Publication Date:
2006-01-18
Description:
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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Deuss, Arwen -- Redfern, Simon A T -- Chambers, Kit -- Woodhouse, John H -- New York, N.Y. -- Science. 2006 Jan 13;311(5758):198-201.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of Cambridge, Cambridge CB3 0EZ, UK. deuss@esc.cam.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16410518" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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