Neither plate tectonics nor Earth expansion theory is sufficient to provide a basis for understanding geoscience. Each theory is incomplete and possesses problematic elements, but both have served as stepping stones to a more fundamental and inclusive geoscience theory that I call Whole-Earth Decompression Dynamics (WEDD). WEDD begins with and is the consequence of our planet's early formation as a Jupiter-like gas giant and permits deduction of:(1) Earth's internal composition, structure, and highly-reduced oxidation state; (2) Core formation without whole-planet melting; (3) Powerful new internal energy sources - proto-planetary energy of compression and georeactor nuclear fission energy; (4) Georeactor geomagnetic field generation; (5) Mechanism for heat emplacement at the base of the crust resulting in the crustal geothermal gradient; (6) Decompression driven geodynamics that accounts for the myriad of observations attributed to plate tectonics without requiring physically-impossible mantle convection, and; (7) A mechanism for fold-mountain formation that does not necessarily require plate collision. The latter obviates the necessity to assume supercontinent cycles. Here, I review the principles of Whole-Earth Decompression Dynamics and describe a new underlying basis for geoscience and geology.