The discussion of the subject of the general morphometric series at a meeting of the geomorphological commission of the Moscow branch of the Geographical Society of the Academy of Sciences of the USSR and at the scientific conference of the Moscow Institute of Engineers for Geodesy, Aerial Photography, and Cartography (MIIGAiK) in the spring of 1960 resulted in a decision on the necessity for further studies of the patterns discovered. However, further work was very much hindered by the above-mentioned nonuniformity of the morphometric data available in the literature. We obtained comparatively uniform data only after publication of the "Neotectonic Map of the USSR" (Karta noveishei tektoniki SSSR) compiled by a large group of authors, with N.I. Nikolaev and S. S. Shul'ts as general editors (1959). In contrast to other specialized maps (geological, tectonic, etc.), this map reflects the dynamics of the Earth's crust; it clearly exhibits the tectonic structural forms which underwent subsidence or uplift over a relatively brief (geologically speaking) time period.
Notwithstanding the large inaccuracies in the map, due to the lack of knowledge of certain territories, excessive generalization of the structures, the crude scale of the sections scale, and other causes we succeeded in measuring 823 tectonic structural forms with sufficient accuracy for a first approximation. The preliminary data elicited from an analysis of this material will be presented below. The results of measurements performed on this map are listed in Tables 2 —6, and the reader can analyze the material presented by any available method.
It is seen from Table 2 that structures of certain orders dominate among those marked on the map. Structures of the smallest areas are about 10 km long and 5 km wide (28 structures).
Structures of the next order are about 30 km long and 10 km wide (143 structures). Then come structures 300 km long and 100 km wide (57 structures), followed by those having a length of 900 to 1300 km and a width of 100 to 300 km.
It may be assumed that the highest order is formed by tectonic structures over 1300 km long but relatively narrow (complex geosynclinal belts), and by structures whose width and length exceed 1000-1500 km (platforms); there exist only a few of these, and they were not included in our tables. Thus, the map marks structures corresponding to orders XI—XVI of the general morphometric series.
The tectonic structures form nodes, as it were, in which the structures are concentrated in considerable numbers and are extensively developed in the vertical direction (uplift or subsidence, see Tables 3-6). Structures
of intermediate dimensions are less widespread and are generally less developed vertically. In certain places the intermediate structures form secn-+dary "nodes", such as structures about 150 km long. At these nodes the morphometric indexes of the structures are multiples of the principal indexes in the morphometric series. A noteworthy feature is an abrupt increase in the number of structures wherever even a single one of their morphometric indexes (length or width) approaches 10, 30, 100, or 300 km.
The neotectonic map shows that the characteristic structures of platform regions possess plan shapes approaching circles and broad ellipses, while the characteristic structures of the geosynclinal belts are elongated, in the shape of ellipses and spindles, as has already been noted by several authors. These features of platforms and geosynclinal structures make it possible to differentiate corresponding "fields" in Figure 2, where the structures are grouped according to their width and length, i. e., regions which characterize the platforms and the geosynclinal structures.
In order to provide a vivid idea of the relative arrangement of structures characterized by different indexes, graphs were plotted in the simple ratios taken from the principal tables. These graphs clearly exhibit parts of curves corresponding to the most widespread structures (Figures 3 and 4).
An analysis of the vertical development of tectonic structures represented on the neotectonic map by the height of uplifts and depth of subsidences occurring over a comparatively brief geological time reveals a significant vertical underdevelopment of the positive structures compared with the height of uplifts of the same length and width according to the morphometric series (Table 1). This phenomenon can largely be explained by the vigorous denudation of the uplifts. Furthermore, the map features heights referring only to brief periods of geological time (Neogene and Quaternary), whereas the structures were undergoing uplifting over a considerably longer period of time. The uplifting of many structures had started earlier, in the Mesozoic and even in the Paleozoic.
The vertical development of the negative (subsiding) structures is fuller than that of the positive (uplifting) structures. This may be explained by their being preserved by sedimentary strata and possibly also by the additional load provided by the accumulating sediments.