The Earth’s magnetic field, which shields our planet from cosmic radiation, might be substantially governed by two massive hot zones situated at the boundary separating the core and the mantle. This conclusion was reached by geophysicists who investigated the correlation between the planet’s deep structure and the magnetic field’s behavior over hundreds of millions of years, as reported by The Conversation portal.
The scientists clarified that the movement of molten iron within the Earth’s outer core generates the geodynamo—the mechanism responsible for creating the global magnetic field. Stable operation of this mechanism necessitates continuous cooling of the core. However, the researchers focused on two anomalous regions within the lower mantle—beneath Africa and the Pacific Ocean—where seismic waves travel at a slower pace, which signals a higher temperature.
The study’s authors observed that these regions are likely considerably warmer than the surrounding mantle material and exert a significant influence on the heat flow emanating from the core. They examined the magnetization preserved in ancient volcanic rocks dating back as far as 250 million years. It was discovered that the magnetic field’s orientation in these rocks was dependent not only on latitude but also on the longitude where they formed, particularly in equatorial zones. This observation does not align well with the traditional model but is readily accounted for by the influence of these hot areas.
To validate their hypothesis, the researchers employed computer simulations of the geodynamo. These simulations demonstrated that when heat escapes from the core unevenly—more slowly in the anomalous zones—the magnetic field becomes more stable and develops longitudinal variations that match the geological evidence.
In the authors’ view, these hot spots function as thermal insulators, impeding the cooling of the liquid metal underneath them. This suppresses the churning motion of matter in the outer core while simultaneously shielding the magnetic field. The researchers concluded that these deep structures apparently contribute to the long-term stability of Earth’s magnetic field across geological timescales.
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