| Abstract: | The modern geodynamic model known as ‘New Global Tectonics’ or ‘Plate Tectonics’, elaborated in the past twenty years, is the synthetic result of the great post-war advances achieved in marine geophysical methods, deep-sea drilling technology, worldwide monitoring of earthquakes and paleomagnetics. It represents a ‘mobilistic’ view of the earth based on continental drift and sea-floor spreading (as outward manifestation) and convection currents in the mantle (as interior driving motor). The predictions of this model appear to correspond fairly well with observations about the kinematic evolution of the lithosphere during its younger (or Phanerozoic) phase. Extrapolations to Precambrian times run into conflict, however, with our knowledge of the earlier global evolution and some major revisions of the model appear to be imperative, especially in the field of geochemistry.In comparison, the model of the ‘undation theory’, conceived since 1931, has grown into a synthesis between the (sometimes extreme) mobilistic and fixistic positions. Its driving force is supposed to be primarily provided by the liberation of free energy in the earth's core and its stepwise rise to the surface in an irreversibly outward transport. This general form of energy flow occurs through rheological and geochemical processes, which lead to accumulation of potential energy and its release expressed primarily by vertical deformations of the surface — called ‘undations’ —, of various dimensions.By means of the prognosis—diagnosis method of scientific verification, this view has been repeatedly checked in test-cases of global tectonics.A notable item of this paper is the checking of both models by a comparison of global tectonic features and the major anomalies of the earth's gravity field (as ascertained from the deviations observed in the orbits of man-made satellites).A plausible rheological interpretation of these geoidal anomalies through their correlation with the major tectonic features of the earth can be produced by the undation model, whereas (so far) the model of the new global tectonics has remained silent on this allimportant geodynamic issue. |
