The aim of this monograph is to provide mathematical bases and methods for analyzing geophysical problems for global geodynamic models of the Earth and planets. It presents computational methods, based on variational formulations of model problems used in all areas of geosciences. Tectonic plates, seismic waves propagation, geothermal and electromagnetic fields, global geodynamics, geomagnetic and gravity models are all addressed. Emphasis is placed on the variational approach to the problems studied, which involves numerical analysis, whilst preserving the physical nature of the problems. The book details numerous applications of geodynamic and plate tectonic models which relate to constructions such as nuclear power plants, high level radioactive waste repositories, deep mines and water dams, under critical conditions.