According to a to a new study published in the scientific journal “Geophysical Research Letters”, the Earth may have had more than two magnetic poles in the past.
Planet Earth, as we know it today, has two magnetic poles, the south, and the north pole. The fact that we are surrounded by a magnetic field acts as a protection against solar radiation, which can cause harm. It is precisely for this reason that life is possible on our planet. Otherwise, radiation will burn everything, apart from the most persistent, heat-resistant microorganisms.
Without a magnetic field surrounding our planet, the solar winds would strip away the ozone layer, which protects us from harmful radiation.
According to the new study, the Earth may have had more than two magnetic poles around 800 million years ago. It was then when our planet might have developed a multipolar magnetic field.
It is believed that Earth magnetic field originates from its core. Nobody actually could tell for sure the origin of the geomagnetic field. However, after studying the way the shockwaves produced by earthquakes travel through the layers of our planet, scientists could determine its structure.
At its heart, the Earth has a solid core made of iron. Despite its high temperature (5700 degrees Celsius, which is similar to the temperature of the Sun`s surface), this metal is kept in a solid form and prevented to turn into liquid due to the massive gravitational forces.
This inner core is wrapped in an outer layer made of liquid iron and nickel. Since the gravitational forces are not as powerful here, the metal cannot be prevented to melt.
However, the temperature in the outer core of the Earth is not homogenous. Because its thickness is around 2,000 kilometers, there are continuous exchanges between the molten metals at the surface whose density and cold temperature make it sink and the warm and less dense matter, which raises.
Furthermore, we need to take into account the Coriolis force (the force resulted from the Earth`s spinning), which also creates swirling whirlpools.
Therefore, this permanent flow of liquid metal generates electric current, which in its turn produces magnetic fields. This continuous and self-sustaining movement is known under the name of geodynamo.
Nonetheless, according to the study, the inner core of our planet was not always solid. After analyzing the Earth`s thermal history, the scientists suggest that the inner core started to solidify only around 650 million years ago.
However, the prediction that Earth may have had more than two magnetic poles still needs to be confirmed by the investigation of magnetized rocks. So far, this theory was verified only through simulations, which still need to be checked.
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