Every 200,000-300,000 years, the earth's magnetic poles change places. What was once the North Pole becomes South Pole and vice versa. This is a time of invisible shocks.
The last reversal was unusual. For some reason, the poles remained oriented as they are now, about three quarters of a million years ago. New research has revealed some of the details of this turn.
The study of the Earth's magnetic field is called paleomagnetism. It includes the study of rocks and sediments, and sometimes archaeological materials. Stones that were once molten retain a record of the Earth's magnetic field as they solidify.
The related field of magnetostratigraphy studies the records of geomagnetic reversals that are contained in these rocks. By dating the rocks, researchers can plot the changes in the Earth's position in the opposite direction.
The last reversal is named the Matuyama-Brunes geomagnetic reversal in honor of the co-authors of the discovery: French geophysicist Bernard Brunes and Japanese geophysicist Motonori Matuyama. Over the years since the discovery, researchers have tried to understand exactly when this happened, as well as how long it took to change the poles.
The new study is titled 'Matuyama-Brunes Geomagnetic Reversal Complete Sequence in Chiba Composite Section, Central Japan'. The lead author is Yuki Haneda, a project researcher at the National Institute for Polar Research and Research Fellow at the National Institute of Advanced Industrial Science and Technology in Japan.
The article was published in the journal Progress in Earth and Planetary Science.
More accurate data can be found in some sediments that can form over a long period of time. One of these deposits is called the Chiba composite section. It is located in Japan, and geophysicists believe it is a very detailed record of the Matuyama-Brunes reversal.
The study says it took about 20,000 years, including a 10,000-year period of instability that led to the reversal.
“Our data is one of the most detailed paleomagnetic records during the Matuyama-Brunhes geomagnetic reversal, offering a deep understanding of the geomagnetic reversal mechanism,” Haneda said.
Marine fossils and pollen found in the Chiba composite section also indicate magnetic field reversal. A team of researchers is going to investigate the fossils and pollen to try to find out more.
In any case, life on Earth has experienced many geomagnetic reversals, and yet life is flourishing. Modern people have not yet encountered a similar phenomenon, so watching the next one will be very instructive.
Most likely, the reversal of the poles will affect our power and communication systems, including satellites.
While the study cannot answer questions about what awaits us at the polarity reversal, it allows us to better understand the previous reversal.
Article published by Universe Today.
