Effects of core formation

Shaw, Geoge H.

doi:10.1016/0031-9201(78)90074-2

Cited by 29 publications

(7 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The inhomogeneous accretion hypothesis is also in agreement with isotopic abundance data, which indicate that the Earth's core formed early on in the history of the planet (Oversby and Ringwood, 1971; see also Shaw, 1978;Jacobs, 1970). It must be admitted though that such data can be interpreted in different ways; and while the core seems to have been formed early on (i.e., within 101-10 8 yr of the origin of the planet), this does not by itself necessarily imply that it originated in an inhomogeneous accretion process (Vollmer, 1977).…”

Section: Gravity Experimentssupporting

confidence: 80%

Gravity, Particles, and Astrophysics

Wesson¹

1980

Astrophysics and Space Science Library

View full text Add to dashboard Cite

Section: Gravity Experimentssupporting

confidence: 80%

Gravity, Particles, and Astrophysics

Wesson¹

1980

Astrophysics and Space Science Library

View full text Add to dashboard Cite

“…Suppose, first, that the planet starts out much hotter than its present temperature. This is likely for the earth, where early and rapid core formation may have produced a mantle temperature which was greater than the present value by 50-100% [Shaw, 1978]. In these circumstances, mantle convection is initially very vigorous, primarily because of the strong temperature dependence of the viscosity.…”

Section: The Modelsmentioning

confidence: 70%

Whole planet cooling and the radiogenic heat source contents of the Earth and Moon

Schubert¹,

Stevenson²,

Cassen³

1980

J. Geophys. Res.

255

187

View full text Add to dashboard Cite

It is widely believed that the surface heat ftows of the earth and moon provide good measures of the total amounts of radioactives in these bodies. Simple thermal evolution models, based on subsolidus whole mantle convection, indicate that this may not be the case. These models have been constructed assuming an initially h~t st~te, but with a wide varlet~ of choices for the parameters characterizing the rheology and convective vtgor. All models are constramed to be consistent with present-day surface heat ftux~s, and many of the terrestrial models are consistent with the mantle viscosities indicated by postglaCial rebound. For the earth the acceptable models give a radiogenic heat production that is only 65-85% o~the s~ace heat output, the ~erence being due to secular cooling of the earth (about 50°-l00°C ~r 10 years m the ~pper mantle). It IS argued that the actual heat generation may be substantially less, sm':l' t_he models omit core heat, upward migration of heat sources, possible layering of the mantle, and ~eVIations ~rom steady ~nvection. Geochemical models which are near to chondritic (apart from potas-51111:' 1 depletion) are marginally consistent with surface heat ftow. In the lunar models, heat generation is typ1cally only 70-80% of the surface heat ftow, even with allowance for the strong near-surface enhancement of radioactives. Despite the simplicity of the models the persistence of a significant difference between heat generation and heat output for a wide range of parameter choices indicates that this differ ence is real and should be incorporated in geochemical modeling of the planets. INTRODUCTIONAfter the discovery of radioactivity but before the widespread acceptance of mantle convection and plate tectonics, cooling of the earth was thought to contribute substantially to the geothermal heat fiux. Holmes [1916] attributed one quarter of the heat output to original heat, the rest being radiogenic, and Stichter [1941] stressed the large thermal inertia of the earth and the possibility of a large difference between heat generation and heat output.More recently, the acceptance of the idea that there are plate and mantle convective motions with time scales much less than the age of the earth has led to the view that there is essentially a steady state in which heat production and heat loss through the surface are almost balanced (Tozer, 1965;Turcotte and Oxburgh, 1972]. This assumption has been made in discussions of the thermal state of the moon [Runcorn, 1962] and in attempts to estimate the abundances of uranium, thorium, and potassium in the earth and moon [Langseth et a/., 1976].However, the 'steady state' assumption only implies that heat generated deep within the body can be transported to the surface in a time much smaller than the age of that body; it does not imply equality of heat generation and heat output. This can be demonstrated by the following contradiction. Suppose heat generation and heat output were always equal Since heat generation decreases with time because of the decay of...

show abstract

“…We assume that core formation occurred simultaneously with, or soon after, planetary accretion [Shaw, 1978;Solomon, 1979] and that the above described conditions in the mantle were also established early in the earth's thermal history. The subsequent thermal evolution of the earth is governed by heat balance equations for the mantle and core.…”

Section: Modelmentioning

confidence: 99%

Modes of mantle convection and the removal of heat from the Earth's interior

Spohn¹,

Schubert²

1982

J. Geophys. Res.

137

View full text Add to dashboard Cite

Earth thermal histories based on two‐layer and whole‐mantle parameterized convection models have been explored to determine the influence of the mode of mantle convection on the content and distribution of mantle radioactive heat sources and on the temperatures and heat transfer properties of the mantle. Two‐layer mantle convection thermally insulates the lower mantle and is less efficient at heat removal than whole mantle convection. Consequently, two‐layer mantle convection requires a lower mantle depleted of radioactive heat sources contrary to the undepleted lower mantles of recent geochemical models. Whole‐mantle convection removes 3 times more primordial heat from the earth's interior and 6 times more heat from the core in 4.5 billion years than does two‐layer convection. The average mantle volumetric heat generation rates for both modes of convection are comparable to that of a potassium‐depleted chondrite. Thus no potassium is necessary in the core to balance the observed present‐day surface heat flux. However, most of the radioactives are concentrated in the upper mantle for two‐layer convection. Model geotherms for whole‐mantle convection compare well with independent estimates of temperature at various depths, including the core‐mantle boundary, while the lower mantle is too hot for two‐layer convection models. Thermal histories of the upper mantle in two‐layer models are similar to those of whole mantle models. Thermal histories for the lower mantle in two‐layer models are similar to those of the core in whole mantle convection models. This is because the lower mantle is thermally insulated by the upper mantle if it convects separately, just as the core is thermally insulated by the whole mantle. The differences between whole and two‐layer mantle convection are mostly due to the thermal insulation of the lower mantle and the smaller efficiency of heat removal of the upper mantle compared to that of the whole mantle, which is much larger in volume. A whole‐mantle convection model reconciling the need for distinct geochemical reservoirs with the physics of mantle convection is presented.

show abstract

Effects of core formation

Cited by 29 publications

References 7 publications

Gravity, Particles, and Astrophysics

Gravity, Particles, and Astrophysics

Whole planet cooling and the radiogenic heat source contents of the Earth and Moon

Modes of mantle convection and the removal of heat from the Earth's interior

Contact Info

Product

Resources

About