The days are shorter now, and we wobble more.

Sudden subduction of the Nazca plate carried large amounts of mass closer to the center of the Earth — which, conceptually but on a vastly different scale, works like spinning skaters bringing their arms closer to their bodies, says Richard Gross, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. As a result, Earth’s day is now about 1.26 microseconds shorter than it was before the massive quake, Gross estimates.

And because the quake’s shift in mass occurred deep in the Southern Hemisphere, Earth was slightly tipped off balance — a result similar to a spinning skater bringing in one arm but not the other. The planet’s “figure axis,” the line about which the Earth is balanced, shifted about 8 centimeters, Gross notes.

Earth’s axis is constantly wobbling at various frequencies, with some oscillations measuring several meters and taking months to unfold. Forces driving those cycles, including those resulting from winds and ocean currents, act continually across Earth’s surface and often are about a thousand times larger than those generated during the Chilean quake.

Earth knocked for a loop, Science News, 3/3/10