Five hundred million years ago, during the Drumian stage of Middle Cambrian, Earth could have one of the craziest moments in its geomagnetic history as north and south poles flip-flopped nearly 80 times over a 3-million-year-period, the study by geologists from the Russian Academy of Science and the Institut de Physique du Globe de Paris in France, published in Earth and Planetary Science Letters, suggests.
The scientific team studied the tiny particles of magnetite and hematite from crumbling cliffs at the Khorbusuonka River region in Siberia, formed half a billion years ago when the area was underwater. As these magnetized crumbs were locked in the sediments, they work like tiny compasses, frozen in time.
However, around the Middle-Upper Cambrian boundary the intensity of magnetic poles swapping places dramatically decreased to just 1.5 flips per million years for reasons yet unknown, so the researchers concluded that there must have been a hyperactive reversing mode of the geodynamo, generating the field.
As Science Alert points out, the abrupt ending of such turbulent times as well as the understanding that frequency varied over different periods might have been caused by an extreme process deep inside Earth. While researchers can only theorise what is going on inside our planet, blocks of millions of years without significant changes are thought to be caused by the decrease in the heat exchange between the core and mantle.
The times of relative serenity are believed to be changed by periods of intense reversing, like the one around 550 million years ago when the field flip-flopped 24 times every million years. The end of this turbulent period was marked by the extinction catastrophe named the Kotlinian Crisis, which prompted some scientists to conclude that there is a link between the geological unrest and the drastic ecological changes.
The debates around what our geological future holds for us have been a hot topic as scientists are trying to calculate when the magnetic field will flip next time and how it will happen. The last time the poles swapped places was about 780,000 years ago while the complete reversal is said to have taken place every few hundred millennia over the past 20 million years. Even though the imminent reversal is not expected, the question of what drifting poles might cause is still open with risks including its influence on all sorts of devices and high doses of radiation.