©A.D. MACKAY        




I posit the ‘clam-shell expansion’ model which describes the evolution of the Earth’s crust since Pangaean Earth times. This was a lop-sided development wherein the Pacific Ocean bed of new crust was built between two large landmasses, Laurasia and Gondwana as they progressively separated from one another. These two super-continents define the two components of the ‘clam-shell’ and they were ‘hinged’ together in what is now the Mediterranean region.





















In this role as a hinge, the Mediterranean’s original configuration has been determined. A strike/slip relationship between the African and Euro-asian plates has been confirmed as an anti-clockwise rotation of northern Africa and a resultant thinning of the crust in what is now Libya, Egypt and the eastern Mediterranean.











Other aspects of the evolution of the Earth’s crust have come to light in this work. Some regions of the crust have been successively strained to much thinner profiles (Mohos) while others have even been strained to failure point. Contour maps, with information derived from various sources, define the Moho depths for each continent. These successive stages of crustal thinning are consistent with an Earth gradually increasing its diameter by the addition of mass from below the crust.









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