Geography Observations

It is important to appreciate that the distribution of ancient seas and modern oceans on these geographical small Earth models is based on published coastal outlines. These coastal outlines were draped over each geological model in turn and shaded blue to emphasise their distributions. Each small Earth model simply represents a snapshot in time and, in reality, there was a continuous spectrum of change between each model.

This distribution of ancient seas and modern oceans also defines the distribution and assemblage of the ancient supercontinents. On an Expansion Tectonic Earth it is the configuration and distribution of the ancient continental seas that defines the ancient supercontinents, and the progressive change in coastal outlines defines the evolutionary change from one supercontinent to the next. The named ancient supercontinents and seas can be seen at

The significance of the style and distribution of sedimentary basins and seas on each of the pre-Permian small Earth models can only be fully appreciated by considering this in relation to the "Four Phases of Geographical Development", as noted separately above. Change in Earth radius during the entire Archaean to Mid Proterozoic Phase 1 amounted to less than the thickness of a human hair per year extending over 1,600 million years. During that time erosion of the elevated land surface was able to keep pace with changing surface curvature. The land surface would have been low and subdued, and the sedimentary basins were relatively shallow and extensive.

Throughout Phase 2 changes in Earth radius steadily increased from microns to millimetres per year. This is reflected in the geographical models by the changing configuration and outlines of the various continental seas. Relative elevation of the land surface also increased and a modern erosional and drainage cycle was initiated. These geographical changes, in turn, drove evolution of the species and initiated a number of prominent extinction events.

The Carboniferous to Late Permian Phase 3 was a time of unprecedented change to the ancient Pangaean Earth. During this relatively short time the ability for the continental crust to stretch and extend was exceeded which resulted in crustal rupture and breakup to form the modern continents. Breakup then initiated formation of the modern oceans resulting in draining of the ancient seas from the lands into the emerging marine basins. This phase coincided with the major end-Permian extinction event. ,

The final Phase 4 is marked by opening of the modern oceans and was accompanied by extrusion of basaltic lava along the mid-ocean-rift zones and expulsion of new water and atmospheric gases. This phase is faithfully preserved within the seafloor crusts and forms the basis for small Earth modelling on an Expansion Tectonic Earth.