Geology

Magnetic Perseverance

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Science  16 Jan 2009:
Vol. 323, Issue 5912, pp. 310
DOI: 10.1126/science.323.5912.310c

Earth currently has a strong magnetic field generated from fluid motion in its outer core, thought to be driven by heat released from the solidification of its inner core. This field (depicted graphically above) helps shield Earth from harmful cosmic rays. The timing of the formation of the inner core and the nature of the field in the Archean (before 2.7 billion years ago) are debated but important for understanding the origin and early evolution of life. Selkin et al. were able to obtain more than 100 paleointensity measurements from the Stillwater layered intrusion, a large late Archean magma reservoir in Montana. The data imply that Earth's field then was as strong as it is today. Considering these data with the albeit sparse other Archean data, there is no clear indication that the field's strength has decreased or increased greatly over time. — BH

Geochem. Geophys. Geosyst. 9, Q12023 (2008).

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