In 1912, a German meteorologist named Alfred Wegener stood in front of the Geological Association in Frankfurt and argued that the continents had once been joined and were still drifting apart, and geologists mocked him for the next forty years — until sonar maps of the Atlantic seafloor in the 1950s showed a ridge splitting exactly where he had drawn it

Wegener was right about the pattern and wrong about the mechanism, and the geologists who rejected him were right to reject the mechanism he proposed. The coastlines of West Africa and eastern South America looked like the two halves of a torn page. Igneous rocks near Rio de Janeiro matched igneous rocks in South Africa. A handful of scientists in the southern hemisphere, familiar first-hand with the rocks of Africa and South America, kept teaching it. The mechanism Wegener proposed did not work.