National Geographic News, Reporting Your World Daily

Monday, November 23, 2009

Photo: Shifts in Earth's Magnetic Field Driven by Oceans?


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The widely accepted dynamo theory says that Earth has a magnetic field because it has a solid core spinning inside a rotating, electrically conductive liquid core (above, an illustration shows Earth's interior).

But a controversial study published in June 2009 challenges that theory by saying tiny changes in Earth's magnetic field—for now the main proof of the dynamo—are actually driven by ocean currents, not circulation in the liquid core.

Illustration by Jason Reed, Photodisc/Photolibrary