A Short History of Nearly Everything: Chapter 12 Summary & Analysis

In 1955, Charles Hapgood argues that continental drift—the theory that Earth’s landmasses are in motion—is a hoax. He’s arguing against a growing body of scientific work which suggests that the continents originated as a single landmass but have since split and moved. This is based on evidence ranging from the shapes of coastlines to the presence of identical rocks and fossils on both sides of the Atlantic. 

The first credible scientist to advance the idea of continental drift theory is German meteorologist Alfred Wegener, whose work comes to prominence in the years following World War I. In this era, the geological community is at pains to find a theory of how land moves over time that can account for confusing phenomena, such as the varying ages of mountains. The prevailing theory at this time is that land moves, but only up and down, so theoretically all mountains should be roughly the same age. Despite the explanatory power of Wegener’s claims, geologists dismiss them; Wegener is a meteorologist, after all, with little geological training. To explain away Wegener’s ideas, geologists invent bizarre theories without evidence, such as the prehistoric existence of land bridges between continents that allowed animals to migrate across oceans.

Wegener’s theories begin to gain traction only in the mid-40s after English geologist Arthur Holmes theorizes how continents move: radioactive warming from deep inside Earth causes convection currents powerful enough to move land masses. This basics of this theory are still accepted today.

Meanwhile, mineralogist and naval officer Harry Hess discovers during World War II (from military surveying equipment on his ship) that the ocean floor contains canyons, trenches, and Earth’s most extensive mountain range. These mountains, the mid-Atlantic ridge, stretch south from Iceland down below Africa, on to Australia, and across the Pacific to California. Oceanographers also realize that the ocean floor is much younger where the mid-Atlantic range is, but they’re puzzled as to why.

Meanwhile, British graduate students Patrick Blackett and S. K. Runcorn also discover that the direction of iron particles in British rock are facing the wrong way. Iron particles in rocks line up with Earth’s magnetic poles when the rock is formed, but the iron particles in the rocks they discovered weren’t facing the right direction—meaning that Britain has moved to where it is from somewhere else. Their findings, however, are largely ignored until British geophysicists Drummond Matthews and Fred Vine combine all these ideas to conclude that the sea floor is spreading apart and that continents are in motion, giving rise to “plate tectonics.”

Although many geologists resist plate tectonics theory well into the 1970s, scientists now hold that Earth’s crust is made of up to 32 plates that move in different directions and that modern landmasses moved significantly more than initially estimated. Bryson notes that Kazakhstan, for example, was once attached to Norway and New England. Scientists predict that eventually, California will separate and become a Pacific island, while Africa will push up into Europe, replacing the Mediterranean Sea with a mountain range. The scientific community admits that there are still many unexplained mysteries, like why some places—like Denver and parts of Africa—are rising without tectonic activity at all.