HR: 09:35h
AN: S11A-06 INVITED     [PDF]
TI: Thermal evolution of the Earth, plate tectonics, and chemical geodynamics
AU: * Korenaga, J
EM: jun.korenaga@yale.edu
AF: Department of Geology and Geophysics, Yale University, PO Box 208109, New Haven, CT 06520 United States
AB: A heat-flow scaling law for mantle convection has been playing a fundamental role in modeling the thermal evolution of the Earth. The sensitivity of surface heat flux to a change in mantle temperature is usually considered to be positive; the Archean Earth is characterized by hotter mantle, more vigorous plate tectonics, and thus higher heat flow. This positive sensitivity is surprisingly robust - isoviscous convection, stagnant-lid convection, and plate-tectonic convection all show essentially the same positive sensitivity. The generation of oceanic plate at mid-ocean ridges, however, involves decompressional mantle melting, which have a strong influence on the subsequent evolution of the top boundary layer in mantle convection. Global energetics of mantle convection, incorporating this interaction between chemical differentiation and mantle dynamics, exhibits an inverse relationship between mantle temperature and surface heat flux. This suggests that plate tectonics may have been more sluggish in the past than present. The new heat-flow scaling law has a number of intriguing implications for the heat budget of the Earth, the style of mantle convection, the thermal history of the core, and the chemical evolution of the Earth. Critical issues relevant to future research directions will be discussed.
DE: 1010 Chemical evolution
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8125 Evolution of the Earth
DE: 8130 Heat generation and transport
SC: Seismology [S]
MN: 2003 Fall Meeting