Tag: length of day

Chile Quake Shifted Earth's Axis, Shortened the Length of a Day

By Smriti Rao | March 2, 2010 11:03 am

Earth-North-America-cloudsThe devastating earthquake in Chile that killed almost 700 people probably also shifted the Earth’s axis, say NASA scientists, permanently making days shorter by 1.26 microseconds. But since a microsecond is one-millionth of a second, you may not have noticed.

Richard Gross, a geophysicist at NASA’s Jet Propulsion Laboratory, says he has done the calculations. Gross says the earthquake, which measured 8.8 on the Richter scale, moved large amounts of rock, altered the distribution of mass on the planet, and moved the Earth’s axis by about 2.7 milliarcseconds (about 8 centimeters or 3 inches). The change in axis directly impacts Earth’s rotation, and the rate of the planet’s rotation determines the length of a day.

To explain this phenomenon, scientists used an ice skating analogy: When a skater spins on ice, he draws his arms closer in to his body to spin faster, because the speed of his rotation is dependent on the way mass is distributed across his body.

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