A short history of nearly everything - Bill Bryson [91]
At all events, plate tectonics not only explained the surface dynamics of the Earth—how an ancient Hipparion got from France to Florida, for example—but also many of its internal actions. Earthquakes, the formation of island chains, the carbon cycle, the locations of mountains, the coming of ice ages, the origins of life itself—there was hardly a matter that wasn't directly influenced by this remarkable new theory. Geologists, as McPhee has noted, found themselves in the giddying position that “the whole earth suddenly made sense.”
But only up to a point. The distribution of continents in former times is much less neatly resolved than most people outside geophysics think. Although textbooks give confident-looking representations of ancient landmasses with names like Laurasia, Gondwana, Rodinia, and Pangaea, these are sometimes based on conclusions that don't altogether hold up. As George Gaylord Simpson observes in Fossils and the History of Life, species of plants and animals from the ancient world have a habit of appearing inconveniently where they shouldn't and failing to be where they ought.
The outline of Gondwana, a once-mighty continent connecting Australia, Africa, Antarctica, and South America, was based in large part on the distribution of a genus of ancient tongue fern called Glossopteris, which was found in all the right places. However, much later Glossopteris was also discovered in parts of the world that had no known connection to Gondwana. This troubling discrepancy was—and continues to be—mostly ignored. Similarly a Triassic reptile called Lystrosaurus has been found from Antarctica all the way to Asia, supporting the idea of a former connection between those continents, but it has never turned up in South America or Australia, which are believed to have been part of the same continent at the same time.
There are also many surface features that tectonics can't explain. Take Denver. It is, as everyone knows, a mile high, but that rise is comparatively recent. When dinosaurs roamed the Earth, Denver was part of an ocean bottom, many thousands of feet lower. Yet the rocks on which Denver sits are not fractured or deformed in the way they would be if Denver had been pushed up by colliding plates, and anyway Denver was too far from the plate edges to be susceptible to their actions. It would be as if you pushed against the edge of a rug hoping to raise a ruck at the opposite end. Mysteriously and over millions of years, it appears that Denver has been rising, like baking bread. So, too, has much of southern Africa; a portion of it a thousand miles across has risen nearly a mile in 100 million years without any known associated tectonic activity. Australia, meanwhile, has been tilting and sinking. Over the past 100 million years as it has drifted north toward Asia, its leading edge has sunk by some six hundred feet. It appears that Indonesia is very slowly drowning, and dragging Australia down with it. Nothing in the theories of tectonics can explain any of this.
Alfred Wegener never lived to see his ideas vindicated. On an expedition to Greenland in 1930, he set out alone, on his fiftieth birthday, to check out a supply drop. He never returned. He was found a few