Part 1 - Introduction

It was the observation of the uplifted but almost totally undisturbed alluvial sedimentary beds the top of the Bolivian Andes that caused the author to consider the forces needed to lift the western edge of the South American continent from approx. 3Km below sea level to approx. 6Km above sea level.

A study of the published literature on tectonic movements 9,42 et al of the major continental plates away from Pangea in the Permian era to their present day positions clearly demonstrate that the movements have been continuously sustained albeit in different directions. At present these movements have been mainly attributed to the ‘ridge push’ and the ‘slab pull’ forces proposed by Hess18 that are created by heated convection currents within the earth’s mantle. The same study has also shown that the unbalanced centrifugal or inertial forces have not been considered and even positively discounted 34 as a mechanism for tectonic movements.     

However the author on looking at these plate movements from a mechanical point of view, finds it difficult to understand how this sustained and presently continuing uni-directional movement of the massive continental masses in their different directions can be adequately explained by the ‘slab-pull’ system in what must obviously be a continuously changing omni-directional convection current flow pattern.

Fig. 1. Simplified diagram showing the precession of the equinoxes which are often referred to as the Milankovitch Cycles

Fig. 1. Simplified diagram showing the precession of the equinoxes which are often referred to as the Milankovitch Cycles

The unidirectional movements both east and west of the various plates away from the predominately central or ‘fixed’ African plate, together with the complex circulatory current system led the author to consider the possibility that the prime source of the tectonic activity could well be function of unbalanced centripetal forces that are generated by an unbalanced rotating body.

This view was reinforced by the consideration of the periodic precession of the equinoxes (Fig.1). The periodic precession of the geometric axis, or true North of the Earth with respect to the North Star and the change in the orbital motion around the Sun 28, displays a very similar characteristic to the mechanical behaviour of a rotating shaft with an unbalanced load 2,24. These periodic precessions are often referred to as the Milankovitch cycles. The nature of the precession motions suggests that consideration be given to the possibility that the unbalance may well be due to the mass of the heavy core of the Earth not being totally symmetrical about the major axis of rotation

Recent publications by Sager & Koppers 37 describe the movement of the Earth's spin-axis from as far back as the late Cretaceous. The movement of the Earth's spin-axis referred to by the authors as an 'apparent polar wander path' (APWP), is of the order of 3-10 0 my-1. Sager & Koppers 37as well as Kearney and Vine21 (quoting the work of Courtillot and Besse6 ) suggest that this phenomenon might be the result of changes in the Earth's principal axis of inertia caused by the redistribution of the mass in the mantle.

However from a purely mechanical point of view, this phenomenon may also be attributed to the movement of the centre of mass of the core relative to the principal axis of rotation. This scenario is likely, as recent work by Waller & Home 43 has shown that the core rotates faster than the mantle and crust.

This paper will attempt to demonstrate that (1) the forces needed to sustain tectonic movement are generated as a result of centre of mass not being coincident with major axis of rotation of the earth and (2) 'sea floor spreading', the 'destruction of crustal mass at sub-duction zones', as well as orogenic activity are a consequence of the unbalanced centrifugal forces acting on the Earth's crust.

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