alloy
; cooling
; electrical conductivity
; freezing
; high pressure
; inner core
; iron
; lower mantle
; magnetic field
; oxygen
; partial melting
; silicon
; temperature effect
; thermal conductivity
; thermal evolution
; Calluna vulgaris
英文摘要:
The Earth's magnetic field is powered by energy supplied by the slow cooling and freezing of the liquid iron core. Efforts to determine the thermal and chemical history of the core have been hindered by poor knowledge of the properties of liquid iron alloys at the extreme pressures and temperatures that exist in the core. This obstacle is now being overcome by high-pressure experiments and advanced mineral physics computations. Using these approaches, updated transport properties for Fe-Si-O mixtures have been determined at core conditions, including electrical and thermal conductivities that are higher than previous estimates by a factor of two to three. Models of core evolution with these high conductivities suggest that the core is cooling much faster than previously thought. This implies that the solid inner core formed relatively recently (around half a billion years ago), and that early core temperatures were high enough to cause partial melting of the lowermost mantle. Estimates of core-mantle boundary heat flow suggest that the uppermost core is thermally stratified at the present day.
School of Earth and Environment, University of Leeds, Leeds, United Kingdom; Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, San Diego, CA, United States; Department of Earth Sciences, Thomas Young Centre at UCL, UCL, Gower Street, London, United Kingdom; Department of Physics and Astronomy, London Centre for Nanotechnology, UCL, Gower Street, London, United Kingdom
Recommended Citation:
Davies C.,Pozzo M.,Gubbins D.,et al. Constraints from material properties on the dynamics and evolution of Earth's core[J]. Nature Geoscience,2015-01-01,8(9)