During the tectonic cycle, new, but recycled crust is created at "divergent boundaries" and old crust is driven into the asthenosphere by "subduction.
A tectonic cycle is the procedure by which the Earth's outside crust restores itself. Structural plates are continually falling or ascending from the hot magma underneath the covering. As these plates slide into the magma, they warm up and soften the stone; as they ascend from the magma, they cool to frame strong shake. The structural cycle results in seismic tremors and volcanoes as the colossal powers of the Earth push sufficient against shake plates to cause gigantic changes.