Geodynamics / Геодинамика

The plate tectonic model provides a framework for understanding many geodynamic processes. Earthquakes, volcanism, and mountain building are examples. The plate velocities, 10– 100 mm yr−1, imply a fluid-like behavior of the solid Earth. Hot mantle rock can flow (behave as a fluid) on geological time scales due to solid-state creep and thermal convection. The hot mantle rock is cooled by heat loss to the Earth’s surface resulting in a cold thermal “boundary layer.” This boundary layer is rigid and is referred to as the lithosphere. The surface lithosphere is broken into a series of plates that are in relative motion with respect to each other. This motion results in “plate tectonics.”Plates are created at mid-ocean ridges, where hot mantle rock ascends. Partial melting in the ascending rock produces the magmas that form the basaltic ocean crust. The surface plates reenter the mantle at ocean trenches (subduction). The cold rock in the plate (lithosphere) is denser than the adjacent hot mantle rock. This results in a downward gravitational body force that drives the motion of the surface plate. Complex volcanic processes at subduction zones generate the continental crust. This crust is thick and light and does not participate in the platetectonic cycle. Thus the continental crust is about a factor of 10 older, on average, than the oceanic crust (1 Gyr versus 100 Myr). <...>