Continental drift with deep cratonic roots

Abstract

The influence of the continental lithosphere and its root (or keel) on the continental drift of Earth is a key element in the history of plate tectonics. Previous geodynamic studies of mantle flow suggested that the cratonic root is moderately mechanically coupled with the underlying mantle, and stable continental drift on Earth's timescales occurs when the effective viscosity contrast between the continental lithosphere and the underlying mantle is approximately 10bsup3esup. Both geodynamics and seismological studies indicate that mechanically weak mobile belts (i.e., orogenic or suture zones) that surround cratons may play a role in the longevity of the cratonic lithosphere over geologically long timescales (i.e., over 1,000 million years) because they act as a buffer region against the high-viscosity cratons. Low-viscosity asthenosphere, characterized by slow seismic velocities, reduces the basal drag force acting on the cratonic root, which may also contribute to the longevity of the cratonic lithosphere. squfensp The role of the continental lithosphere and its root on the continental drift is reviewed from recent geodynamic and seismological studies. squfensp The cratonic root is moderately mechanically coupled with the underlying mantle and deformed by mantle flow over geological timescales. squfensp Orogenic belts or suture zones that surround cratons act as a buffer to protect cratons and are essential for their longevity. squfensp Low-viscosity asthenosphere may reduce the basal drag acting on the cratonic root and also contribute to its stability and longevity.