ACTIVE DEFORMATION OF THE CONTINENTS

Whereas relatively narrow bands of deformation define oceanic plate boundaries, in continental situations deformation is shown to be distributed over much broader zones. The complex and heterogeneous nature of boundary regions between major plates is outlined with reference to the Mediterranean and the Himalayas. Relatively aseismic regions have traditionally been defined as microplates but although they are presently acting as rigid blocks undergoing slow deformation, it is argued that this need not always have been the case, and that deformation may simply have moved elsewhere. Broad zones of deformation surrounding rigid blocks are highlighted as fundamental to the analysis and interpretation of continental tectonics. Detailed theoretical consideration is given to the kinematics of distributed formation and the dynamics of continental deformation. -A.J.Barker