In July 1972, the U.S. Office of Naval Research identified several areas that it interpreted as being of interest to the U.S. Navy. Four of these research areas were then selected for their special importance in understanding physical processes on the ocean floor. In some of these, a great wealth of data has accumulated over the past two or three decades, but controversy exists in the interpretation of the results. In others, new techniques have re- cently been devised that could lead to the collection and synthesis of new information. There was yet a third area in which little study had been...