The problem of scale changes in geology and geophysics is discussed as they affect the methods, concepts, and axioms of structural studies on a megametric scale. This is necessary for the construction of megametric and geonomic tectonic maps and in defining the basis of paleophysics. Geodynamics can be applied to the large scale problems of chronologic correlation. The classification and megadynamics of crust and mantle are discussed in terms of data and methods, megametric and geodynamic mechanics, submarine morphology, and marginal zones. Recent deformation of the internal and peripacific regions is described. Bimarginal structures of the Caribbean and Mediterranean types are considered. Structures existing on a megametric scale and the phenomena linked to them represent the transition between the kilometric scale of geology and the geonomic and astronomic scale of geophysics.