抄録
The effect of continental plates with large horizontal sizes on mantle convection is investigated by the use of a two-dimensional Boussinesq fluid model. A continental plate is realized as a rectangular zero-velocity region near the upper surface of the model domain with the aspect ratio of 12. Numerical results show that the convection cells extending over the regions below and outside the plate are horizontally elongated and upwellings exist below the center of the plate when Ra=105 and 106. However, in the case of Ra=104, the aspect ratio of the convection cell is nearly 1 and an upwelling exists below the margin of the plate.
By applying the boundary layer theory to the case of convection beneath the plate, the maximum horizontal size of the convection cell is predicted. It is shown that the convection cells with larger horizontal scale can emerge for the larger Rayleigh numbers, which is consistent with the results of numerical experiments.
The results suggest that an upwelling of the convection cell extending over the margin of a superontinent can be generated beneath the center of the continent in the case of whole mantle convection, however, in the case of upper mantle convection, an upwelling appears beneath its margin.
