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Science 24 April 2009:
Vol. 324. no. 5926, pp. 474 - 476
DOI: 10.1126/science.1172879
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Perspectives

Geophysics:

The Thickness of Tectonic Plates

Barbara Romanowicz

A fundamental premise of plate tectonics on Earth is that rigid lithospheric plates, formed at mid-ocean ridges, float above a more deformable substratum, the asthenosphere (1). The precise nature of the asthenosphere is still debated. Mechanical models predict a well-defined, sharp lithosphere-asthenosphere boundary (LAB), but evidence for such a boundary from conventional seismic measurements is ambiguous. On pages 499 and 495 of this issue, Kawakatsu et al. (2) and Rychert and Shearer (3) present analyses of more sophisticated seismic studies that help refine the LAB and hence the thickness of the lithosphere and tectonic plates, although challenges still remain in picking out this boundary versus other structures within the lithosphere.

Berkeley Seismological Laboratory and Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, CA 94720, USA.

E-mail: barbara{at}seismo.berkeley.edu

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