Although perhaps difficult to comprehend, the Earth’s magnetic field may soon reverse in its polarity. It has, after all, done so many times in history. So says an international team of geologists after examining evidence of a past reversal and indications that the planet’s magnetic field today is growing weaker.

The researchers, who are based in Italy, France, and here in the U.S. at Columbia University and the University of Calironia in Berkeley, found evidence that the most recent planetary magnetic pole reversal occurred approximately 786,000 years ago and happened over a period of less than 100 years.

“It’s amazing how rapidly we see that reversal,” said UC Berkeley graduate student Courtney Sprain in a statement. “The paleomagnetic data are very well done. This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen.”

Recent observations suggest that the intensity of Earth’s magnetic field is decreasing an order of magnitude faster than it has in the past. As a result, some geophysicists predict that a field pole reversal could occur within the next few thousand years.

The planet’s magnetic field may reverse in polarity as a result of convection in the iron core. To date, no evidence has been found that indicates any major catastrophes resulting from the last field flip. However, an inversion today could take out electrical grids through unusual current surges. The Earth’s magnetic field shields life on its surface from solar and cosmic radiation so a disruption before an inversion could exert serious adverse effects on the biosphere.

“We should be thinking more about what the biologic effects would be,” remarked Paul Renne, co-author on the report and director of the Berkeley Geochronology Center.

The researchers describe their findings in a report published in the latest issue of the Geophyscial Journal International.