Deep mantle structure and the postperovskite phase transition

Creators: Helmberger, D.; Lay, T.; Ni, S.; Gurnis, M.

Abstract

Seismologists have known for many years that the lowermost mantle of the Earth is complex. Models based on observed seismic phases sampling this region include relatively sharp horizontal discontinuities with strong zones of anisotropy, nearly vertical contrasts in structure, and small pockets of ultralow velocity zones (ULVZs). This diversity of structures is beginning to be understood in terms of geodynamics and mineral physics, with dense partial melts causing the ULVZs and a postperovskite solid–solid phase transition producing regional layering, with the possibility of large-scale variations in chemistry. This strong heterogeneity has significant implications on heat transport out of core, the evolution of the magnetic field, and magnetic field polarity reversals.

Additional Information

© 2005 by The National Academy of Sciences of the USA Edited by Russell J. Hemley, Carnegie Institution of Washington, Washington, DC, and approved August 22, 2005 (received for review March 28, 2005) Published online before print October 10, 2005, 10.1073/pnas.0502504102 Inaugural Article. D.H. was elected to the National Academy of Sciences in 2004. This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected on April 20, 2004. This paper was submitted directly (Track II) to the PNAS office. This work was supported by Cooperative Studies of the Earth's Deep Interior–National Science Foundation Grant Program EAR-0215644.

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