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The Mantle Flow Field Beneath Western North America

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Science  08 Feb 2002:
Vol. 295, Issue 5557, pp. 1054-1057
DOI: 10.1126/science.1066878

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Abstract

Although motions at the surface of tectonic plates are well determined, the accompanying horizontal mantle flow is not. We have combined observations of surface deformation and upper mantle seismic anisotropy to estimate this flow field for western North America. We find that the mantle velocity is 5.5 ± 1.5 centimeters per year due east in a hot spot reference frame, nearly opposite to the direction of North American plate motion (west-southwest). The flow is only weakly coupled to the motion of the surface plate, producing a small drag force. This flow field is probably due to heterogeneity in mantle density associated with the former Farallon oceanic plate beneath North America.

  • * To whom correspondence should be addressed. E-mail: silver{at}dtm.ciw.edu

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