Strength of the Earth’s magnetic field has sharply decreased several times over the past 9 thousand years

(ORDO NEWS) — Geologists have found that over the past nine thousand years, the Earth‘s magnetic field has weakened several times.

This led to the appearance of magnetic anomalies. The last similar episode occurred about 2.5 thousand years ago, the researchers write in an article published in the journal PNAS.

Geophysicists believe that the position of the Earth’s magnetic poles is not constant: they periodically change places.

Sometimes such shifts are temporary, as was the case 40,000 years ago, and other times, as about 780,000 years ago, they become permanent.

Scientists recently discovered that the strength of the planet’s magnetic field has been declining over the past few centuries.

This happens especially quickly in the southern part of the Atlantic, off the coast of Brazil and Africa. The magnetic field in this region, which the researchers called the South Atlantic anomaly, has become so weak that it almost does not protect satellites flying over it from the effects of cosmic rays and charged particles.

A group of geologists decided to find out if similar changes occurred in the past. To do this, they analyzed the results of measurements of the magnetization of ancient rocks and, based on this information, created a computer model of the Earth’s interior.

The researchers note that the model took into account the distribution of large flows of liquid matter inside the Earth’s core and how their movement affects the strength, direction of the magnetic field and the position of the “magnetic center” of the planet.

Using the approach, scientists calculated changes in the strength of the Earth’s magnetic field over the past nine thousand years and found that our planet has experienced several declines in strength.

One of the longest and sharpest declines occurred even before the dawn of civilization – about 7-8 thousand years ago, and the penultimate decline occurred at the end of the ancient era, in the middle of the 1st millennium BC.

Calculations have shown that magnetic anomalies quite often appear in different regions of the Earth during those periods of time when the total field strength falls, and the “magnetic center” of the planet moves far away from its axis of rotation.

For this reason, scientists expect that the existing changes off the coast of Brazil and in the vicinity of the South African Limpopo River will disappear in the next 300-400 years, when the strength of the Earth’s magnetic field begins to gradually increase.


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