On The Dynamics of Convergent Plate Boundaries and Stress in the Lithosphere

Abstract

The evolution of active continental margins and island arcs is closely related to the process of subduction of (predominantly) oceanic lithosphere. In this paper we deal with some aspects of the dynamics of the subduction process. Understanding the dynamics is taken to be a prerequisite for improving our insight into the relation between upper mantle processes and structures or processes near the surface. A major force associated with the subduction of oceanic lithosphere is the slab pull resulting from the density contrast between the cold and dense descending slab and the surrounding warmer mantle. This force is generally assumed to be compensated by resistive forces acting on the slab. Here we emphasize that such a compensation may be valid for a plate's convergent boundary as a whole but certainly not always locally for each segment of the trench system. Transmission of stress from the subducted slab towards the attached lithospheric plate at the surface is possible, and taking this into account provides insight into the relation between upper mantle processes and tectonic processes near the surface (e.g. accretion of sediments at trenches, and uplift, subsidence and tilting of continental margins).