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Earth’s Core

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Encyclopedia of Geochemistry

Part of the book series: Encyclopedia of Earth Sciences Series ((EESS))

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Definition

The composition of the Earth’s core is essentially 85% Fe, 5% Ni, and ~10% other, by weight. The details are more complicated, with the “other” being a light element component, which results in the core having on average a lower mean atomic number than that of iron. Birch (1952, 1964) recognized a 10% difference in the density of the outer core relative to an iron-nickel alloy at core pressure and temperature conditions. Anderson and Isaak (2002) recommend that the core density deficit is between 3% and 7%. Both the liquid outer core (~95% by mass) and solid inner core (~5%) contain a fraction of a light element (nominally in a ~2/1 proportion, respectively).

Properties

For more than a century the Earth has been described as having a metallic core surrounded by a silicate shell. A brief history of this topic is given in McDonough (2014). Emil Wiechert in 1897 first subdivided the Earth’s interior into these two main components and later, his graduate student Beno Gutenberg,...

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Authors and Affiliations

  1. Department of Geology, University of Maryland, College Park, MD, USA

    William F. McDonough

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  1. William F. McDonough
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Correspondence to William F. McDonough .

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  1. Cornell University, Ithaca, NY, USA

    William M. White

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McDonough, W.F. (2018). Earth’s Core. In: White, W.M. (eds) Encyclopedia of Geochemistry. Encyclopedia of Earth Sciences Series. Springer, Cham. https://doi.org/10.1007/978-3-319-39312-4_258

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