COLUMBUS (WCMH) — Some 780,000 years ago, Earth experienced a reversal of the magnetic poles, weakening the protective magnetic field that surrounds our planet.
Scientists say this has happened five times in the past 10 million years. The question is whether the magnetic poles could reverse in our lifetimes; and if that happened, what would the impacts be?
Dr. Wendy Panero, an OSU Earth Sciences professor, studies how materials behave under intense heat and pressure in the interior of the Earth. She said the reversal of Earth’s magnetic field “is harder to predict than the stock market.”
Panero pointed out that the intensity of the magnetic field has been slowly decreasing (about 5 percent per century) during the past 160 years. However, she noted that we are simply drifting back to a “normal” mode, and then it would take another 20,000 to 40,000 years for a possible reversal of the magnetic poles.
Panero said not to think of Earth’s magnetic pole as a bar magnet. The processes driving the magnetism are generated by turbulent liquid motions in the outer core of our planet, where molten iron and nickel move about vigorously and conduct electricity.
A magnetic pole reversal could result in more than one pair of poles (North Magnetic and South Magnetic Pole), and aurorae would be observed at any latitude. A greater concern would be less shielding of Earth from high-energy particles and cosmic rays, whisked through space by the solar wind, with possible impacts including potential damage to the electrical grid and satellites.
Dr. Lonnie Thompson, an OSU paleoclimatologist in the School of Earth Sciences, sees a strong link “between the reversal of the magnetic poles and the cosmogenic nuclei (chlorine-36 and beryllium-10) record of these events.”
“These cosmogenic isotopes get deposited on the glaciers, lakes and oceans of the world and can be used as time markers. We are currently developing a time scale for a very old ice core we recently recovered from far western Kunlun mountains of Tibet. These cores are the oldest recovered outside the polar regions,” Thompson said.
Short-term magnetic field reversals, called geomagnetic excursions, last a few thousand years, when Earth’s geomagnetic field weakens dramatically, a process that occurs in the molten layer outside the solid planetary core.
Radioactive material embedded in ice cores revealed such events between 39,000 and 41,000 years ago (Laschamp excursion), and a 1,200-year event 32,000 to 34,000 years ago (Mono Lake excursion).
Regarding a slight increase in solar radiation during a period when the magnetic field weakens, he said, “We do not have good documentation on how these events might have impacted human health, or indeed the climate of the earth.”
“We really don’t understand the driving mechanisms of a collapse of the magnetic field,” Thompson said.