Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 13 January 2006:
Vol. 311. no. 5758, pp. 198 - 201
DOI: 10.1126/science.1120020
Prev | Table of Contents | Next

Reports

The Nature of the 660-Kilometer Discontinuity in Earth's Mantle from Global Seismic Observations of PP Precursors

Arwen Deuss,1* Simon A. T. Redfern,1 Kit Chambers,2 John H. Woodhouse2

The 660-kilometer discontinuity, which separates Earth's upper and lower mantle, has been detected routinely on a global scale in underside reflections of precursors to SS shear waves. Here, we report observations of this discontinuity in many different regions, using precursors to compressional PP waves. The apparent absence of such precursors in previous studies had posed major problems for models of mantle composition. We find a complicated structure, showing single and double reflections ranging in depth from 640 to 720 kilometers, that requires the existence of multiple phase transitions at the base of the transition zone. The results are consistent with a pyrolite mantle composition.

1 Department of Earth Sciences, University of Cambridge, Cambridge CB3 0EZ, UK.
2 Department of Earth Sciences, University of Oxford, Oxford OX1 3PR, UK.

* To whom correspondence should be addressed. E-mail: deuss{at}esc.cam.ac.uk.

Read the Full Text


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
The Upper Mantle and Transition Zone.
D. J. Frost (2008)
Elements 4, 171-176
   Abstract »    Full Text »    PDF »
Splitting of the 520-Kilometer Seismic Discontinuity and Chemical Heterogeneity in the Mantle.
A. Saikia, D. J. Frost, and D. C. Rubie (2008)
Science 319, 1515-1518
   Abstract »    Full Text »    PDF »
Upper Mantle Discontinuity Topography from Thermal and Chemical Heterogeneity.
N. Schmerr and E. J. Garnero (2007)
Science 318, 623-626
   Abstract »    Full Text »    PDF »
The eclogite engine: Chemical geodynamics as a Galileo thermometer.
D. L. Anderson (2007)
Geological Society of America Special Papers 430, 47-64
   Abstract »    Full Text »    PDF »
The structure of thermal plumes and geophysical observations.
S. D. King and H. L. Redmond (2007)
Geological Society of America Special Papers 430, 103-120
   Abstract »    Full Text »    PDF »
Seismic observations of transition-zone discontinuities beneath hotspot locations.
A. Deuss (2007)
Geological Society of America Special Papers 430, 121-136
   Abstract »    Full Text »    PDF »


To Advertise     Find Products

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