Flipping poles: Studies suggest that the Earth's magnetic field (pictured) is reducing, of concern because it protects us from the ravages of solar wind.

Credit: NASA

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SYDNEY: A reversal of the Earth's magnetic poles could happen sooner than we think, according to Dutch scientists who report that the planet's magnetic field is becoming gradually less stable.

A reversal could affect everything from navigation and communications equipment to the composition of the atmosphere, say experts.

The report, published today in the U.K. journal Nature Geoscience, found that reversals have been far more common in the last 200 million years than they were deep in the planet's history.

Wandering poles

Researchers, led by Andrew Biggin of the University of Utrecht in the Netherlands, made the discovery by analysing rocks formed between 2.45 to 2.82 billion years ago.

The story of the Earth's magnetic field is written in rocks over time. Because these rocks become 'magnetised' at the time of their formation, scientists can discover which direction the poles were facing and how strong the Earth's magnetic field was at that time.

The magnetic poles wander around the vicinity of the geographic poles all the time – the north magnetic pole currently resides in the Canadian Arctic. However, at relatively regular intervals throughout the 4.5 billion year history of the planet, the magnetic poles have flipped completely. A few thousand years before a reversal, the magnetic field gradually gets weaker; something which could cause problems for inhabitants of the planet.

"The Earth's magnetic field is important for shielding the atmosphere, and us, from damage caused by the solar wind," explained Biggin. "It's also used by us and other species for navigation". An increase in solar wind would disrupt communications equipment and power grids.

Current records suggest that we are long overdue for our next reversal, he said. "On average, there is a reversal around every 400,000 years, but this varies a lot." The geological record suggests that the last reversal was around 800,000 years ago.

Furthermore, there is already evidence to show that the field has been weakening over the last few centuries – some archaeological remains suggest that the field was far stronger in the time of the Roman Empire, some 2,000 years ago.

Don't throw away your compass

Don't throw away your compass just yet though – major changes may not even happen in our lifetimes. "The reversal process is very unpredictable," said Biggin. "We could be heading into a reversal in the next few centuries, or we might be waiting another million years".

Even then, reversal is a slow process, which can take some thousands of years to complete.

But what about the effect on living organisms? Another paper, published in Nature in March suggested that some species that rely on the field for navigation or orientation have taken a knock from pole reversals in the past.

Author David Gubbins, of the University of Leeds in England, said that some single-celled organisms that relied on magnetism to tell up from down likely went extinct during past reversals. Human beings have survived reversals in the past, however, added Gubbins, "so we are likely to come through the next one unscathed."