A new model of the Earth’s isostasy. The shape of our planet (geoid) can be quite closely approximated by the figure of equilibrium of a rotating liquid of the same mass (spheroid) enclosed in separate shells. The spheroid or theoretical geoid is characterized by a small compression value, s = 1/298.25, depending on the angular velocity of rotation and the law of mass distribution inside the Earth [4]. At one time, when the shape of ourplanet was studied by geophysical methods, a theory of isostasy appeared. In that theory the equilibrium state of the Earth was replaced with that of its crust (and later on, lithosphere). It conformed to that epoch’s standard of knowledge about the Earth’s structure and agreed with the objectives of use of the concept. From our present-day knowledge about the Earth’s structure, the above substitution cannot be regarded as reasonable. To solve geotectonic problems, we had to introduce a new model for the equilibrium state of the Earth as a whole which we named as geoisostasy. Its most detailed description can be found in earlier published works [6,10]. Its main points may be reduced to the.following. Geoisostasy should correspond to the Earth’s state it would have if its substance within each shell became liquid without mixing. In such case, our planet could be characterized as a set of certain-level surfaces being a system of spheroids with ever-decreasing compression coefficients formed by the entire Earth’s masses including its hydrosphere and atmosphere. Practically, the spheroid closest to geoid is the most significant.......