Earth’s magnetic field had the lowest tensions around 565 million years ago, when its powerful dynamo was on the verge of extinction. Since the formation of the solid inner core of the Earth would strengthen the geomagnetic field, this indicates that by that time the inner core was not yet solidified.
The estimate of the period of formation of a solid core varies widely – from 2.5 billion to 500 million years ago. However, these time parameters can be refined by analyzing the stony rocks that store traces of the ancient nature of the geomagnetic field. The solidification of liquid iron at the fragile boundary of the inner core would become an important source of energy for geodynamo – convection flows of the liquid metal in the outer core, which feed the magnetic field. Based on computer simulations, scientists determined that such an increase in energy would be historically “documented” in the rock following the tracks of the geomagnetic field intensity.
John Tarduno of the University of Rochester (USA) and his colleagues measured the ancient intensity and direction of the geomagnetic field recorded in tiny magnetic inclusions found in plagioclase and clinopyroxene single crystals that formed 565 million years ago in the area currently serving as the eastern part of Quebec in Canada . They revealed an unprecedented low intensity of the geomagnetic field, and also concluded that at this time there was a high frequency of magnetic inversions. The discovery led them to conclude that the geodynamo was on the verge of collapse.
It seems that the nucleation of the inner core happened just in time to recharge the geodynamo and save the Earth’s magnetic shield.
-Peter Driscoll, co-author of the study at Carnegie University (USA)
Earth’s magnetic field was on the verge of extinction
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