ABSTRACT
Seeing is believing, or so they say. The geologist on land can readily believe the existence of the mountains, the rivers and their valleys and the strata exposed on fault scarps, and can set about explaining how they were formed and what forces of nature were at work. Marine geologists have no such advantage and have to create in their own minds, and by means of maps and photographs, the scenery of the ocean floor before they can get to work. They have to devise means to measure the ocean depths, to interpolate and correlate these into charts that even now are of very variable quality, and to lower cameras and sampling equipment on long wires to obtain more detailed data. And yet marine geologists have led the revolution of the past forty years in the understanding of global geology through the concepts of plate tectonics. The shape of the ocean floor has played a significant role in initiating this revolution.
