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Science 2 March 2001:
Vol. 291. no. 5509, pp. 1714 - 1715
DOI: 10.1126/science.291.5509.1714
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Perspectives

GEOPHYSICS:
When the Compass Stopped Reversing Its Poles

Subir K. Banerjee

Earth's geomagnetic field normally reverses a few times every million years, but during "superchron" periods, this switching process may stop for 30 to 50 million years. In his Perspective, Banerjee highlights the study by Tarduno et al., who have deduced the paleomagnetic field strength during the Cretaceous superchron from magnetite inclusions in lavas found in India. The results may provide clues to what causes the superchron periods.

The author is at the Institute for Rock Magnetism, School of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA. E-mail: banerjee{at}umn.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)