continental drift hypothesis definition science

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

NOTIFICATIONS

Continental drift.

• + Create new collection

The Earth’s continents have not always been where they are at present. If you look at a map of the world, you might notice what Alfred Wegener noticed – that the continents look as if they could fit together like a big jigsaw puzzle if you were able to move them around. Wegener published his theory in 1915. He tried to explain how the Earth drifted apart, but he was unable to give a scientific explanation. Many years later, though, this theory began to gain popularity, and now we understand more how it is possible that land masses can move.

Continental drift is the concept that the Earth’s continents move relative to each other, with the Earth’s surface being broken into plates.

Nature of science

Although it is reliable and durable, scientific knowledge is neither set in concrete nor perfect. Rather, it is subject to change in the light of new evidence or new interpretation of existing evidence. Because of its tentative nature, we cannot claim ‘absolute truth’ in science. The tentative nature of scientific knowledge also means that laws and theories may change.

What evidence is there that continental drift has occurred?

• The continents can be fitted together rather like a jigsaw.
• Rock records show matching layers, mountain ranges and ancient basement rocks in continents that were once together.
• Glacial striations (scratches) and erratics (rocks moved away by glacial ice from original bedrock) correspond between continents.
• Some distinctive fossils found on the southern continents indicate that they came from one ancient single continent.
• Magnetic records left in the rocks seem to show that the Earth’s poles have changed, but the current thinking is that this is not the case – it is the rocks (plates) that have moved.

How do the plates move?

While the mechanisms are still being discussed, the current thinking is that the upper mantle of the Earth is in a state of convection, with hot material rising under diverging zones (plates moving apart) and cool material sinking in subduction zones (one plate diving and sinking underneath another plate).

At converging plate boundaries, the plates collide and either mountains are formed or one plate is forced down into the mantle (subducted) under another. At transform plate boundaries, one plate slips alongside the other in the opposite direction.

What effect has continental drift had on Antarctica?

• About 300 million years ago (mya ) – There was only one large landmass called Pangaea. At that time, the land that is now Antarctica would have been much closer to the equator.
• 200 mya – Pangaea was separated by the Tethys Ocean. Laurasia was in the north and a southern part of the continent was Gondwana. Laurasia was close to the equator and made up of what is now North America, Europe and Asia. Gondwana consisted of the present day South Africa, South America, India, Australia, New Zealand and Antarctica.
• 180 mya – Gondwana started to break up along the spreading plate boundaries. The climate was warm, and there were animals, trees and no ice sheets, much like New Zealand’s climate today.
• 50 mya – Antarctica moved towards the South Pole, away from Australia and South America and surrounded by the Southern Ocean. Ocean currents and wind could now circle the Earth without being blocked by land masses. These circumpolar winds blocked transfer of heat from the tropics, and heat trapped and carried by ocean currents no longer reached Antarctica. Temperatures cooled, and the East Antarctica ice sheet formed.
• 14 mya – Temperatures were no longer cooling, and the West Antarctica ice sheet formed.

At Antarctica, scientists from GNS are investigating the thickness of Earth’s crust, the way seismic waves move through the crust and are dating rocks to better understand global plate movements and Antarctic’s past environment in relation to global climate change.

Related content

Discover the two violent tectonic events that shaped the continent Zealandia and what makes this submerged continent so different to others.

Activity ideas

Use these activities ideas to help explain tectonic plates:

• New Zealand plate boundary models
• Tectonic sandwiches
• Tectonic jigsaw puzzles

See our newsletters here .

Would you like to take a short survey?

This survey will open in a new tab and you can fill it out after your visit to the site.