MODERN CONTINENTS

On an Expansion Tectonic Earth, prior to 250 million years ago, the ancient supercontinents existed as a complete continental crustal shell encompassing the entire Earth with no intervening oceans. This supercontinental phase lasted for some 3,750 million years and ceased with the breakup of Pangaea during the late-Permian. During these ancient times formation of the supercontinents simply involved a progressive, evolutionary crustal process during a prolonged period of crustal stretching and changes to both Earth surface area and surface curvature through time.

The outlines and configurations of the supercontinents were controlled and dictated by changes to the ancient sea-levels and coastal shorelines.

The modern continents have only existed in their current form since breakup of the ancient Pangaea supercontinental crust first started some 250 million years ago.

The modern continents simply represent the fragmented remains of the ancient Pangaea supercontinental crustal shell.

This fragmentation and breakup occurred because the ability of the ancient supercontinental crusts to continue to stretch during on-going increases in Earth surface area was finally exceeded during late-Permian times. Once crustal stretching was exceeded the supercontinental crust then ruptured, broke apart and fragmented to form the modern continents and opened to form the intervening modern oceans.

Many of the modern continents now have a nucleus of most ancient crusts which are surrounded in turn by younger sedimentary basins or orogenic rocks. These orogenic rocks generally comprise older sediments that have been heated and folded. This global network of ancient sedimentary basins and orogenic rocks is analogous to the modern oceans whereby the network of crustal weakness contained within these basins represents the precursor to the modern mid-ocean-ridge spreading zones. Once rupture and separation of the supercontinents began, part of these fragmented sedimentary basins then remained attached to one continent and other parts remained attached to adjoining continents.

When describing the development and subsequent history of the modern continents, geographical orientations relative to the ancient equator will be given in lower case, for example, the long axis of Australia was orientated north-south throughout the Precambrian and Palaeozoic times—as distinct from its current east-west orientation. In contrast, current geographical descriptors and names of continents relative to the present-day equator will be given in upper case, for example North America.