Electrical Conductivity of Post-Perovskite in Earth's D'' Layer

• Published in: Science (American Association for the Advancement of Science) Vol. 320; no. 5872; pp. 89 - 91
• Main Authors: Ohta, Kenji, Onoda, Suzue, Hirose, Kei, Sinmyo, Ryosuke, Shimizu, Katsuya, Sata, Nagayoshi, Ohishi, Yasuo, Yasuhara, Akira
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 04-04-2008; The American Association for the Advancement of Science
• Subjects: Chemistry; Conductivity; Core mantle boundary; Crystalline rocks; D layer; Earth; Earth sciences; Earth, ocean, space; Electrical phases; Electrical resistivity; Electrodes; Electromagnetism; Exact sciences and technology; Experimental petrology; Geophysics; High temperature; Internal geophysics; Mantle; Perovskites; Solid-earth geophysics, tectonophysics, gravimetry; experimental studies; physical properties; perovskite; oxides; lower mantle; phase transitions; electromagnetic properties; core-mantle boundary; high temperature; heterogeneity; coupling; transition zones; instruments; diamond anvil cells; electrical conductivity
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1155148

Recent discovery of a phase transition from perovskite to post-perovskite suggests that the physical properties of Earth's lowermost mantle, called the D'' layer, may be different from those of the overlying mantle. We report that the electrical conductivity of (Mg₀.₉Fe₀.₁)SiO₃ post-perovskite is >10² siemens per meter and does not vary greatly with temperature at the conditions of the D'' layer. A post-perovskite layer above the core-mantle boundary would, by electromagnetic coupling, enhance the exchange of angular momentum between the fluid core and the solid mantle, which can explain the observed changes in the length of a day on decadal time scales. Heterogeneity in the conductivity of the lowermost mantle is likely to depend on changes in chemistry of the boundary region, not fluctuations in temperature.