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The Earth’s magnetic field is weakening, and that could lead to a flip in the planet’s poles making compasses point south instead of north for the first time in almost a million years, say scientists.

Experts at the American Geophysical Union in San Francisco say the field has declined 10 percent in the last 150 years, and suggest a reversal could lead to problems in navigation and a jump in cancer rates with a diminished ozone layer.

“Is a reversal coming? Yeah, it’s coming for sure – sometime,” said geologist Robert Coe of the University of California-Santa Cruz, according to the San Jose Mercury News.

Physicists say the average period between pole flips is about 200,000 years, and the last one is believed to have taken place 780,000 years ago, making the next swap long overdue.

According to Harvard University’s Jeremy Bloxham, the field could disappear completely within the next 2,000 years if the rate of decline remains constant, but he’s not certain if the poles will actually reverse.

“Chances are this is going to die out,” he said, reports the San Mateo County Times. “Reversals are pretty rare.”

If a flip did take place, it would be over the course of several thousand years, and scientists say it would likely reduce the protective ozone layer, cause glitches in satellites and electronic products, and create a flurry of navigational anomalies as compasses would “cease to be a simple means of navigation,” according to Bloxham.

The consequences would be the same if a reversal takes place or the field continues to diminish, with one researcher estimating an additional 100,000 cancer cases annually as people would be subject to more of the sun’s harmful rays.

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