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How Earth's wandering poles return home

from Physics World

"True polar wander" is the relative movement between the mantle (and so the surface of the Earth) and the Earth's spin axis or its rotational axis. Researchers believe that over the past 1 billion years, the Earth's surface has "tipped over" and then returned to its original location six times along the same axis — a process called "oscillatory true polar wander." A team of geophysicists from the U.S. and Canada has reported in Nature their new theory that explains this curious phenomenon. Scientists know that thermal convection from the Earth's mantle to the surface causes mechanical deformations in the Earth's crust. The new work shows how the mechanical deformations couple with the rotational motion of the planet itself and subsequently leads to "self-righting" dynamics when the rotational axis and mass distribution shift over time. more

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