The many surface expressions of mantle dynamics

Abstract

Plate tectonic theory suggests that present-day topography can be explained by the repeated interactions between the tectonic plates moving along Earth's surface. However, mounting evidence indicates that a significant proportion of Earth's topography results from the viscous stresses created by flow within the underlying mantle, rather than by the moving plates. This dynamic topography is transient, varying as mantle flow changes, and is characterized by small amplitudes and long wavelengths. It is therefore often hidden by or confused with the more obvious topographic anomalies resulting from horizontal tectonic movements. However, dynamic topography can influence surface processes and thus enter the geological record; it has, for example, played a role in the establishment of Amazon drainage patterns. In turn, surface processes such as the erosion of topographical anomalies could affect mantle flow. This emerging view of dynamic topography suggests that the concept of plate tectonics as the driver of surface deformation needs to be extended to include the vertical coupling between the mantle and the surface. Unravelling this coupling back in time with the help of models and the geological record can potentially provide unprecedented insights into past mantle dynamics. © 2010 Macmillan Publishers Limited. All rights reserved.