it’s so boring, the usual human’s-eye view. Seasons come and go, but terra fi rma itself never varies. Even
an earthquake or a mudslide seems like a random incident unconnected to any larger or more complex patterns. But put on the lenses of a geologist and take another look. Reading the stories imprinted on the rocks and crystals gives scientists the ability to examine our world as it has evolved over millions, even billions, of years. From this vantage point, it is easy to see that Earth has been—and continues to be—a lively cauldron of change. Just as stop-action photography shows how buds burst into flower, geology gives us a picture of a living, changing planet. It even has a heartbeat of sorts, in pulsed releases of vast amounts of inner heat.
In another place where taking the long view alters our everyday notions, we learn that erosion—long familiar as the great leveler—has also had a hand in shaping the tallest peaks, the Himalayas. Eroding land, by reducing weight, accelerates tectonic processes, creating an uplift. Deep under the morphing surface, the interior simmers. The churning mantle creates and powers the primary magnetic field that surrounds the sphere. The polarity of this field reverses every so often, which has long puzzled researchers.
This special edition of Scientific American offers a rare look inside the mysterious and little appreciated underfoot activities of the world we all call home.
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