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The Expanding Earth Animation

Why It Is Really a Plate-Tectonic Animation


The Expanding Earth Animation

Source: Müller et al. 2008

American Geophysical Union image

In my line of work I attract a set of people who believe that plate tectonics is all wrong. They offer a different theory in which the Earth is growing in size. But their favorite illustration of Earth expansion is actually a beautiful, mind-expanding demonstration of plate tectonics.

Expanding Earth

Expanding-Earth theory was primarily the invention of Australian geologist Sam Carey. In the 1930s he was exploring the "continental drift" theory of Alfred Wegener, which is familiar today but back then was widely thought a crazy scheme. He took the trouble to build a large half-globe, on which he maneuvered models of the continents to explore Wegener's idea that all the world's continents had once been united in a single mass called Pangaea. He came to believe that the continents fit together properly only if the globe were shrunk. Indeed, he could shrink the globe enough to fit them all into a single world-encompassing continent without any ocean basins at all. That did away with the problems of reassembling Pangaea.

This vision drove Carey for the rest of his long life. He had a lot of fun working out details, and his prodigious knowledge of world geology gave him plenty of foo d for thought. Mountain ranges in their curving lines, long seafloor chasms and island chains, the patterns of earthquakes and eruptions, all helped him paint vivid portraits of a planet bursting its seams and stretching into its modern state, with two distinct kinds of crust. The original continental crust remained in today's torn pieces, with the newer and different oceanic crust between them. In the small community of geologists working on the largest scale, his theory and his forceful personality took him far. (Indeed, his term "orocline," a bend in a mountain range, is still in the working vocabulary.) At the time of Carey's heyday, well into the 1950s, Earth expansion was a legitimate hypothesis.

Newer discoveries and the more fruitful theory of plate tectonics won the day. But Carey's haunting vision of a single crust tearing apart into continents is a mainstay of today's scatter of expanding-Earthers. The picture is hard to shake until you learn to see it differently. Then its power disappears while its charm remains.

Analyzing the Animation

Take a look at it now, courtesy of Wikipedia. Even better, watch this animation, one of several made by Neal Adams, a talented graphic artist, using modern data.

The animation relies on a well-established geological fact that I will put in everyday terms: every continent in the world today has torn edges. Saying it another way, every ocean in the world today arose as a rift in a preexisting continent. On this, expansionists and plate-tectonicists agree.

However, today there is essentially no oceanic crust that is older than 200 million years. Carey swore that anything older never existed and that there is nothing more to say. Plate tectonics explains that oceanic crust is constantly recycled, swept downward into the mantle by subduction. Subduction allows continents to drift around, merge into supercontinents, and break up again indefinitely, a concept taught as the Wilson Cycle. Subduction also allows geologic history to make sense beyond 200 million years ago. It turns out that there's a lot more to say.

Plate tectonics paints a picture of continental crust constantly rearranging itself. In this scenario, every continent eventually gets all of its edges ripped. In a steady-state Earth like this, you can always interpret the result as an expanding Earth purely from geometry. Every edge, if you go back long enough (200 million years), will find its counterpart on another continent. It only looks like the Earth must shrink to accomplish this. It's an optical illusion stemming from a conceptual illusion.

And you can only believe that illusion if you can do two things: deny that subduction exists—that is, if you ignore GPS measurements that prove it—and treat the continental crust as a featureless blank, with no history of its own—that is, if you ignore basic regional geology.

Plate Tectonic Animations

There are animations based on plate tectonics, but scientists make them so they aren't as pretty. See a set of them from the National Park Service. They go back farther than 200 million years, and they include a lot of details inside the continents from those older days. Tanya Atwater, who was an artist before becoming a geologist, has been creating geologic animations in much greater scientific detail for over 40 years.

These animations take account of evidence within the continents showing collision zones, where ancient oceans have closed shut, just as the Pacific and Mediterranean are shrinking today. The animations go billions of years back. Plate tectonics has gone on effectively forever. Expanding-Earthers cannot explain the presence of former oceans, shown by sutures where ancient continents once merged. The ones who show up to dispute my blog posts appear to have a total blind spot on this topic.

Today we explain Carey's problem with the continents as a failure to recognize that, among other things, (1) Pangaea was not a single clean continent but an evolving assemblage like modern Asia, (2) continents are not truly rigid and can be deformed, and (3) the seafloor is recycled by subduction. No one knew these things in his heyday.

Carey could not admit subduction without destroying his theory; his arguments grew desperate in the 1970s and 1980s as the data grew compelling. Today's expanding-Earthers exert their harshest language against subduction, unleavened by any of Carey's gifts. To me, their denialism adds a perverse charm to their favorite animation.

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