Evidence for a rapid change in the geomagnetic field 41,000 years ago

Recent magnetic research conducted by the German geoscience research center GFZ sheds light on a short-lived and erratic change in the Earth’s geomagnetic field that occurred about 41,000 years ago during the last ice age. This event, known as a geomagnetic deviation, resulted in a complete reversal of the positions of magnetic north and magnetic south. Evidence of this global event has been obtained not only from the Black Sea, but also from the North Atlantic, South Pacific and Hawaii. Sediment cores also provide further evidence of the last ice age and supervolcano eruption.

Pole inversions are a natural phenomenon

Pole inversions are a natural phenomenon that has been occurring on Earth for millions of years. Several pole inversions have occurred over the past 20 million years, with a complete pole inversion occurring about every 200,000-300,000 years. The last major pole inversion, known as the Brunhes-Matuyama inversion, occurred about 780,000 years ago. Typically, pole reversals take between 1,000 and 10,000 years.

Minor changes in living and natural environments

Interestingly, the Brunhes-Matuyama inversion did not cause drastic changes in plant or animal life, as evidenced by the paleontological record. The study of oxygen isotope ratios in deep ocean sediment cores also revealed no changes in glacier activity during this period.

Consequences of geomagnetic deviation

The geomagnetic deviation that occurred about 41,000 years ago had serious consequences for the Earth. The reverse polarity field geometry lasted about 440 years, and the field strength was only about 25% of today’s field. The actual polarity lasted only 250 years, greatly reducing the Earth’s protection from harsh cosmic rays. This resulted in increased radiation exposure and was confirmed by peaks of radioactive beryllium (10Be) in Greenland ice cores.

Role of cosmic rays and solar activity

10Be is formed in the Earth’s atmosphere as a result of cosmic rays colliding with atoms. The half-life of 10Be is 1.36 million years. Periods of high solar activity reduce the flux of cosmic rays hitting the Earth, resulting in reduced production of 10Be. Studies show that during the geomagnetic deviation 41,000 years ago, 10Be production was inversely proportional to solar activity and solar wind amplification.

The Lachampa event: a precursor to the geomagnetic deviation

The Lachampa event, which occurred about 45 years ago, was the first documented case of geomagnetic deviation. Analysis of the magnetization of lava flows in the Massif Central in France showed a significant deviation from the direction of the modern geomagnetic field. This event, known as the Laschamp event, gave rise to studies of geomagnetic deviations during the last ice age. Recent GFZ studies have provided a more complete picture of the geomagnetic deviation 41,000 years ago.

Studies of geomagnetic deviation 41,000 years ago allow us to better understand the nature and frequency of pole inversions on Earth. These changes in the polarity of the magnetic field have consequences for our planet, including increased irradiation and changes in solar activity. However, as the paleontological record shows, the Brunhes-Matuyama inversion did not cause significant changes in living and natural environments. These studies are an important step in understanding the geologic history of the Earth and its magnetic field.

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