Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves Read Online Free PDF Page B

the Himalayas, anyway—by a couple of inches a year.2
    Stalactites are mirrored in this reflective pool in Luray Caverns, located in Virginia’s Shenandoah Valley. It typically takes five hundred years for each of these downward-pointing structures to grow one inch.
    A 2006 study showed that mountain ranges typically rise to their full height in only about two million years. Mount Everest has grown measurably taller since it was first scaled. Some activities just keep getting harder.
    Actually, you yourself are moving even when you’re doing the couch-potato thing. All landmasses are shifting, carrying you and your TV toward the west if you live in the United States. You can lie in bed and sing, “California, here I come!” But at half an inch a year, you’d better bring your own trail mix.
    This tectonic drift was first discovered by Abraham Ortelius, a well-regarded Flemish mapmaker, in the late sixteenth century. He wrote, “The Americas were torn away from Europe and Africa… by earthquakes and floods” and went on to note that “the vestiges of the rupture reveal themselves if someone brings forward a map of the world and considers carefully the coasts of the three [continents].”
    Independently, Alexander von Humboldt, in the mid-nineteenth century, while mapping the eastern coast of South America, wrote that its emerging outline seemed like the adjoining jigsaw-puzzle piece for the western side of Africa. The only logical conclusion was that continents shift. But neither of these men was credited with this astonishing revelation. Nor did any other scientists take the idea and run with it. It wasn’t until Alfred Wegener’s 1912 theory of continental drift that people started taking it seriously, even if there remained more critics of it than believers for the next half century.
    Here was a case where you had an effect—landmass motion—before you had any conceivable cause. Yet it always stared us in the face. What’s below Earth’s surface? Lava, obviously—what we now call magma. This is a liquid. Suddenly it seemed plausible that continents float on this thick, dense fluid. And if they float, they obviously could shift. The problem was coming up with a mechanism or force that could propel them sideways. Ever try pushing a stalled car? Imagine the torque required to budge an item like Asia. Continents are not pond scum.
    That’s why the idea of drifting continents was not widely accepted among the top geologists. It was, in fact, ridiculed for decades. No proposed mechanism that seemed truly plausible came forth, at least none in which the math would work. It took until the 1950s and particularly the 1960s before the true reason for landmass motion finally came to light. The cause had been hidden beneath thousands of feet of murky brine.
    It was the dramatic but unknown reality of the sea floor spreading apart. Mid-ocean volcanic activity creates widening fissures and forces a growing separation between the floating continents. The greatest fault line, the Mid-Atlantic Ridge, is the primary point of separation for the earth’s crust. New techniques of seismology and, finally, GPS tracking sealed the deal.
    Nowadays we know of eight separate floating landmasses, each chugging along in various directions. The Hawaiian chain is the fastest moving, as it heads to the northwest at the rate of four inches annually. We can now also easily match geologic features on one continent’s edge with those on another’s, proving they were connected in the not-so-distant past. For example, eastern South America and western Africa not only share specific unique rock formations but also contain matching fossils and even living animals found nowhere else. Similarly, the Appalachians and Canada’s Laurentian Mountains are a perfect continuous match with rock structures in Ireland and Britain. All the evidence proves that the separate continents were once a single supercontinent—the famous Pangaea. It formed three