complete. It has gained widespread acceptance among scientists. This shift from one theory to another is an example of the scientific process: As more observations are made and measurements are collected, scientists revise their theories to be more accurate and consistent with the natural world. By running computer simulations of how Earth’s tectonic plates are moving, researchers can estimate where the planet's continents will likely be in the future. Because tectonic plates move very slowly—only a few centimeters per year, on average—it takes a long time to observe changes. Scientists have found that the planet’s continents will likely again be joined together in about 250 million years. Researchers have dubbed this future continental configuration “ Pangaea Proxima.” One intriguing aspect of Pangaea Proxima is that it will likely contain a new mountain range with some of the world’s highest mountains. That is because as Africa continues to migrate north it will collide with Europe, a collision that will probably create a Himalaya-scale mountain range. However, Christopher Scotese, one of the scientists who developed these simulations , cautions that it is difficult to predict exactly how the continents will be arranged in millions of years. “We don’t really know the future, obviously,” Scotese told NASA. “All we can do is make predictions of how plate motions will continue, what new things might happen, and where it will all end up.”

Articles & Profiles

Media credits.

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Production Managers

Program specialists, last updated.

March 7, 2024

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

The Continental Drift Theory: Revolutionary and Significant

• Plate Tectonics
• Types Of Rocks
• Landforms and Geologic Features
• Weather & Climate

Opposition to Continental Drift Theory

Data supporting continental drift theory.

• Wegener's Search for Scientific Truth

Acceptance of Continental Drift Theory

• MLA, Harvard Graduate School of Design

Continental drift was a revolutionary scientific theory developed in the years 1908-1912 by Alfred Wegener (1880-1930), a German meteorologist, climatologist, and geophysicist, that put forth the hypothesis that the continents had all originally been a part of one enormous landmass or supercontinent about 240 million years ago before breaking apart and drifting to their current locations. Based on the work of previous scientists who had theorized about horizontal movement of the continents over the Earth's surface during different periods of geologic time, and based on his own observations drawing from different fields of science, Wegener postulated that about 200 million years ago, a supercontinent that he called Pangaea (which means "all lands" in Greek) began to break up. Over millions of years the pieces separated, first into two smaller supercontinents, Laurasia and Gondwanaland, during the Jurassic period and then by the end of the Cretaceous period into the continents we know today.

Wegener first presented his ideas in 1912 and then published them in 1915 in his controversial book, "The Origins of Continents and Oceans , " which was received with great skepticism and even hostility. He revised and published subsequent editions of his book in 1920,1922, and 1929. The book (Dover translation of the 1929 fourth German edition) is still available today on Amazon and elsewhere.

Wegener's theory, although not completely correct, and by his own admission, incomplete, sought to explain why similar species of animals and plants, fossil remains, and rock formations exist on disparate lands separated by great distances of sea. It was an important and influential step that ultimately led to the development of the theory of plate tectonics , which is how scientists understand the structure, history, and dynamics of the Earth’s crust.

There was much opposition to Wegener's theory for several reasons. For one, he was not an expert in the field of science in which he was making a hypothesis , and for another, his radical theory threatened conventional and accepted ideas of the time. Furthermore, because he was making observations that were multidisciplinary, there were more scientists to find fault with them.

There were also alternative theories to counter Wegener’s continental drift theory. A commonly held theory to explain the presence of fossils on disparate lands was that there was once a network of land bridges connecting the continents that had sunk into the sea as part of a general cooling and contraction of the earth. Wegener, however, refuted this theory maintaining that continents were made of a less dense rock than that of the deep-sea floor and so would have risen to the surface again once the force weighing them down had been lifted. Since this had not occurred, according to Wegener, the only logical alternative was that the continents themselves had been joined and had since drifted apart.

Another theory was that the fossils of temperate species found in the arctic regions were carried there by warm water currents. Scientists debunked these theories, but at the time they helped stall Wegener’s theory from gaining acceptance.

In addition, many of the geologists who were Wegener's contemporaries were contractionists. They believed that the Earth was in the process of cooling and shrinking, an idea they used to explain the formation of mountains, much like wrinkles on a prune. Wegener, though, pointed out that if this were true, mountains would be scattered evenly all over the Earth's surface rather than lined up in narrow bands, usually at the edge of a continent. He also offered a more plausible explanation for mountain ranges. He said they formed when the edge of a drifting continent crumpled and folded — as when India hit Asia and formed the Himalayas.

One of the biggest flaws of Wegener’s continental drift theory was that he did not have a viable explanation for how continental drift could have occurred. He proposed two different mechanisms, but each was weak and could be disproven. One was based on the centrifugal force caused by the rotation of the Earth, and the other was based on the tidal attraction of the sun and the moon.

Though much of what Wegener theorized was correct, the few things that were wrong were held against him and prevented him from seeing his theory accepted by the scientific community during his lifetime. However, what he got right paved the way for plate tectonics theory.

Fossil remains of similar organisms on widely disparate continents support the theories of continental drift and plate tectonics. Similar fossil remains, such as those of the Triassic land reptile Lystrosaurus and the fossil plant Glossopteris , exist in South America, Africa, India, Antarctica, and Australia, which were the continents comprising Gondwanaland, one of the supercontinents that broke off from Pangaea about 200 million years ago. Another fossil type, that of the ancient reptile Mesosaurus , is only found in southern Africa and South America.  Mesosaurus was a freshwater reptile only one meter long that could not have swum the Atlantic Ocean, indicating that there was once a contiguous landmass that provided a habitat for it of freshwater lakes and rivers.

Wegener found evidence of tropical plant fossils and coal deposits in the frigid arctic near the North Pole, as well as evidence of glaciation on the plains of Africa, suggesting a different configuration and placement of the continents than their present one.

Wegener observed that the continents and their rock strata fit together like pieces of a jigsaw puzzle, particularly the east coast of South America and the west coast of Africa, specifically the Karoo strata in South Africa and Santa Catarina rocks in Brazil. South America and Africa were not the only continents with similar geology , though. Wegener discovered that the Appalachian Mountains of the eastern United States, for instance, were geologically related to the Caledonian Mountains of Scotland. 

Wegener's Search for Scientific Truth

According to Wegener, scientists still did not appear to understand sufficiently that all earth sciences must contribute evidence toward unveiling the state of our planet in earlier times, and that the truth of the matter could only be reached by combing all this evidence. Only by combing the information furnished by all the earth sciences would there be hope to determine "truth," that is to say, to find the picture that sets out all the known facts in the best arrangement and that therefore has the highest degree of probability. Further, Wegener believed that scientists always need to be prepared for a possibility that a new discovery, no matter what science furnishes it, may modify the conclusions we draw.

Wegener had faith in his theory and persisted in using an interdisciplinary approach, drawing on the fields of geology, geography, biology, and paleontology, believing that to be the way to strengthen his case and to keep up the discussion about his theory. His book, "The Origins of Continents and Oceans , " also helped when it was published in multiple languages in 1922, which brought it worldwide and ongoing attention within the scientific community. When Wegener gained new information, he added to or revised his theory, and published new editions. He kept the discussion of the plausibility of the continental drift theory going until his untimely death in 1930 during a meteorologic expedition in Greenland.

The story of the continental drift theory and its contribution to scientific truth is a fascinating example of how the scientific process works and how scientific theory evolves. Science is based on hypothesis, theory, testing, and interpretation of data, but the interpretation can be skewed by the perspective of the scientist and his or her own field of specialty, or denial of facts altogether. As with any new theory or discovery, there are those who will resist it and those who embrace it. But through Wegener’s persistence, perseverance, and open-mindedness to the contributions of others, the theory of continental drift evolved into the widely accepted theory today of plate tectonics. With any great discovery it is through the sifting of data and facts contributed by multiple scientific sources, and ongoing refinements of the theory, that scientific truth emerges.

When Wegener died, discussion of continental drift died with him for a while. It was resurrected, however, with the study of seismology and further exploration of the ocean floors in the 1950s and 1960s that showed mid-ocean ridges, evidence in the seafloor of the Earth's changing magnetic field, and proof of seafloor spreading and mantle convection, leading to the theory of plate tectonics. This was the mechanism that was missing in Wegener's original theory of continental drift. By the late 1960s, plate tectonics was commonly accepted by geologists as accurate.

But the discovery of seafloor spreading disproved a part of Wegener's theory, because it wasn't just the continents that were moving through static oceans, as he had originally thought, but rather entire tectonic plates, consisting of the continents, ocean floors, and parts of the upper mantle. In a process similar to that of a conveyor belt, hot rock rises from the mid-ocean ridges and then sinks down as it cools and becomes denser, creating convection currents that cause movement of the tectonic plates.

The theories of continental drift and plate tectonics are the foundation of modern geology. Scientists believe that there were several supercontinents like Pangaea that formed and broke apart over the course of Earth's 4.5-billion year lifespan. Scientists also now recognize that Earth is constantly changing and that even today, the continents are still moving and changing. For example, the Himalayas, formed by the collision of the Indian plate and the Eurasian plate is still growing, because plate tectonics is still pushing the Indian plate into the Eurasian plate. We may even be heading toward the creation of another supercontinent in 75-80 million years due to the continued movement of tectonic plates.

But scientists are also realizing that plate tectonics does not work merely as a mechanical process but as a complex feedback system, with even things such as climate affecting the movement of the plates, creating yet another quiet revolution in the theory of plate tectonics variable in our understanding of our complex planet.

• Learn About the History and Principles of Plate Tectonics
• Biography of Alfred Wegener, German Scientist
• History of the Supercontinent Pangea
• Alfred Wegener's Pangaea Hypothesis
• All About Supercontinents
• Divergent Plate Boundaries
• Map of Tectonic Plates and Their Boundaries
• The Most Influential Geologists of All Time
• The Age of the Ocean Floor
• Measuring Plate Motion in Plate Tectonics
• Orogeny: How Mountains Form Through Plate Tectonics
• Tectonic Plates' Effect on Evolution
• What Is an Ophiolite?
• What Happens at Transform Boundaries?
• Zealandia: The Drowned Continent of the South
• Everything You Need to Know About the Lithosphere

Alfred Wegener: Building a Case for Continental Drift

Continental Drift

The Theory of Continental Drift is defined as the movement of the Earth’s continents relative to each other, thereby appearing to drift together across the oceanic bed. Although Alfred Wegener was able to produce a viable hypothesis with evidence and specifically state the theory, it should be noted there were previous geologists and scientists who thought similar to Wegener. For example, between 1889 and 1909 Roberto Mantovani speculated that all continents had once been conjoined in a “supercontinent,” and even developed an expanding Earth hypothesis.

A depiction of the continents joined together as the “supercontinent,” Pangea, and the path that led them to the positions they reside in today.

Alfred Wegener’s curiosity toward the possibility of continental drift came in 1910 after he noticed how Earth’s continents resembled pieces of a jigsaw puzzle. For example, he noted how South America coast correctly lined up with the coast of Northwest Africa. It wasn’t until 1911, when Wegener came across several scientific documents listing fossils of identical plants and animals found on opposite sides of the Atlantic that his passion for the subject truly showed. Reflecting on this monumental moment in his life, he wrote, “A conviction of the fundamental soundness of the idea took root in my mind.” Alfred Wegener knew massive amounts of evidence needed to be collected in order to justify such a fantastic idea—because with no practical driving force behind it the theory loses most of its credit. In order to maximize evidence for his theory and overlook the absence of a mechanism, he decided to draw from a variety of scientific fields including geology, geography, biology, and paleontology.

10 Books to Understand Climate Change

Deciphering brain coding: the last frontier, openmind books, scientific anniversaries, why we know the lunar missions were real, featured author, latest book, wegener and his theory of continental drift that broke with geologists.

If there were a “geographical forecast”, analogous to the predictions of meteorologists, it would show how over the next 100 million years the Atlantic Ocean will continue to expand, until it is much larger than the Pacific. And also how Africa will merge with Europe, with the Mediterranean disappearing and a mountain range emerging in its place to compete with the Himalayas—although Everest and its neighbouring mountains will still continue to rise. If this sounds shocking today, you should put yourself in the shoes of geologists back in 1912, who were much more troubled when a 32-year-old German meteorologist, Alfred Wegener, launched his theory of continental drift. Thanks to his hypothesis, any child today knows that the continents are slowly moving and were joined together at the time when the dinosaurs appeared.

Credit : Tech Insider

Ever since the appearance of the first world maps, many people had noticed how well Brazil fits snugly under the belly of Africa. Alfred Wegener (1 November 1880 – November 1930) looked for other connections. He found research on identical fossils on the coasts of Africa and South America, something for which geologists, convinced that the world map was immutable, had offered a more implausible explanation: land bridges that had vanished after permitting animals and plants to travel from one continent to another.

Pangea, the supercontinent

But no matter how many bridges were dreamt up, the most renowned geologists were unable to explain why in Africa there are marking of glaciers or why near the North Pole there are remains of tropical vegetation in the form of coal. For Wegener this was only possible if the current continents were once concentrated around the equator forming a supercontinent, which broke apart some 200 million years ago and which he called Pangaea. Nobody had thought of relating all these facts, but Wegener saw in them the evidence of continental drift, thanks to his interest in different sciences.

With his multidisciplinary calling, Wegener had started out as an astronomer, being correct when he stated that craters on the Moon are the work of meteorites and not of volcanoes; later, he combined meteorological studies in Greenland with his geological theories, and did not have a steady job until after the age of 40, when an Austrian University created a post for him. He was a difficult scientist to pigeonhole. And for geologists he was an outsider who dared to question the foundations of their science, so most of them rejected his ideas with the backing of figures like Einstein, who wrote the prologue to a book that ridiculed Wegener.

A puzzle of tectonic plates

It is also true that he made some blunders, calculating that Greenland was approaching North America at a rate of 1.6 km each year, and saying that the continents were moving over the seabed but without explaining why. That was like saying that a plough can move on its own and leave no furrows. Tests were done, but with the most reliable instruments of the time no movement of the continents was detected. The 1964 edition of the Encyclopedia Britannica still did not believe Wegener, but that year many geologists began siding with him, in view of new evidence. The idea took hold that the Earth’s crust is a jigsaw puzzle of plates, which move as whole pieces and not just the highest parts, the continents. This new theory— plate tectonics —also explained that earthquakes and tsunamis occur when two plates rub against one another, and that when they collide head-on, large mountain ranges are formed.

In addition, thanks to geolocation satellites, we are now able to detect that Europe and North America are moving apart, although at the same speed that a fingernail grows: two metres in a lifetime. Today we have all learned at school—or even before, in cartoons—the theory of continental drift. But Wegener died in 1930, long before his success was recognised. During an expedition in Greenland, he left the camp for supplies and was found frozen months later. He was buried there and is still there, although he is now about two metres further away from his birthplace in Berlin.

Francisco Doménech @fucolin

Related publications.

• Zealandia: What is the Interest of Having a New Continent?
• Zealandia and the Mystery of the Origin of Flowers
• Great Adventurers of Science

More about Science

Environment, leading figures, mathematics, scientific insights, more publications about ventana al conocimiento (knowledge window), comments on this publication.

Morbi facilisis elit non mi lacinia lacinia. Nunc eleifend aliquet ipsum, nec blandit augue tincidunt nec. Donec scelerisque feugiat lectus nec congue. Quisque tristique tortor vitae turpis euismod, vitae aliquam dolor pretium. Donec luctus posuere ex sit amet scelerisque. Etiam sed neque magna. Mauris non scelerisque lectus. Ut rutrum ex porta, tristique mi vitae, volutpat urna.

Sed in semper tellus, eu efficitur ante. Quisque felis orci, fermentum quis arcu nec, elementum malesuada magna. Nulla vitae finibus ipsum. Aenean vel sapien a magna faucibus tristique ac et ligula. Sed auctor orci metus, vitae egestas libero lacinia quis. Nulla lacus sapien, efficitur mollis nisi tempor, gravida tincidunt sapien. In massa dui, varius vitae iaculis a, dignissim non felis. Ut sagittis pulvinar nisi, at tincidunt metus venenatis a. Ut aliquam scelerisque interdum. Mauris iaculis purus in nulla consequat, sed fermentum sapien condimentum. Aliquam rutrum erat lectus, nec placerat nisl mollis id. Lorem ipsum dolor sit amet, consectetur adipiscing elit.

Nam nisl nisi, efficitur et sem in, molestie vulputate libero. Quisque quis mattis lorem. Nunc quis convallis diam, id tincidunt risus. Donec nisl odio, convallis vel porttitor sit amet, lobortis a ante. Cras dapibus porta nulla, at laoreet quam euismod vitae. Fusce sollicitudin massa magna, eu dignissim magna cursus id. Quisque vel nisl tempus, lobortis nisl a, ornare lacus. Donec ac interdum massa. Curabitur id diam luctus, mollis augue vel, interdum risus. Nam vitae tortor erat. Proin quis tincidunt lorem.

Herd Immunity, a Double-Edged Idea Against the Pandemic

Do you want to stay up to date with our new publications.

Receive the OpenMind newsletter with all the latest contents published on our website

OpenMind Books

• The Search for Alternatives to Fossil Fuels
• View all books

About OpenMind

Connect with us.

• Keep up to date with our newsletter

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons
• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

15.1: Plate Tectonics and Continental Drift

• Last updated
• Save as PDF
• Page ID 16486

• Michael E. Ritter
• University of Wisconsin-Stevens Point via The Physical Environment

Introduction

The surface of the lithosphere is fractured into a number of tectonic plates (also known as lithospheric or crustal plates) which are in constant motion. As these plates move and collide, the lithosphere buckles, warps, and is torn apart. When this occurs, the Earth's surface shakes with great force, like that which accompanies earthquakes. Volcanoes are common along many plate boundaries as well.

Plate Tectonics

Look at a map of the Earth like that in Figure \(\PageIndex{3}\). Carefully examine the east coast of South America and then let your eyes drift to the west coast of Africa. It looks like you could "fit" South America up against Africa like a puzzle. The same can be said for the fit between North America, Africa, and Europe (Figure \(\PageIndex{4}\))

When we slide the continents together, some over lap between the land masses occurs. This is possibly due to the creation of exotic terrain , new land that has been formed somewhere else and moved to its present location. This remarkable correspondence provides circumstantial evidence for the theory of continental drift.

Looking for the evidence

If the continents were in one piece at some time in the past, we should find similar fossils and rocks on both continents which is precisely what Wegener discovered. By studying the geologic record, the fossil record, and climatic record, he found remarkable similarities between Africa and South America.

Fossils of the same species of plants and animals were found in similar geologic formations in different parts of the world, most notably South America, Africa, and India. For example, fossils of the Glossopteris, an ancient fern, are found in South America, Africa, Antarctica, India, and Australia. It was hypothesized that such a distribution could only come about if the continents were all part of the one super-continent.

Examining the stratigraphy (vertical sequences) of the rock record, Wegener could point to further evidence for Pangea and continental drift. Wegener noted that the rock sequences in South America, Africa, India, and Australia are very similar. Wegener showed that the same three bottoms layers occurred on each of the continents. The bottom layer, called tillite, was thought to be of glacial origin. The middle layer composed of coal beds, shale and sandstone contained Glossopteris fossils, as did the bottom tillite layer. The top most and youngest layer is lava flows. Such a strong similarity in the rock record of these localities, now separated by great geographic distance, lent credence to Wegener's notion of continental drift.

The occurrence of glacial features (Figure \(\PageIndex{7}\)) in the geologic record of South America, Africa, India ,and Australia provides further evidence for the notion of continental drift. Glaciers affected all or part of these continents at the same time in Earth history.

Video : Pangea (Courtesy Khan Academy)

The Mobile Crust

Wegener's ideas were not readily accepted during his day because he did not offer a plausible mechanism for the movement of the continents. Wegener suggested it was the spin of the Earth that caused plates to "plow" their way through the mantle beneath (Figure \(\PageIndex{9}\)).

In the late 1950's and early 1960's oceanographic research was opening the final frontier on Earth, the mysteries of the ocean floor. During the 1950's seismologists showed that earthquake activity was concentrated along the longest continuous mountain system on Earth, the mid-ocean ridge. Known for over a century, the mid-ocean ridge system in the Atlantic Ocean rises some 6,500 feet above the surrounding ocean floor and extends for more that 37,500 miles (60,000 km) in all the world's oceans. At the crest of the ridge system lies a trough or rift. These rifts are about 20 miles wide (30 km) and 6,500 feet (2,900 m) deep and are a site where lava is expelled on to the ocean floor. The youngest material is found near the ridge with rocks of increasing age further away. It appears that the mid-ocean ridge is the site of sea floor spreading leading to plate movement. The key to sea floor spreading was found in the magnetic properties of rock lying on the sea floor.

Geoscientists found that as new material is extruded from the mid-ocean ridge onto the ocean floor, the polarity of the rocks is frozen in time. Dragging a magnetometer across the ridge, they noticed that the polarity recorded a series of "flips" when the polarity of the rocks reversed. Parallel stripes of magnetic reversals on either side of the ridge was supporting evidence for sea floor spreading. ( See animation of magnetic stripe formation - caution large file) ( For more details see: North Cascades Geology - Sea Floor spreading" and Magnetic Stripes and isotope clocks (USGS). These ideas set the stage for further research that has given us a plausible explanation for the movement of the crust and the drifting of continents first proposed by Wegener.

Modern Theory of Plate Movement and Continental Drift

The movement of lithospheric plates referred to as continental drift , is believed to be caused by the radioactive decay of elements in the core and mantle that produces heat. The heat in turn creates convection currents in the mantle which "drive" the plates along their path of movement. When plates collide, heavier, more dense plates dive beneath lighter, less dense crustal plates along subduction zones . As the heavier plate moves downward into the mantle, the increase in temperature and pressure drive water and other volatile fluids ("dewatering") from the oceanic crust. At a depth of 100 kilometers (60 miles), the water-rich fluids decrease the melting point of mantle rock causing it to melt. The magma that slowly moves upwards and may be extruded onto the surface as lava (Figure \(\PageIndex{13}\)). Some plates slip past one another, creating earthquakes, (Figure \(\PageIndex{13}\)) like what happens along the San Andreas fault in California. In many places the crust is separating and moving away in opposite directions, or diverging as happened to create the Great Rift Valley of Africa .

Though many earthquakes seemingly occur along plate boundaries, they can occur far away from the edges of plates too. One of the most well-known seismic regions is the New Madrid Seismic Zone located in the Mississippi Valley of the central United States. Investigate the New Madrid Seismic Zone by reading The Mississippi Valley - "Whole Lotta Shakin' Goin' On" . Then return here to continue.

Video : Plate tectonics: Evidence of plate movement (Courtesy of Khan Academy)

Module 5: Plate Tectonics

Reading: continental drift, the continental drift idea.

Figure 1. The continents fit together like pieces of a puzzle. This is how they looked 250 million years ago.

Find a map of the continents and cut each one out. Better yet, use a map where the edges of the continents show the continental shelf. That’s the true size and shape of a continent. Can you fit the pieces together? The easiest link is between the eastern Americas and western Africa and Europe, but the rest can fit together too (Figure 1).

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.

• 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.

Figure 2. The similarities between the Appalachian and the eastern Greenland mountain ranges are evidences for the continental drift hypothesis.

• Fossils of the seed fern Glossopteris were too heavy to be carried so far by wind.
• Mesosaurus was a swimming reptile but could only swim in fresh water.

Figure 3. Wegener used fossil evidence to support his continental drift hypothesis. The fossils of these organisms are found on lands that are now far apart.

• 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.

Take a look at this animation showing that Earth’s climate belts remain in roughly the same position while the continents move and this animation showing how the continents split up.

Although Wegener’s evidence was sound, most geologists at the time rejected his hypothesis of continental drift. Why do you think they did not accept 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.

Magnetic Polarity Evidence

Figure 4. Earth’s magnetic field is like a magnet with its north pole near the geographic North Pole and the south pole near the geographic South Pole.

Puzzling new evidence came in the 1950s from studies on the Earth’s magnetic history (figure 4). Scientists used magnetometers , devices capable of measuring the magnetic field intensity, to look at the magnetic properties of rocks in many locations.

Magnetite crystals are like tiny magnets that point to the north magnetic pole as they crystallize from magma. The crystals record both the direction and strength of the magnetic field at the time. The direction is known as the field’s magnetic polarity.

Magnetic Polarity on the Same Continent with Rocks of Different Ages

Geologists noted important things about the magnetic polarity of different aged rocks on the same continent:

Figure 5. Earth’s current north magnetic pole is in northern Canada.

• Older rocks that are the same age and are located on the same continent point to the same location, but that location is not the current north magnetic pole.
• Older rock that are of different ages do not point to the same locations or to the current magnetic north pole.

Figure 6. The location of the north magnetic north pole 80 million years before present (mybp), then 60, 40, 20, and now.

In other words, although the magnetite crystals were pointing to the magnetic north pole, the location of the pole seemed to wander. Scientists were amazed to find that the north magnetic pole changed location through time (figure 6).

There are three possible explanations for this:

• The continents remained fixed and the north magnetic pole moved.
• The north magnetic pole stood still and the continents moved.
• Both the continents and the north pole moved.

Magnetic Polarity on Different Continents with Rocks of the Same Age

Geologists noted that for rocks of the same age but on different continents, the little magnets pointed to different magnetic north poles.

• 400-million-year-old magnetite in Europe pointed to a different north magnetic pole than the same-aged magnetite in North America.
• 250 million years ago, the north poles were also different for the two continents.

The scientists looked again at the three possible explanations. Only one can be correct. If the continents had remained fixed while the north magnetic pole moved, there must have been two separate north poles. Since there is only one north pole today, the only reasonable explanation is that the north magnetic pole has remained fixed but that the continents have moved.

To test this, geologists fitted the continents together as Wegener had done. It worked! There has only been one magnetic north pole and the continents have drifted (figure 7). They named the phenomenon of the magnetic pole that seemed to move but actually did not apparent polar wander.

Figure 7. On the left: The apparent north pole for Europe and North America if the continents were always in their current locations. The two paths merge into one if the continents are allowed to drift.

This evidence for continental drift gave geologists renewed interest in understanding how continents could move about on the planet’s surface.

Lesson Summary

• In the early part of the 20th century, scientists began to put together evidence that the continents could move around on Earth’s surface.
• The evidence for continental drift included the fit of the continents; the distribution of ancient fossils, rocks, and mountain ranges; and the locations of ancient climatic zones.
• Although the evidence for continental drift was extremely strong, scientists rejected the idea because no mechanism for how solid continents could move around on the solid earth was developed.
• The discovery of apparent polar wander renewed scientists interest in continental drift.

Contribute!

Improve this page Learn More

• 6.2: Continental Drift. Provided by : CK-12. Located at : http://www.ck12.org/book/CK-12-Earth-Science-For-High-School/section/6.2/ . License : CC BY-NC: Attribution-NonCommercial