Effect of the Crust on the Mantle Convection

Thermal coupling of the crust and the mantle is examined for a mantle convection of Pekeris-type. Thermally stable stage (no horizontal temperature gradient) is given as an initial condition for the mantle laid under the continental crust. In the meantime, this state is disturbed by the high radioactivity and the low thermal conductivity of the crust. Convection current is generated under the central part of the continental crust at about 108 years after start. Even if an initial pattern directed from ocean toward continent is existed within the mantle, a counter current from continent toward ocean develops under the continent within a time range of 108 years.It is concluded that the mantle convection is strongly affected by the thermal properties of the crust within a geologic time scale.