Horizontal Movements of the Earth's Crust

tangential movement of the earth’s crust, movements that occur in a direction parallel (tangential) to the earth’s surface. They are juxtaposed to vertical (radial) movements of the earth’s crust. Manifestations of the earth’s crust’s horizontal movement are the relative shifting of separate blocks of the earth’s crust along displacements, separations, and overthrusts, especially of the deep-seated type, as well as linear folding. Horizontal movements of the earth’s crust are primary or derivative from vertical uplifts and subsidences (for example, separations in the axial parts of uplifts, folding and overthrusts where sediments slide off uplifts). In the first case, in the opinion of a number of researchers, horizontal movements of the earth’s crust may be linked with the earth’s rotation on its axis and with the reshaping of the figure of the earth because of changes in the earth’s speed of rotation or because of convection currents in the earth’s mantle and the shifting of blocks of the lithosphere under the influence of these currents.

Contemporary horizontal movements of the earth’s crust are studied by means of repeated triangulations—primarily in Japan, the United States (California), and the USSR. Their speed is up to several centimeters a year; a similar rate is assumed for separations in the axial rifts of the midoceanic mountain ranges. Horizontal shifts along the earth’s surface during certain large-scale earthquakes have reached several meters, and in particular cases, more than 10 meters.