The past decade has seen remarkable advances in ideas about the earth and the origin of its surface features. Among the most significant results of efforts during this decade is the realization that the tectonically active belts may be considered as the edges of large lithospheric plates moving relative to each other. In addition, there is evidence of lateral inhomogeneities in the mantle which may be related to the driving mechanism for these motions. It is difficult to overstate the importance of these ideas in drawing together the different disciplines which make up the earth sciences.

It is time for a second look at these ideas. The short-term movements in the seismically active belts appear to be related to the long-term movements preserved in the geologic record, hence, it is possible to study process as well as result. It also is apparent that there have been major movements, primarily vertical, within the lithospheric plates that are apparently unrelated to the relative horizontal movements of the plates.

The International Council of Scientific Unions has established a new Commission, the Inter-Union Commission on Geodynamics, to encourage research in these areas and to provide international coordination of efforts.