Magazine article Science News

Putting a New Spin on Earth's Core

Magazine article Science News

Putting a New Spin on Earth's Core

Article excerpt

By eavesdropping on earthquake vibrations passing through the globe's innards, seismologists have discovered that Earth's solid core is a solo dancer, spinning separately from the rest of the planet.

Earth's metallic core consists of a solid iron sphere, about three-quarters of the size of the moon, sitting within an outer shell of roiling liquid iron.

Hidden beneath 2,600 kilometers of rock, the core has remained the most cryptic realm of our planet. Some theorists have argued that electromagnetic forces inside Earth should cause the core to spin separately from the planet's outer layers. Others have hypothesized that the core should spin in synchrony with the mantle and the crust.

Xiaodong Song and Paul G. Richards of the Lamont-Doherty Earth Observatory in Palisades, N.Y., have found that the inner core rotates in the same direction as the rest of the planet but about 1#161# per year faster. They report their observation in the July 18 Nature.

The surface of the core, at its equator, is moving about 20 km per year relative to the liquid outer core. "That's 100,000 times faster than the types of motion we normally associate with properties of the solid Earth," says Richards. In contrast, the continents creep across Earth's surface at only a few centimeters per year.

Song and Richards embarked on their research after a computer simulation at Los Alamos (N.M.) National Laboratory predicted that Earth's core should spin 1#161# to 2#161# faster per year than other parts of the planet.

Gary A. Glatzmaier of Los Alamos says he was surprised that Song and Richards could actually observe the core's rotation. "We were really excited to hear that they had found this," says Glatzmaier.

The Lamont-Doherty scientists could not have detected the core's movement without the help of recent discoveries about inner Earth. …

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