S2.15: The Role of Tectonics on the Emergence and Evolution of Volcanic Features
Volcanism is related to the plate tectonics geodynamic processes, usually occurring along divergent plate boundaries or within back-arc basins of converging boundaries above subduction zones. In most cases, the volcanic features appear within tectonic grabens, forming rift zones of the upper crust,both onshore and offshore. Thus, volcanoes may be aligned along tectonic trends,indicating the intermediate stress axis of the dominant extensional field along the rift zone. More rarely, strike-slip fault zones may also control volcanism, with more complex relationships between volcanic features and tectonic stress orientation. The evolution of the tectonic structures may control the evolution of the successive volcanic centres as well as their geometry. The opening and deepening of the rift zones in marine basins is accompanied by the appropriate growth of the volcanism and its volcanic relief, driving to the emergence of volcanic islands. The migration of the volcanic activity to another rift zone may follow the overall migration of the convergent boundary within a geological time-frame of several millions of years, depending on the rate of subduction and subsequent deformation in the back-arc area. The relation between tectonics and volcanism can be studied both in active volcanic areas as well as in older,eroded volcanic successions. The overall volcanic evolution can be studied against the tectono-sedimentary evolution of the hosting basin with comparison of slip rates of synsedimentary faulting and sedimentation rates throughout the basin’s evolution. In this session, worldwide examples of the above relations in active or ancient volcanic areas may be presented and discussed.