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Mon Aug 19, 2019, 08:12 PM

Earth's inner core is doing something weird

Source: National Geographic

Earth's inner core is doing something weird

Data from old Soviet weapons tests are helping scientists get a high-resolution look inside our planet.



ON SEPTEMBER 27, 1971, a nuclear bomb exploded on Russiaís Novaya Zemlya islands. The powerful blast sent waves rippling so deep inside Earth they ricocheted off the inner core, pinging an array of hundreds of mechanical ears some 4,000 miles away in the Montana wilderness. Three years later, that array picked up a signal when a second bomb exploded at nearly the same spot.

This pair of nuclear explosions was part of hundreds of tests detonated during the throes of Cold War fervor. Now, the records of these wiggles are making waves among geologists: They have helped scientists calculate one of the most precise estimates yet of how fast the planetís inner core is spinning.

Surface-dwellers know that Earth spins on its axis once about every 24 hours. But the inner core is a roughly moon-size ball of iron floating within an ocean of molten metal, which means it is free to turn independently from our planetís large-scale spin, a phenomenon known as super-rotation. And how fast itís going has been hotly debated.

Capitalizing on the zigzagged signals from those decades-old nuclear explosions, John Vidale, a seismologist at the University of Southern California, now has the latest estimate for this rate. In a recent study published in Geophysical Research Letters, he reports that the inner core likely inches along just faster than Earthís surface. If his rateís right, it means that if you stood on a spot at the Equator for one year, the part of the inner core that was previously beneath you would wind up under a spot 4.8 miles away.


Read more: https://www.nationalgeographic.com/science/2019/08/earths-inner-core-spinning-surprisingly-slow-nuclear-tests-reveal/


Related: Very slow rotation of Earth's inner‐core from 1971 to 1974 (Geophysical Research Letters)

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