High‐temperature flow of rocks

A lot of activity has taken place in this area of tectonophysics during the last quadrennium, all of which has led to a much more fundamental understanding of the mechanical behavior and deformational processes of rocks undergoing flow in the crust and upper mantle. The most important advancements have come in the following areas: (1) direct observations of dislocation configurations and substructure in several important rock‐forming minerals deformed both experimentally and in natural environments, (2) determinations of preferred crystal orientations resulting from plastic deformation and from syntectonic and annealing recrystallization, (3) determinations of flow laws for several important types of aggregates undergoing steady state flow in laboratory experiments, and (4) detailed investigations of the internal structure of certain alpine‐type peridotites and of textures and deformational processes in peridotite xenoliths from the upper mantle. This information has provided the basis for preliminary interpretations of the creep state of the upper mantle as well as a better understanding of the origin of certain crustal structures.