HR: 16:05h
AN: NG14A-01 INVITED     [Abstracts]
TI: The Surface Area of Continents and Oceans and the Cooling of the Earth
AU: * Lenardic, A
EM: adrian@esci.rice.edu
AF: Rice University, Department of Earth Science. MS 126, P.O. Box 1892, Houston, TX 77251 United States
AU: Moresi, L
EM: louis.moresi@monash.edu
AF: Monash University, School of Mathematical Sciences, Building 8, Victoria, 3800 Australia
AU: Jellinek, A
EM: mjellinek@eos.ubc.ca
AF: The University of British Columbia, Department of Earth and Ocean Science, Vancouver, BC V6T1Z4 Canada
AU: Manga, M
EM: manga@seismo.berkeley.edu
AF: University of California, Department of Earth and Planetary Science, 307 McCone Hall, MC 4767, Berkeley, CA 94720 United States
AU: Cooper, C M
EM: cmcooper@rice.edu
AF: Rice University, Department of Earth Science. MS 126, P.O. Box 1892, Houston, TX 77251 United States
AB: The solid Earth looses it internal heat principally through convection. The oceanic lithosphere is the active upper thermal boundary layer of mantle convection and its overturn is critical to the Earth's mode of heat loss. Long lived, conducting continents at the Earth's surface locally insulate the convecting mantle and thus also effect global cooling rate. We explore the dynamics of this conjugated heat transfer system using simple analogs that incorporate conducting layers of finite depth and extent above a convecting material with strongly temperature dependent rheology. Theory, experiments, and numerical simulations all show that there is a surface area of insulating material that maximizes global heat flow. Partial insulation leads to increased internal mantle temperature and decreased mantle 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 also increase as a result. An added complexity is that continental insulation, through its effect on mantle viscosity, also effects convective stresses. Depending on the yield stress of the lithosphere and the area of continents, this can cause a transition from an active lid mode of convection, in which oceanic lithosphere overturns, to stagnant lid mode. This added complexity shifts the parameter combinations that predict optimal cooling. These parameter combinations are compared to observed values, in particular the surface area of continents, to asses whether the theoretical prediction of an optimal state is an interesting fluid dynamical novelty or whether it may apply to the Earth.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8130 Heat generation and transport
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005