HR: 0800h
AN: P51B-0931    [Abstracts]
TI: Towards a Power Balance for Earth's Interior
AU: * Anderson, O L
EM: ola@ess.ucla.edu
AF: Institute of Geophysics and Planetary Physics and Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles E. Young Dr. E, Los Angeles, CA 90095-1567 United States
AB: The purpose of this presentation is to enumerate and describe the major power mechanisms and find a power balance for Earth's interior that compares favorably with a well-accepted measured value. The power leaving Earth's interior is the total power produced by sources (such as radiogenic activity) modified by the total power of passive mechanisms (such as plumes) that transfer power from one part of Earth to another. There are five power sources: (1)~The radiogenic power of Earth, found to be 31.2~TW (2.1~TW in the core and 8.2~TW in the continental crust); (2)~gravity release due to thermal contraction as the temperature declines; (3)~internal friction due to mantle convection; (4)~heat of crystallization released as the inner core grows; (5)~power associated with convection arising as fractionation proceeds on the ICB boundary. Several passive transport mechanisms convey power from one site to another in Earth by means of a negative thermal gradient dT/dr, where r is the radius measured to the center. The value of heat flux flowing outward is controlled by the Fourier law of conductive heat flow or by conductive heat flow (found in D^'', the mantle, the lithosphere, and the outer core). Convective heat flow is found in plumes and hydrothermal cooling of the lithosphere. In the circulating system of mantle convection, some mechanisms have a compensating negative counterpart. An example is the melting of the mantle to produce liquid basalt at the ridge axis, which requires energy. But subsequent solidification cancels the effect of melting in the power budget because it releases the same energy. Our analysis consists of finding and evaluating sources and transfer mechanisms. The net power leaving the system is found to be 40.2± 5 TW, in substantial agreement with the value of Pollack et al. (1993), who reported the average heat flow leaving Earth as 87 ± 2.0m̅W m^-2 (or 44.2 ± 1 TW).
DE: 5418 Heat flow
DE: 5430 Interiors (8147)
DE: 8147 Planetary interiors (5430, 5724, 6024)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005