Global tectonic maps

Abstract

The original kinematic plate tectonic model proposed that the outer shell (lithosphere) of the Earth is divided into a small number of nearly rigid plates that slide over the weak asthenosphere. The plates are the surface thermal boundary layer of upper-mantle or global-scale mantle convection, and the descending slabs are the primary active components of the convective system. The plate boundaries are generally narrow and are characterized by earthquakes and volcanoes. The plates, however, are not really rigid or undeformable, and the plate boundaries need not be localized (Dewey and Bird, 1970; Gordon, 2000; Anderson, 2001, 2002; Steinberger et al., 2004). Not only is the plate-slab system the main driver of plate tectonics and mantle convection, but much of the energy dissipation may be in this part of the system as well, rather than in mantle viscosity (Conrad and Hager, 2001). Plates may be held together by lateral compression-or absence of extension-rather than by strength or rigidity; rocks are strong in compression but have little resistance to extension.