Self-consistent generation of large aspect ratio oceanic plate and sublithospheric small-scale convection

How large aspect ratio oceanic plate was generated from mantle convection is a long standing question. In the thesis, I present mainly bottom heated, whole mantle convection results with temperature-dependent viscosity and focus on searching for the condition under which aspect ratio oceanic plate could be generated via plastic yielding. At the relatively high Rayleigh number and high viscosity contrast with the yielding stress at the order of 100 MPa, large aspect ratio oceanic plate could be generated with high quality of the plate. An asthenospheric viscosity reduction is not required to promote long wavelength convection. This suggests that a weak asthenosphere might not be a significant factor that leads to long wavelength convection in the Earth.