In this activity, students construct a model that will allow them to experiment with thermal convection, illustrating how thermal energy can generate a flowing motion in a fluid. The thermal convection in this model is similar to the convection that is inferred for the Earth’s mantle and can produce horizontal flow that can cause or is related to plate motions. Students will investigate the viscosity of a fluid and find that the Earth’s mantle can be thought of as a solid for short duration processes (such as the propagation of seismic waves), and as a very viscous fluid for long duration processes (such as mantle convection and plate tectonic movements). Students will view the model several times during the experiment, both from above and from the side of the dish and draw a sketch of the circulation.