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Magnetic Earth

StarDate: 
April 8, 2013

Canada’s about to lose a landmark to Russia. Earth’s north magnetic pole has been in northern Canada since its location was first charted almost two centuries ago. But it’s moving at a rate of close to 40 miles per year. Before long, it’ll be in Russia.

Changes in the magnetic field are nothing new. Its direction and strength vary all the time - on geological timescales, anyway. And sometimes, the field does a complete flip - the north magnetic pole becomes the south pole and vice versa. The last one happened almost 800,000 years ago, and we may be about due for another.

The magnetic field originates deep inside our planet. Earth has an inner core of solid iron that’s as hot as the surface of the Sun. It’s surrounded by a liquid outer core. The two rotate at slightly different speeds. And the outer core is stirred up by heat from the inner core, as well as Earth’s rotation. That creates electric currents, which in turn generate the magnetic field.

The history of the field is preserved in rocks, which are imprinted with the magnetic field as they cool. They show that the field has reversed many times. But they also show that it may take thousands of years to complete a reversal. And there’s no evidence that the magnetic field disappears during these events, it just gets a lot weaker.

A magnetic flip would require some changes - not just from people, but from animals that use the magnetic field to get around. More about that tomorrow.

 

Script by Damond Benningfield, Copyright 2013

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