Alfred Wegener, a German meteorologist, introduced his hypothesis of Continental Drift in 1912, suggesting that continents had moved across the Earth’s surface over geologic time. He proposed that all landmasses were once joined in a single supercontinent, Pangaea, which began to break apart approximately 200 million years ago. Despite his compelling evidence, the scientific community largely dismissed his theory for several decades. The rejection stemmed not from a lack of supporting data, but from a profound disagreement with the physical mechanism he proposed. The belief in a static, rigid Earth made the idea of shifting continents seem physically impossible.
Wegener’s Supporting Evidence
Wegener gathered data from multiple scientific disciplines to build a powerful case for his hypothesis. The most visually striking evidence was the “jigsaw puzzle” fit of the continents, particularly the complementary coastlines of South America and Africa. He used the true edges of the continental shelves rather than the visible shorelines, providing a much more accurate fit than previous attempts.
He also noted striking correlations in matching rock types and geologic structures across ocean basins. For instance, the Appalachian Mountains in North America shared the same rock type, structure, and age as mountain ranges in eastern Greenland, Great Britain, and Norway. This suggested they were once part of a single, continuous mountain belt that had been torn apart.
Fossil evidence indicated that ancient life forms had inhabited now-separated landmasses. Fossils of the freshwater reptile Mesosaurus were found in both South America and Africa, a creature unable to cross the saltwater Atlantic. Similarly, the seed fern Glossopteris was found across five southern continents, suggesting these landmasses were once connected and shared a unified climate zone.
Finally, paleoclimatic evidence showed anomalies that only continental movement could explain. Ancient glacial deposits (tillites) were found in tropical regions like India and Africa. Conversely, coal deposits, which form in warm swamps, were discovered in the Arctic Circle. Wegener argued that continents must have drifted from polar to equatorial latitudes, or vice versa, to account for these extreme shifts in climate evidence.
The Flaw in the Proposed Mechanism
The primary reason for the rejection of Continental Drift was Wegener’s inability to identify a physically plausible force capable of moving massive continents. The scientific consensus held that the Earth’s mantle was too rigid and solid to allow for horizontal movement of landmasses. The prevailing model viewed continents as permanent and fixed features of the planet’s surface.
Wegener proposed two possible driving forces, both easily disproven by geophysicists. The first was a “pole-fleeing force,” or Polflucht, suggesting that centrifugal force from the Earth’s rotation pulled continents toward the equator. The second mechanism was tidal forces, suggesting that the gravitational pull of the Sun and Moon could drag the continents across the oceanic crust.
Physicists demonstrated that these forces were far too weak to overcome the friction and strength of the Earth’s crust. Calculations showed that the necessary forces would be so immense they would cause the Earth’s rotation to slow down significantly, which was not observed. Furthermore, Wegener envisioned continents as less-dense rock “plowing” through the denser oceanic crust, an idea that was physically impossible without the continents being destroyed. The lack of a verifiable mechanism left the theory as an unsupported collection of observations.
Alternative Explanations and Scientific Opposition
The scientific community favored the Contracting Earth Theory, which proposed that the planet was cooling and shrinking, causing the crust to wrinkle and form mountains through vertical movements. This model explained mountain building without requiring horizontal continental movement. To account for the fossil and geological matches Wegener cited, geologists proposed land bridges, submerged continental connections that allowed ancient organisms to migrate before sinking beneath the ocean.
Wegener’s status as a meteorologist, rather than a formally trained geologist, also contributed to the skepticism. His “outsider” status made it easier for established geologists to dismiss his ideas and critique his data as “cherry-picked” or misinterpreted. Critics argued that the distribution of ancient life forms could be explained by them being more widespread or by surviving short oceanic crossings.
The permanence of ocean basins and continents was a deeply entrenched paradigm that Wegener’s theory threatened to overturn. Many geologists felt the evidence for movement was not compelling enough to abandon the established, fixed-Earth model. Critiques focused heavily on the imprecision of Wegener’s early data and his speculative mechanisms, leading to the theory’s rejection during major scientific conferences in the 1920s.
Post-Rejection Validation of the Concept
Decades after Wegener’s death in 1930, new technological advancements and research validated his core concept of moving continents. Beginning in the 1950s and 1960s, extensive mapping of the ocean floor revealed the continuous mid-ocean ridge system. This led to the discovery of seafloor spreading, where new oceanic crust is constantly created at these ridges and moves outward.
Further evidence came from paleomagnetism, which documented magnetic stripes of alternating polarity preserved in the oceanic crust parallel to the ridges. This pattern confirmed the mobility of the ocean floor and the continents resting on it. These discoveries provided the missing mechanism Wegener lacked: mantle convection, a process where heat from the Earth’s interior drives slow currents in the mantle, carrying the surface plates along. This modern understanding was formalized as the theory of Plate Tectonics, which incorporated Wegener’s concept and finally granted it scientific acceptance.