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Published January 19, 1992 | public
Journal Article

Plate Tectonics and Hotspots: The Third Dimension


High-resolution seismic tomographic models of the upper mantle provide powerful new constraints on theories of plate tectonics and hotspots. Midocean ridges have extremely low seismic velocities to a depth of 100 kilometers. These low velocities imply partial melting. At greater depths, low-velocity and high-velocity anomalies record, respectively, previous positions of migrating ridges and trenches. Extensional, rifting, and hotspot regions have deep (> 200 kilometers) low-velocity anomalies. The upper mantle is characterized by vast domains of high temperature rather than small regions surrounding hotspots; the asthenosphere is not homogeneous or isothermal. Extensive magmatism requires a combination of hot upper mantle and suitable lithospheric conditions. High-velocity regions of the upper 200 kilometers of the mantle correlate with Archean cratons.

Additional Information

© 2014 American Association for the Advancement of Science. We thank P. Molnar and W. Hamilton for useful reviews. This work was supported by the National Science Foundation. Contribution 5080, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.

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October 26, 2023