Anyone who has looked at a world map has felt the temptation. The bulge of Brazil seems made to nestle into the hollow of West Africa; the two coastlines look like the torn halves of a single sheet of paper. Most people notice it and move on. In 1911, a young German meteorologist named Alfred Wegener noticed it and could not let it go.
Wegener was an outsider to geology — an atmospheric scientist and Arctic explorer, more at home ballooning and trekking across Greenland ice than debating rock strata. Perhaps that is why he was willing to entertain an idea the professionals found absurd. He proposed that the continents were not fixed in place but had once been joined in a single vast landmass, which he named Pangaea, "all-earth," and had since drifted apart across the face of the planet. He laid out the case in 1912 and expanded it in his 1915 book, translated as The Origin of Continents and Oceans.
The evidence nobody could unsee
His argument went far beyond the jigsaw coastlines. Identical fossils turned up on continents now separated by oceans. Mesosaurus, a small freshwater reptile that could never have swum the Atlantic, was found in both South America and southern Africa. Fossils of the fern-like plant Glossopteris were scattered across South America, Africa, India, Australia and Antarctica — a distribution that made sense only if those lands had once been adjacent. Bands of distinctive rock and ancient mountain chains ran off the edge of one continent and reappeared on another, like a torn newspaper whose print lines up when the pieces are rejoined. Coal seams, the residue of steamy swamps, sat in the frozen Arctic; glacial scars from ancient ice sheets marked lands now baking near the equator. The climate zones had moved — or the continents had.
The evidence was suggestive, even compelling. The problem was the mechanism. Wegener could not explain what force could shove entire continents through the solid rock of the ocean floor. His own guesses — that continents ploughed through the seabed, driven by the Earth's rotation or by tidal forces — were physically weak, and his critics pounced. Leading geologists, especially in Britain and America, dismissed the whole idea. One prominent scientist called it "delirious ravings"; another warned that anyone who believed it should forget everything learned in geology and start over. It did not help that Wegener was a foreigner, a meteorologist trespassing in their field, publishing in German just as the First World War poisoned scientific goodwill.
Wegener never saw his vindication. In 1930, on his fourth expedition to the Greenland ice cap, he set out across the interior to resupply a stranded weather station and died in the cold, probably of heart failure, around his fiftieth birthday. His body was left where his companions buried it, sealed forever into the ice he had spent his life studying.
The seafloor tells the truth
For two decades his theory languished as a curiosity. Then, after the Second World War, new tools revealed the ocean floor that Wegener had never been able to explain. Surveys found a vast mountain range running down the middle of the Atlantic. In the early 1960s the geologist Harry Hess proposed seafloor spreading: molten rock wells up along that mid-ocean ridge, hardens, and pushes the older seabed outward on either side, so the ocean floor is a conveyor belt continually made at the ridge and destroyed at deep trenches.
The clinching proof came from magnetism. As new seafloor cools, iron minerals in it freeze in the direction of Earth's magnetic field, which flips polarity every so often. Surveys of the seabed revealed symmetrical stripes of alternating magnetism running parallel to the mid-ocean ridge — a mirror image on each side, like a tape recording of the planet's magnetic reversals. Fred Vine, Drummond Matthews and Lawrence Morley read those stripes, in 1963, as direct evidence that the seafloor was spreading exactly as Hess had said. The continents were not drifting through the ocean floor; they were riding atop moving plates of the Earth's crust.
By the late 1960s these insights had fused into the theory of plate tectonics, one of the great unifying frameworks of modern science, explaining earthquakes, volcanoes, mountain-building and the shape of the world in a single scheme. Wegener had been wrong about the mechanism and right about almost everything else. His story became science's favourite parable of the vindicated heretic — proof that a good idea can be laughed out of the room and still turn out to be the ground beneath everyone's feet.
Quiz nuggets
- Alfred Wegener, a German meteorologist, proposed continental drift in 1912 and his 1915 book, naming the ancient supercontinent Pangaea.
- His evidence included matching coastlines and shared fossils such as Mesosaurus and the plant Glossopteris across separated continents.
- The theory was widely ridiculed because Wegener could not explain a mechanism to move continents.
- Wegener died on the Greenland ice cap around 1930 and never saw his ideas accepted.
- Vindication came in the 1960s through Harry Hess's seafloor spreading and magnetic-stripe evidence, leading to plate tectonics.