Four Phases of Geographical Development

Research outlined in this website has shown that continental and seafloor geographical development on an Expansion Tectonic Earth is an evolving process which is intimately related to changing Earth radius, surface area, and surface curvature. Four primary phases have been recognised and this process is graphically summarised below in relation to changing Earth radius over time.

These four overlapping phases of continental and seafloor geographical development include:

Phase 1:

An Archaean to mid-Proterozoic—times older than 1,600 million years ago—phase of minimal increase in Earth radius.
The increase in surface area during this phase was readily absorbed during the first beginnings of continental crustal stretching and was marked by early sedimentary basin development and intrusion of granite and volcanic rocks. Deposition of sediments eroded from the exposed lands was confined to a global network of continental sedimentary basins which coincided with relatively shallow continental seas. Subtle jostling of each of the ancient plates during changes in surface curvature was first initiated during this phase, in particular within the established network of sedimentary basins, giving rise to long linear zones of crustal weakness. Because of the prolonged period of time involved in this phase, the continental crust had a subdued featureless topography for much of the time and continental seas were relatively shallow. Single to multi-celled organisms first became established and evolved during this phase.

Phase 2:

A mid-Proterozoic to Carboniferous—from 1,600 to 360 million years ago—phase of steady to rapidly increasing Earth surface area, crustal stretching, and changing surface curvature. The increasing surface area during this time continued to be absorbed within the continental crusts as on-going crustal stretching, accompanied by magmatic and volcanic intrusions. Crustal stretching was again confined mainly within the coincident network of crustal weakness, sedimentary basins, and shallow seas. Over time, the network of sedimentary basins and seas continued to increase their surface areas throughout the early- to mid-Palaeozoic Era— 560 to 360 million years ago—as crustal stretching also increased. Movement of the various crustal plates during adjustments to changing surface curvature resulted in multiple and often reoccurring phases of crustal jostling and tectonic activity, followed by renewed basin extension as stretching continued. The topography contrast between the low-lying sedimentary basins and exposed continents gradually increased during this phase, in particular during periods of crustal interaction and early mountain building. Hard shell and invertebrate life forms and fishes were well established during this phase.

Phase 3:

A Carboniferous through to late-Permian— 360 to 250 million years ago—transitional phase, where continental crustal stretching was exceeded and stretching changed to crustal rupture, rifting, and initiation of continental break-up and opening of the modern oceans. Continental seas commenced draining and deposition of sediments then progressively shifted away from the established continental sedimentary basins into newly opening marine basins. Evidence for this early marine basin phase is now preserved seawards of the continental shelf margins and as remnant ocean plateaux within many of the modern oceans, such as the Lord Howe Rise in the Tasman Sea. During this phase reptiles, dinosaurs, and mammals evolved and dominated the lands.

Phase 4:

A post-Permian— 250 million years ago to the present-day—phase of relatively rapid increase in Earth surface area and rapid opening of the modern oceans. etc. Here, crustal stretching predominantly occurred within the modern oceans along well-defined mid-ocean-ridge spreading zones. During this phase, the increase in surface area and volcanic activity within the mid-ocean-ridge zones gradually exceeded the input of sediments from the continents. By the early-Jurassic Period the seafloor volcanic rocks were then exposed and preserved as seafloor crust. All seafloor crusts formed since then have remained preserved within each of the oceans. Two sub-phases are also recognised during this time, with each phase corresponding to the distribution of Mesozoic and Cenozoic seafloor crusts. During this phase 4 a number of extinction events were also prominent where dinosaurs, for instance, became extinct and were superseded by the mammals.