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Structural Geology Symmetry Features of the Earth Associated with the Gravitational Field

parallels, 62nd, spreading, equator and figure

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SYMMETRY FEATURES OF THE EARTH ASSOCIATED WITH THE GRAVITATIONAL FIELD, STRUCTURAL GEOLOGY, AND HYDROGEOLOGY In my recent book entitled "The Natural Water of the Earth and the Lithosphere" (1960), I formulated a new theory of orogenesis. According to this theory, orogenesis is part of a process of re-formation of the planetary figure of the Earth related to variations in the velocity of terres trial rotation, which cause an increase or a decrease in the planetary or polar flattening of our planet. I called this re-formation of the Earth's figure spreading of the Earth.

According to Shmidt's theory, spreading first took place during the period in which the spheroidal body of the Earth formed from an angular asteroid. The spreading which occurred at this time, during the increase in the dimensions of the asteroid and as a result of this increase, was the biggest spreading in the history of the planet. It may be assumed to have taken place when the Earth changed from a region of cohesive forces into a region of attractive (gravitational) forces. Spreadings recurred during each new orogenetic process.

Such orogenesis, then, is the part of the re-formation of the figure of the planet which occurred in the solid envelopes of the Earth, and which manifested itself most distinctly in the lithosphere. It is this part of the re-formation of the figure which we have called the spreading of the solid body of the Earth. The spreading takes the form of large-scale subcrustal tangential displacements of mass at the poles, at the 62nd parallels, and at the equator. Such displacements do not take place at the 35th parallels.

As a consequence of the tangential mass displacements over large distances, upheavals and subsidences of the topography take place at the 35th and 62nd parallels, that is, at the two definite boundaries of the zones, and also at four definite antipodal meridians located 90° from one another. This situation may be assumed to result from the existence of critical parallels and critical meridians which develop during rotation of the planet and which determine the structure of the Earth. The shape of the Earth,

therefore, is not something which was handed down to it from a previous liquid phase (as was assumed, for instance, by Clairaut). Rather, it is an acquired characteristic which can be attributed to the loss by the planet of the angular form possessed by the asteroid.

The empirically observable distribution of mountain chains over the terrestrial ellipsoid can be substantiated mathematically. Stress-discharge zones must have appeared in the crustal layer, which also explains the existing distribution of mountain ridges. The most deformed zones should be: the equator, the critical parallels at t35° and ±62°, and the poles, as the studies of Stovas over the last ten years have demonstrated. The maximum stress and maximum shifting of areas is at the 62nd parallel and at the equator, and minimum shifting takes place at the poles and at the 35th parallels.

The equator and the 62nd parallel are conjugate parallels. By this we mean that an increase in the length of one of these results in a decrease in the length of the other. The length of the 35th parallel, however, remains constant for a change in the degree of flattening. The conjugate variation of the length of arc of the equator and the 62nd parallels should cause deformations (tangential latitudinal stresses) there. These stresses are a maximum at the equator and they decrease with the approach to the 35th parallel, where they drop to zero. Further on, according to Stovas, the sign of the stress is reversed. It continues to increase toward the high latitudes, reaches a maximum at the 62nd parallel, and then decreases toward the pole, where it is once again zero. In general, as Stovas points out, a meridional warping of the surface of the Earth's figure should be produced. The meridional tangential stresses cause latitudinal deformations.

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