HR: 11:20h
AN: T42A-05    [Abstracts]
TI: Continental Insulation, Mantle Cooling, and the Surface Area of Oceans and Continents
AU: * Lenardic, A
EM: adrian@geophysics.rice.edu
AF: Rice University, Department of Earth Science, P.O. Box 1892, Rice University, Houston, TX 77251 United States
AU: Moresi, L
EM: louis.moresi@sci.monash.edu
AF: Monash University, School of Mathematical Sciences, Building 28, Monash University, Victoria, 3800 Australia
AU: Jellinek, A M
EM: markj@physics.utoronto.ca
AF: University of Toronto, Department of Physics, 60 St. George St., University of Toronto, Toronto, Ont M5S 1A7 Canada
AU: Manga, M
EM: manga@seismo.berkeley.edu
AF: University of California, Department of Earth and Planetary Science, 307 McCone Hall, MC 4767, University of California, Berkeley, CA 94720 United States
AB: It is generally assumed that continents, acting as thermal insulation above the convecting mantle, inhibit the Earth's internal heat loss. We present theory, numerical simulations, and laboratory experiments to test the validity of this intuitive and commonly used assumption. A scaling theory is developed to predict heat flow from a convecting mantle partially covered by stable continental lithosphere. The theory predicts that parameter regimes exist for which increased continental insulation has no effect on mantle heat flow and can even enhance it. Partial insulation leads to increased internal mantle temperature and decreased viscosity. This, in turn, allows for the more rapid overturn of oceanic lithosphere and increased oceanic heat flux. Depending on the ratio of continental to oceanic surface area, global mantle heat flow can remain constant or even increase as a result. Theoretical scaling analyses are consistent with results from numerical simulations and laboratory experiments. Applying our results to the Earth we find, in contrast to conventional understanding, that continental insulation does not generally reduce global heat flow. Such insulation can have a negligible effect or even enhance mantle cooling, depending on the magnitude of the temperature dependence of mantle viscosity. The implication of this result for the Earth's thermal evolution will be discussed.
DE: 8115 Core processes (1507)
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8125 Evolution of the Earth
DE: 8130 Heat generation and transport
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting