HR: 0830h
AN: U51B-0013    [PDF]
TI: Thermal histories of earth models as constrained by the present-day heat flux across the core-mantle boundary
AU: * Kuo, B
EM: byk@earth.sinica.edu.tw
AF: Institute of Earth Sciences,Academia Sinica, POB 1-55 Nankang, Taipei, 12345 Taiwan
AU: Cheng-Chien, P
EM: searchforhome@yahoo.com.tw
AF: Department of Geosciences, National Taiwan University, #1 Roosevelt Road section 4, Taipei, 12345 Taiwan
AU: Hsin-Ying, Y
EM: ysinging@earth.sinica.edu.tw
AF: Department of Geosciences, National Taiwan University, #1 Roosevelt Road section 4, Taipei, 12345 Taiwan
AB: The overall way Earth releases heat by convection can be parameterized into a relation between the Nusselt number and the Rayleigh number to the power of beta. The parameter beta for isoviscous convection is approximately 0.3. For Earth, there have been arguments in favor of a much lower beta, or even a negative one, on the ground that such models avoid ­thermal catastrophe­" in the early time of the planet. We follow the common procedure in the study of the thermal history of Earth in that we search for acceptable models by testing different initial temperatures and let the model ­cools­" until the present-day constraints are satisfied. These constraints include core-mantle boundary temperature, temperature at 660 km, surface heat loss by mantle convection, and viscosities in lithosphere, mid-mantle, and lower mantle. In this study, a constraint on the core heat flux is introduced, which is assumed to be 3-10 TW. We found that, with different degrees of layering in the mid-mantle, a beta of 0.3 yields acceptable models with a set of reasonable initial temperatures (no catastrophe). Smaller beta on the contrary cannot lead to an earth-like present-day status as described above. If the thermal boundary layer at the core-mantle boundary is eliminated from the model, i.e., the core heat flux is assumed adiabatic, no acceptable solutions have been reached. We are carrying out seismological effort to nail down the present-day core heat flux and will also examine the effect of radiogenic heating in the core.
DE: 7203 Body wave propagation
DE: 8115 Core processes (1507)
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8125 Evolution of the Earth
SC: U
MN: 2003 Fall Meeting