Studies of seismic tomography and reconstruction of supercontinents Rodinia and Pangea indicate that the Earth's mantle convection is predominated at very long wavelengths at least in the last 1 Ga. Recent studies on paleomagnetism also suggest possible true polar wander (TPW) events associated with Rodinia supercontinent. However, neither the formation process for long-wavelength platforms of mantle convection nor supercontinent process is well understood. The proposed work seeks to understand the underlying physics for long-wavelength platforms of mantle convection and its relation to supercontinent processes including TPW. We propose to formulate 3-D spherical mantle convection models with realistic rheology and with multiple continental blocks to determine the controls on long-wavelength platforms of mantle convection and cyclic processes of assembly and breakup of supercontinents. This research will support a PhD level graduate student, and includes international collaboration with Dr. Z-X. Li from University of Western Australia.