Researchers from the University of California, San Diego have published a new study that suggests that it wasn’t always the core of Earth that generated the magnetic field, instead, it could have been the mantle.
The study — Thermal and magnetic evolution of a crystallising basal magma ocean in Earth’s mantle — published in the journal Earth and Planetary Science Letters lends credence to the theory first proposed by a geophysicist at Scripps Institution of Oceanography at UC San Diego.
Mantle could have generated Earth’s magnetic field
The Earth has its own magnetic field that shields the planet from solar radiation. It also serves as the basis of navigation. The magnetic field has been believed to be the result of convection currents within the fluid of the planet’s outer core. However, the new study suggests that in the early days, it might have been the mantle that generated it.
The authors of the new study, Scripps Oceanography researchers Dave Stegman, Leah Ziegler, and Nicolas Blanc provide a “door-opening opportunity” to resolve inconsistencies in the narrative of the planet’s early days. The paper also coincides with two new studies from UCLA and Arizona State University geophysicists that expand on Stegman’s concept and apply it in new ways.
Problem with previous theory
In previous studies, Dave Stegman and Leah Ziegler had suggested that the mantle was not always completely solid. They suggested the existence of silicate-rich ‘basal magma ocean’ at th
e bottom of the mantle, in the early days of the Earth.
They claimed that this silicate-rich mantle could have produced Earth’s magnetic field at that point of time in the planet’s lifespan. However, this theory was not convincing as silicates are poor conductor of electricity and conductivity is important for convection currents that generate the magnetic field of the Earth.
Now, the trio of Stegman, Ziegler, and Blanc, gives a new estimate of the theory, which is also supported by two recently published studies.
Dynamo theory explains the way planets generate magnetic fields through convection currents. While one study focuses on the possibility of silicate dynamo in the mantle during the early days of Earth, the other study discusses the mechanism and lifespan of silicate ‘basal magma ocean’ on Venus.
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The study published in journal Nature says, “The Earth’s magnetic field may have transitioned from being produced by the basal magma ocean to being produced by the core near the end of the Archean”. It suggested that as oceans of magma cooled, the heat flowing out of the core increased and eventually led to the formation of the core dynamo.
JG O’Rourke, the author of the study published in the Geophysical Letters, explains in a statement to Scripps Institution of Oceanography, “Ultimately, our papers are complementary because they demonstrate that basal magma oceans are important to the evolution of terrestrial planets.”
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