1912

Continental Drift

Alfred Wegener (1880–1930)

Even to a child, a map of the Earth’s continents can seem like a jigsaw puzzle. If we just move South America next to southern Africa, they line up! Similarly, North America and Greenland line up with northwestern Africa and Europe. Voilà! Despite the apparent intuitive nature of the alignments, the reality of the situation for geologists is that there is no obvious way for continents to have moved or “drifted” through the oceanic crust from those positions to their current ones.

And yet, some scholars, such as the German geologist Alfred Wegener, couldn’t shake the idea that at some point in the past, the continents had indeed been together as one larger landmass. Wegener looked carefully, for example, at rock types and especially plant and animal fossil types on opposite sides of the Atlantic Ocean and found amazing similarities. He also found that some fossil species in tropical India had once flourished in much more temperate latitudes, and surmised that Antarctica, Australia, India, and Madagascar had also once been connected to the eastern side of Africa. In a seminal 1912 research paper, Wegener postulated that all the continents had once been part of a single landmass (an “Urkontinent” in German), and that they have been drifting apart from one another since then.

Wegener’s continental-drift hypothesis was met with stiff resistance from the established geologic community, many of whom viewed Wegener as an outsider. Geologists had major concerns about the mechanism by which continents could move through rigid oceanic crust (Wegener hadn’t solved this), and the rate that Wegener thought the continents were drifting turned out, in later measurements, to be more than 100 times the actual value of relative continental motion. Still, others couldn’t shake the idea, either, and research continued.

Wegener’s hypothesis was ultimately vindicated, in a way, by the mid-to-late twentieth-century discoveries of island arcs, seafloor spreading, and the eventual realization that Earth’s crust is divided into a few dozen large tectonic plates that essentially “float” on the upper mantle and move relative to one another over time. Wegener’s Urkontinent had existed—geologists now call it Pangea. Sometimes, the solution to a puzzle really is as obvious as it seems, but it takes an outsider’s perspective to realize it.

Main image: A 1930 photograph of German meteorologist and geologist Alfred Wegener. Inset: Illustration of an early computer-assisted “fit” of many of the current continents, reconstructing Pangea.