Stable regions in the Earth's liquid core

Summary. Slow cooling of the whole Earth can be responsible for the convection in the core that is required to generate the magnetic field. Previous studies have assumed the cooling rate to be high enough for the whole core to convect. Here we study the effects of a low rate of cooling by assuming the temperature at the base of the mantle to remain constant with an initially entirely molten, adiabatic core. We argue that, in such a situation, convection would stop at the top of the core, and calculate the consequent thermal evolution. A stable, density stratified layer grows downwards from the core mantle boundary reaching a thickness of 100-1000 km in a few thousands of millions of years. There is some geomagnetic evidence to support belief in the existence of such a stable layer.

[1]  Guy Masters,et al.  Observational constraints on the chemical and thermal structure of the Earth's deep interior , 1979 .

[2]  S. I. Braginskiy.  Magnetic Waves in the Earth's Core , 1967 .

[3]  D. Gubbins.  Speculations on the origin of the magnetic field of Mercury , 1977 .

[4]  W. Peltier,et al.  Parameterized mantle convection and the Earth's thermal history , 1978 .

[5]  S. Jacobsen,et al.  The Mean Age of Mantle and Crustal Reservoirs for the Planet Mars , 1979 .

[6]  P. Hamilton,et al.  Geochemical modeling of mantle differentiation and crustal growth , 1979 .

[7]  G. Kennedy,et al.  The adiabatic gradient and the melting point gradient in the core of the Earth , 1971 .

[8]  G. Müller,et al.  Changes in dimensions, stresses and gravitational energy of the Earth due to crystallization at the inner-core boundary under isochemical conditions , 1979 .

[9]  D. Gubbins.  Energetics of the Earth's core. , 1977 .

[10]  D. L. Anderson,et al.  Core formation, evolution, and convection - A geophysical model , 1980 .

[11]  J. Turner,et al.  Buoyancy Effects in Fluids , 1973 .

[12]  J. Verhoogen.  Energetics of the Earth , 1980 .

[13]  K. Whaler,et al.  Does the whole of the Earth's core convect? , 1980, Nature.

[14]  D. Loper,et al.  Compositional convection and stratification of Earth's core , 1981, Nature.

[15]  D. Gubbins,et al.  Generation of magnetic fields by fluid motions of global scale , 1977 .

[16]  J. Verhoogen.  Heat Balance of the Earth's Core , 1937 .

[17]  Adam M. Dziewonski,et al.  Parametrically simple earth models consistent with geophysical data , 1975 .

[18]  R. Hide.  On hydromagnetic waves in a stratified rotating incompressible fluid , 1969, Journal of Fluid Mechanics.

[19]  Raymond Hide,et al.  Free hydromagnetic oscillations of the earth's core and the theory of the geomagnetic secular variation , 1966, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[20]  F. Lowes,et al.  The analysis of the geomagnetic secular variation , 1951, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[21]  P. Molnar,et al.  Distribution of stresses in the descending lithosphere from a global survey of focal‐mechanism solutions of mantle earthquakes , 1971 .

[22]  W. Peltier,et al.  A thermal history model for the Earth with parameterized convection , 1979 .

[23]  D. Tozer.  The present thermal state of the terrestrial planets , 1972 .

[24]  Donald L. Turcotte,et al.  On the thermal evolution of the earth , 1980 .

[25]  D. Loper.  The gravitationally powered dynamo , 1978 .

[26]  D. Gubbins,et al.  Thermal evolution of the Earth's core , 1979 .

[27]  F. Richter,et al.  Parameterized thermal convection in a layered region and the thermal history of the Earth , 1981 .

[28]  G. Schubert,et al.  Subsolidus convective cooling histories of terrestrial planets , 1979 .

[29]  J. A. Jacobs,et al.  The Earth's Inner Core , 1953, Nature.

[30]  G. Davies.  Thermal histories of convective Earth models and constraints on radiogenic heat production in the Earth , 1980 .

[31]  D. W. Allan,et al.  The Thermal History of the Earth , 1956, Nature.

[32]  D. Gubbins.  Observational constraints on the generation process of the earth's magnetic field. , 1976 .