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Thermal evolution of Earth with magnesium precipitation in the core

O'Rourke, Joseph G. and Korenaga, Jun and Stevenson, David J. (2017) Thermal evolution of Earth with magnesium precipitation in the core. Earth and Planetary Science Letters, 458 . pp. 263-272. ISSN 0012-821X. doi:10.1016/j.epsl.2016.10.057.

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Vigorous convection in Earth's core powers our global magnetic field, which has survived for over three billion years. In this study, we calculate the rate of entropy production available to drive the dynamo throughout geologic time using one-dimensional parameterizations of the evolution of Earth's core and mantle. To prevent a thermal catastrophe in models with realistic Urey ratios, we avoid the conventional scaling for plate tectonics in favor of one featuring reduced convective vigor for hotter mantle. We present multiple simulations that capture the effects of uncertainties in key parameters like the rheology of the lower mantle and the overall thermal budget. Simple scaling laws imply that the heat flow across the core/mantle boundary was elevated by less than a factor of two in the past relative to the present. Another process like the precipitation of magnesium-bearing minerals is therefore required to sustain convection prior to the nucleation of the inner core roughly one billion years ago, especially given the recent, upward revision to the thermal conductivity of the core. Simulations that include precipitation lack a dramatic increase in entropy production associated with the formation of the inner core, complicating attempts to determine its age using paleomagnetic measurements of field intensity. Because mantle dynamics impose strict limits on the amount of heat extracted from the core, we find that the addition of radioactive isotopes like potassium-40 implies less entropy production today and in the past. On terrestrial planets like Venus with more sluggish mantle convection, even precipitation of elements like magnesium may not sustain a dynamo if cooling rates are too slow.

Item Type:Article
Related URLs:
URLURL TypeDescription
O'Rourke, Joseph G.0000-0002-1180-996X
Korenaga, Jun0000-0002-4785-2273
Stevenson, David J.0000-0001-9432-7159
Additional Information:© 2016 Elsevier B.V. Received 7 June 2016; Received in revised form 14 September 2016; Accepted 27 October 2016; Available online 14 November 2016. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469. Thanks to John Hernlund, Jonathan Aurnou, and Roger Fu for helpful discussions. An anonymous reviewer provided many helpful comments that improved this manuscript.
Group:Astronomy Department
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Subject Keywords:Earth, interior; magnetic field; mantle convection; heat-flow scaling; thermal budget
Record Number:CaltechAUTHORS:20161121-081643081
Persistent URL:
Official Citation:Joseph G. O'Rourke, Jun Korenaga, David J. Stevenson, Thermal evolution of Earth with magnesium precipitation in the core, Earth and Planetary Science Letters, Volume 458, 15 January 2017, Pages 263-272, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72182
Deposited By: Tony Diaz
Deposited On:21 Nov 2016 19:39
Last Modified:11 Nov 2021 04:57

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