Mantle Dynamics: Grain Size Does Matter

Monday, March 18, 2002 - 10:30am - 11:30am
Keller 3-180
Slava Solomatov (New Mexico State University)
The lack of anisotropy in the lower mantle of the Earth suggests that deformation is controlled by diffusion creep or superplasticity. This implies that the viscosity depends on the grain size. Analysis of various kinetic processes in the Earth's mantle suggests that the grain size is mainly controlled by Ostwald ripening of Mg-perovskite, Ca-perovskite and magnesiowustite. The coupling between Ostwald ripening, viscosity and convection strongly affects thermal evolution of the Earth. Depending on the grain growth parameters, the Earth can either quickly forget the initial conditions with temperature and heat loss following the decaying radiogenic heat production (Tozer-type evolution) or the initial conditions can essentially determine the temperature and heat loss (Christensen-type evolution).