The degrees of flattening of the lithosphere, hydrosphere, and atmos phere corresponding to their new rotational regimes will not be the same. The oblatenesses of all three geospheres would be identical only if the rotational velocity of the Earth remained constant for a quite long period. With respect to the dynamics of the Earth, this means that any fluctuation in the diurnal velocity gives rise to a corresponding "triple pulsation" in the shape of the planet along its rotation axis. The theoretical considera tions presented above, and also observational data, indicate that the length of the day varies. Consequently, there is no reason to doubt the existence of out-of-phase pulsations of the geospheres along the axis of diurnal rotation. Obviously, these pulsations are effected as a result of the arrival at the Earth of solar thermal energy.
Let us denote this out-of-phase pulsation of the geospheres (lithosphere, hydrosphere, and atmosphere) along their diurnal-rotation axis as t he second-order regularity in the evolution of the Earth.
"...the water of the Earth constitutes a single entity, all parts of which are inseparable from one another in nature, because of the close relation between them... It is just because water possesses such special properties (unusual mobility, enormous molecular and gravitational forces) that it may be thought of as a single entity. This characteristic has determined the exceptional role of water in the history of our planet and also determines its role at present, a role which is (and was in the past) a very active one" (Lichkov, 1959, pp. 107- 108).
In accordance with this, the hydrosphere may be assumed to react to variations in the rotational regime of the Earth as a single entity. Fluctuations in the length of the day cause the hydrosphere to shift relative to the lithosphere, sometimes equatorward and sometimes poleward, and the coastline will everywhere be changed correspondingly.
Let us imagine that the rectilinear coast of a continent lies exactly parallel to one of the meridians, from the equator to the pole, and that tide gauges are placed uniformly along the entire coast. Let us also assume that the degree of flattening of the lithosphere remains constant even though there is a change in the length of the day. Then, if the angular velocity of the Earth increases, the tide gauges will show, beginning at some specific latitude, a regular lowering of sea level toward the pole and a corresponding elevation of sea level in the direction of the equator. If
the diurnal rotation of the Earth slows down, on the other hand, the tide gauge readings will be just the opposite, so that any variations in the rotational regime of the planet will be clearly indicated. Next let us assume that the land extends in a rather narrow, long strip along one of the parallels in the middle latitudes. In this case, an increase in the rotational velocity of the Earth will bring about an ingression of the sea along the north coast, since a water "overflow" will occur as a result of the increased centrifugal forces (for example, along the north coast of the Soviet Union, along the Mediterranean coast of Africa, etc.). For a slowing down of the diurnal rotation, on the other hand, this effect will be observed at the south coast, due to the decrease in the centrifugal forces (for example, along the coast of the Gulf of Mexico, along the north coast of the Mediterranean, etc.). The sea-level variations occasioned by the "overflow" of the water will be a minimum (zero) at the pole and the equator and a maximum in the middle latitudes.
Existing hypotheses give different explanations for the fluctuations in the levels of the oceans and seas (that is, for the changes in the mutual positions of the land and the water areas), but they do not offer any definitive answer to this complex question. In oceanography the observation system is set up in such a way that the instruments are based on immobile seg ments of the Earth's crust, and the level of the sea is taken as the moving object. In geology, on the other hand, sea level is taken as the constant element, and displacements of the Earth's crust are observed relative to it by means of a system of depth gauges. Since neither of these two observation systems is actually at rest, a solution can be found only by means of combined methods. To do this, in addition to the factors which are known to influence the sea level (such as tectonic phenomena, tides, winds, atmospheric pressure, temperature, precipitation, erosion, river runoff, etc.), certain other no less significant factors must be taken into account (for instance, the shifting of the hydrosphere relative to the lithosphere and the "overflow" of water as a result of changes in the magnitude of the Earth's centrifugal forces). All these factors can operate in different directions, and we are only able to observe their resultant effect.