Subduction zones: Their diversity, mechanism and human impacts

Subduction is not only the counterpart process to seafloor spreading in the plate tectonic regime, but is also the major driving mechanism of plate motions. Various features characteristic to subduction zones are reviewed from a geotectonic viewpoint, and their impacts on human soeciety are considered. The features of subduction zones are difficult to explain by a single model. The importance of recognizing the existence of two basic and contrasted modes in subduction, controlled by the strength of coupling between subducting and overriding plates, is demonstrated. The two modes are High Stress Chilean-type subduction and Low Stress Mariana-type subduction. Collision and accretion of buoyant features on seafloor, an inevitable consequence of subduction, is important in the evolution of continents.