Document Detail

Outer-core compositional stratification from observed core wave speed profiles.
MedLine Citation:
PMID:  21150995     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Light elements must be present in the nearly pure iron core of the Earth to match the remotely observed properties of the outer and inner cores. Crystallization of the inner core excludes light elements from the solid, concentrating them in liquid near the inner-core boundary that potentially rises and collects at the top of the core, and this may have a seismically observable signal. Here we present array-based observations of seismic waves sensitive to this part of the core whose wave speeds require there to be radial compositional variation in the topmost 300 km of the outer core. The velocity profile significantly departs from that of compression of a homogeneous liquid. Total light-element enrichment is up to five weight per cent at the top of the core if modelled in the Fe-O-S system. The stratification suggests the existence of a subadiabatic temperature gradient at the top of the outer core.
George Helffrich; Satoshi Kaneshima
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Nature     Volume:  468     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-12-14     Completed Date:  2011-01-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  807-10     Citation Subset:  -    
Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
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