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Science 21 January 1966:
Vol. 151. no. 3708, pp. 321 - 322
DOI: 10.1126/science.151.3708.321
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Articles

Earth's Viscosity

Don L. Anderson 1

1 Seismological Laboratory, Division of Geological Sciences, California Institute of Technology, Pasadena

Seismic methods are now being used to determine not only Earth's elastic properties, but also by how much it departs from a perfectlyelastic body. The seismic anelasticity (Q) varies by several orders of magnitude throughout the mantle, the main feature being an extremely dissipative zone in the upper mantle above 400 kilometers. Recent determinations of viscosity by McConnell show a similar trend. The two sets of data indicate that the ratio of viscosity to Q is roughly a constant, at least in the upper mantle of Earth. On the assumption that this relation is valid for the rest of Earth, viscosities are estimated in regions that are inaccessible for direct measurement. The implied presence of a low-viscosity zone in the upper mantle, overlying a more viscous, less deformable, lower mantle, reconciles viscosites calculated from the shape of Earth and from postglacial uplift. The mismatch of the deformational characteristics at various levels in Earth, coupled with the changing rate of rotation, may be pertinent to the rate of release of seismic energy as a function of depth.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
The Upper Mantle of the Earth.
L. Knopoff and L. Knopoff (1969)
Science 163, 1277-1287
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