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Earth's magnetic field reverses itself

RESEARCHERS HAVE developed a method of identifying magnetic signals in geological strata and have used the new method to show that the Earth's magnetic field did reverse itself 10 million years ago.

Particles of iron in sediments orient themselves in accordance with the local magnetic field of the earth.

As the sediment consolidates and lithifies over the course of several decades, the particles of iron continue to lie in the direction of the original magnetic field. They thus preserve data on the state of the magnetic field when the sediment was being deposited. These data are used worldwide to date geological strata.

The researchers developed a method, which provides information on the carriers of the magnetic signal in sediments. Carriers include the iron oxides magnetite and hematite, a report in NWO Research Reports said.

Using this method, researchers were able to demonstrate that a short-lived change in the earth's magnetic field did take place about ten million years ago. Hitherto, researchers had been unable to exclude the possibility that subsequent chemical or physical processes had altered the magnetic signal in the sediment.

The earth's magnetic field now points south, meaning that a compass needle points north. Some 800,000 years ago, a compass needle would have pointed south, having previously pointed north.

Changes in the direction of the earth's magnetic field are referred to as reversals.— PTI

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