image: Map showing present-day deviation from expected magnetic field direction. Blue colors show low deviation, yellow to red colors show high deviation. Star is Saint Helena location. The gray line indicates area on the core mantle boundary with low shear wave velocities. view more
Credit: Image credit: Yael Annemiek Engbers and Richard K. Bono.
A study suggests that an area of the South Atlantic Ocean has been subject to anomalous geomagnetic activity for millions of years. Liquid iron flowing in the Earth's core generates a magnetic field that protects the atmosphere from solar wind. In an area of the South Atlantic Ocean, the geomagnetic field is anomalous, a phenomenon that increases solar particles in the atmosphere, potentially hindering satellites. Yael Engbers and colleagues analyzed volcanic rocks on the South Atlantic island of Saint Helena, which was formed by two shield volcanoes, to determine whether the anomaly existed 8-11 million years ago. Because the basalt would reflect the orientation of the magnetic field at the time the lava cooled, the authors analyzed 225 core samples from 46 basalt flows on the island to determine the original magnetization direction of the samples. The results revealed variation in magnetic field directions higher than expected at the latitude. According to the authors, the results extend the persistence of anomalous activity from thousands to millions of years and support the idea that the anomaly is linked to interactions at the interface of the mantle and core.
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Article #20-01217: "Elevated paleomagnetic dispersion at Saint Helena suggests long-lived anomalous behavior in the South Atlantic," by Yael A. Engbers, Andrew J. Biggin, and Richard K. Bono.
MEDIA CONTACT: Yael Annemiek Engbers, University of Liverpool, UNITED KINGDOM; e-mail: y.a.engbers@liverpool.ac.uk; Andrew Biggin, University of Liverpool, UNITED KINGDOM; e-mail: biggin@liverpool.ac.uk
Journal
Proceedings of the National Academy of Sciences