New research suggests that ancient magnetic field was generated from several poles rather than the familiar two.
Earth's magnetic field is a shield that deflects high energy particles and protects humans from harmful cosmic radiations. Without it, life as we know could not exist on Earth’s surface.
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The structure of Earth’s magnetic field is similar to that of a bar magnet that extends from two poles and encircles the whole object. But our planet’s magnetic field was not always like this. New research suggests that ancient magnetic field was considerably different from the present-day field as it was originated from several poles instead of conventional two.
Earth’s magnetic field is generated deep down in the outer core with the motion of liquid iron inside it. The phenomenon is called geodynamo and is driven by the constant loss of heat from the inner core. But since the inner core of Earth was not solid initially, it would have a different kind of effect on magnetic field. This is what researchers tried to find out in the latest study.
After thorough analysis of ancient rocks, scientists have already been able to work out the likely structure of Earth’s magnetic field but this structure has flaws. The data obtained from ancient rocks doesn’t show much evidence for major changes in the intensity of the ancient magnetic field over the past 4 billion years.
In order to address this issue, Peter Driscoll a researcher from Carnegie Institution for Science modeled the planet’s thermal history since its formation around 4.6 billion years ago and found that the inner core should have begun to solidify around 650 billion years ago. Based on 3D simulations of geodynamos created by turbulent liquid motions and models of Earth’s thermal history, researcher was able to look at the expected changes in the magnetic field over this period.
Results showed that Earth’s magnetic field had gone through a major transformation from strong magnetic field with two opposite poles in the north and south of the planet from weak magnetic fields generated from several poles around 1 billion years ago. The process reversed when inner core solidification took place millions of years ago.
"What I found was a surprising amount of variability. These new models do not support the assumption of a stable dipole field at all times, contrary to what we'd previously believed,” said Driscoll.
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“These findings could offer an explanation for the bizarre fluctuations in magnetic field direction seen in the geologic record around 600 to 700 million years ago. And there are widespread implications for such dramatic field changes.”