Nova: Earth's Magnetic Fields

And how does pottery help reveal these things? Watch until around 19 min. 

Since the 1970s, the magnetic north pole has moved more than 1500 km at a rate of 10 kilometres a year. In the 1980s, this increased to 30 km a year. Today, the Pole travels 50, even 60 km - close to 150 metres a day.

Scientists don't quite know why its speed has increased these past 20 years. The magnetic pole is moving northwest of the geographic pole and may soon be across the Arctic Ocean in Siberia.
To find their bearings, sailors the world over must know the exact angle of difference between the two geographic and the magnetic north poles: the 'magnetic declination.'

The magnetic pole moves from the North to the South and vice versa every 250,000 years on average and does it very suddenly. Over 180 reversals have been recorded already.

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