Plate tectonic theory insists that the radius, and hence mass of the Earth remains constant over time. This insistence was formulated well before the advent of modern space-based observations about the Earth which now suggests otherwise. It is emphasised that plate tectonic theory relies solely on the untested premise that the radius of the Earth has remained constant since formation. If this premise is wrong then plate tectonics must also be wrong, regardless of the vast amount of research effort and monies already spent, or perceived evidence in support of the theory.

In plate tectonic theory, as each of the modern oceans open, new volcanic lava extrudes along mid-ocean-ridge spreading centres allowing new seafloor crust to solidify and form. To maintain a constant radius Earth, it is postulated that an equal amount of pre-existing crust must be disposed of elsewhere and returned to the mantle by a theorized process called subduction. This subduction process forms the primary basis of plate tectonic theory and, as a consequence, is essential in maintaining a static radius Earth premise.

Alternatively, for an Expansion Tectonic Earth the radius and mass are not constant over time in accordance with modern space-based observations. The very same volcanic lava extruded along the mid-ocean-ridge spreading centres again widens the oceans and increases the surface area of seafloor crust. Similarly, fluids and gases originating from within the crystal lattices of the volcanic lava are expelled during eruption adding new water and gases to the oceans and atmosphere over time.

For an Expansion Tectonic Earth this increase in surface area of all the oceans occurs as a direct result of an increase in Earth radius. Surface area of each ocean is then shown to be cumulative with time. Because of the increase in Earth radius and surface area there is no requirement for any net disposal of excess crust by subduction processes, nor is there a need to consider the existence of pre-existing crusts in order to maintain a constant surface area and Earth radius premise.

On an Expansion Tectonic Earth it is the mechanisms governing change in surface curvature during increase in radius that gives rise to all geological phenomena observed on Earth today. These phenomena include commonly observed features, ranging from formation of simple joints and folding in rocks, through to more complex tectonism seen in mountain formation. All observed geological phenomena, in turn, are also linked to evolving changes in sea levels and coastal outlines, through to erosion of the landscapes and the evolution and demise of species.

Plate tectonics fits scientific data about the Earth to plate theory, whereas Expansion Tectonics allows the data to define and quantify its own theory.