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Technology Forecaster; Consulting Associate Professor, Stanford University

Plate Tectonics Elegantly Validates Continental Drift

Plate Tectonics is a breathtakingly elegant explanation of a beautiful theory, continental drift. Both puzzle and answer were hiding in plain sight right under our feet. Generations of globe-twirling school children have noticed that South America's bulge seems to fit in the gulf of Africa, and that Baja California looks like it was cut out of the Mexican mainland. These and other more subtle clues led Alfred Wegner to propose to the German Geological Society in 1912 that the continents had once formed a single landmass. His beautiful theory was greeted with catcalls and scientific brickbats.

The problem was that Wegner's beautiful theory lacked a mechanism. Critics sneeringly pronounced that the lightweight continents could not possibly plow through a dense and unyielding oceanic crust. No one, including Wegner could imagine a force that could cause the continents to move. It didn't help that Wegner was an astronomer poaching in geophysical territory. He would die on an arctic expedition in 1931, his theory out of favor and all but forgotten.

Meanwhile, hints of a mechanism were everywhere, but at once too small and too vast to see with biased eyes. Like ants crawling on a globe, puny humans missed the obvious. It would take the slow arrival of powerful new scientific tools to reveal the hidden forensics of continental drift. Sonar traced mysterious linear ridges running zipper-like along ocean floors. Magnetometers towed over the seabed painted symmetrical zebra-striped patterns of magnetic reversals. Earthquakes betrayed plate boundaries to listening seismographs. And radiometric dating laid out a scale reaching into deep time.

Three decades after Wegner's death, the mechanism of plate tectonics emerged with breathtaking clarity. The continents weren't plowing through anything—they were rafting atop the crust like marshmallows stuck in a sheet of cooling chocolate. And the oceanic crust was moving like a conveyor, with new crust created in mid-ocean spreading centers and old crust subducted, destroyed or crumpled upwards into vast mountain ranges at the boundaries where plates met.

Elegant explanations are the Kuhnian solvent that leaches the glue from old paradigms, making space for new theories to take hold. Plate tectonics became established beyond a doubt in the mid-1960s. Contradictions suddenly made sense, and ends so loose no one thought they were remotely connected came together. Continents were seen for the wanderers they were, the Himalaya were recognized as the result of a pushy Indian plate smashing into its Eurasian neighbor, and it became obvious that an ocean was being born in Africa's Great Rift Valley. Mysteries fell like dominoes before the predictive power of a beautiful theory and its elegant explanation. The skeptics were silenced and Wegner was posthumously vindicated.