Effects of the relative lithosphere–asthenosphere motion on the global tectonic features

The relative eastward rotation of the asthenosphere with respect to the lithosphere is explained by the westward-directed offcenter rotation of the spinning Earth around the gravitational center of the Earth–Moon system (principle of hypocycloid gearing), and by the lateral viscosity variations at the base of the lithosphere. Independent geologic data favor a global westward drift of the lithosphere relative to the asthenosphere. Therefore, any attempt to investigate the mode of origin of the global tectonic features and the relationships among their tectonic components must consider this relative lithosphere–asthenosphere motion. As the angular velocity of the relative motion increases from the poles toward the equator, its effect on the global tectonic features also increases toward the equator. Consideration of the diverse effects of this relative lithosphere–asthenosphere motion on the west and east-facing subductions, on ternary plots, allows classification of east-facing island arcs into simple vs complex, and proximal vs distal.