We consider two-dimensional convective motion of a Boussinesq fluid as shown in Figure 2. The model domain has horizontal and vertical dimensions of 12 and 1, respectively. A continental plate is represented by a rectangular zero-velocity region near the upper surface. Within the plate, heat is transported by conduction only. This region is not displaced by convective flow in the fluid layer. The model incorporates no internal heat sources, and the thermal diffusivity and viscosity are constant throughout. The temperatures at the top and bottom boundaries are fixed and the fluid is cooled from the top and heated from the bottom.

Figure 2: A schematic picture of the model