50 years ago, scientists named Earth’s magnetic field as a suspect in extinctions

Excerpt from the November 21, 1970 issue of Science News

a microscopic image showing several radiolarians

In 1970, researchers linked the extinction of several species of tiny marine organisms called radiolarians (10 living species pictured here) with reversals in the direction of Earth’s magnetic field.

Randolph Femmer/USGS

cover of the November 21, 1970 issue

Effects of Earth’s magnetic field Science News, November 21, 1970

Earth’s magnetic field has frequently reversed at intervals of 1 million to 100 million years. A few scientists now suspect that these reversals may have had drastic effects on terrestrial life.… During the past 2.5 million years, eight species of one-cell marine animals called Radiolaria became extinct. Six of these extinctions occurred simultaneously throughout their geographic range immediately following magnetic reversals.


Earth’s magnetic field protects the planet from cosmic and solar radiation, but that field can weaken during pole reversals. Such reversals might harm more than select species, perhaps playing a role in some mass extinctions. Direct evidence has eluded researchers, but there are suggestive examples. In 2016, scientists linked a mass extinction of marine life 550 million years ago with reversals that weakened the magnetic field. The resulting increased radiation could have led to the demise of many shallow-water organisms, the team speculated.

Jonathan Lambert is a former staff writer for biological sciences, covering everything from the origin of species to microbial ecology. He has a master’s degree in evolutionary biology from Cornell University.

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