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Did You Know: Magnetic Reversals

Every so often, Earth's magnetic field reverses.
Credits

  • Illustration of Earth’s magnetic field today: STScI
  • Illustration of Earth’s magnetic field with reversed polarity: STScI
  • Illustration of magnetic striping on the seafloor: STScI
  • Written by Margaret Carruthers
Transcript

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Text, Did you know? Magnetic Reversals.
 
Every so often, Earth's magnetic field reverses. A diagram of the Earth's poles with radiating magnetic field lines stretching into space. Earth's magnetic field: Normal. Earth is a giant magnet with a magnetic field similar to that of a bar magnet.
 
Currently, Earth's north magnetic pole is in Antarctica, while its south magnetic pole is in the Arctic.
 
But every so often, the poles reverse. The north magnetic pole becomes the south magnetic pole, and vice versa.
 
The polarity of the magnet in the diagram reverses. Earth's Magnetic Field: Reversed.
 
A close up of the Arctic ocean around Greenland. Evidence for these reversals is fossilized in ancient lavas. A zoomed in excerpt of a mid-ocean ridge south west of Iceland shows rocks with regular and reversed magnetic polarity. The lavas become magnetized in the direction of Earth's magnetic field as they cool and turn solid.
 
The last major reversal occurred about 780,000 years ago.