Continental drift is the idea that Earth's continents have not always been in their current positions — they have slowly moved over millions of years. In 1912, Alfred Wegener proposed that all the continents were once joined in a single supercontinent called Pangaea, which broke apart and drifted to their present locations. His evidence included the jigsaw-puzzle fit of coastlines (especially South America and Africa), matching fossils on continents now separated by oceans, similar rock formations on different continents, and evidence of past climates in unexpected locations (glacial scratches in tropical Africa). Wegener's idea was rejected at first because he could not explain what force moved the continents, but it was later confirmed by the theory of plate tectonics.
Cut out continent shapes from a map and let students physically fit them together like puzzle pieces, especially South America and Africa. Show maps of fossil distributions — the same land-dwelling reptile (Mesosaurus) found on both South America and Africa, which could not have swum across the Atlantic. Discuss what kind of evidence would convince skeptics. The historical rejection and eventual acceptance of Wegener's idea is also a valuable lesson about how science works.
Look at a world map. Notice how the east coast of South America and the west coast of Africa look like they could fit together, like two pieces of a jigsaw puzzle. You are not imagining it. In 1912, a German scientist named Alfred Wegener proposed a radical idea: these continents were once joined and have slowly drifted apart over millions of years. He called the original supercontinent Pangaea, meaning "all lands."
Wegener gathered four types of evidence. First, the coastline fit — not just South America and Africa, but when you reassemble all the continents, they fit together remarkably well. Second, fossils: identical fossils of Mesosaurus, a small freshwater reptile, were found in both Brazil and South Africa. This animal could not have swum across thousands of kilometers of open ocean, so the simplest explanation is that the two continents were once connected. Third, matching rocks: mountain chains and distinctive rock formations on one continent line up perfectly with formations on another when the continents are pushed back together. Fourth, climate evidence: glacial scratches and deposits were found in places like India and Africa that are now tropical, suggesting those continents were once near the South Pole.
Despite all this evidence, most scientists rejected Wegener's idea. The problem was the mechanism — Wegener could show that continents had moved but could not explain what force was powerful enough to push entire continents across the surface of the Earth. His suggested explanations (centrifugal force, tidal forces) were shown to be far too weak. Without a convincing "how," even strong "what" evidence was not enough.
The answer came decades later, in the 1960s, when scientists discovered seafloor spreading — new ocean floor being created at mid-ocean ridges and pushing outward in both directions. This provided the missing mechanism: continents are not plowing through ocean floor like ships through water. Instead, they are passengers riding on huge slabs of Earth's outer layer (tectonic plates) that are moved by forces in the mantle below. Wegener was right about the observation but wrong about the mechanism. His story is a powerful example of how science works — good evidence eventually wins, even when the initial explanation needs revision.