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The microtopography of the continental shelf in five areas between Nova Scotia and New York was investigated with side-scanning sonar. The results were checked against those previously obtained by conventional methods in all areas and against later visual observations of the bottom from a research submersible vessel in two areas. Side-scanning sonar proved to be an ideal device for learning the distribution and relationships of rock, boulder, and sand bottoms and for measuring the patterns and trends of several sizes of sand waves and of large ripple marks.

Large-scale recovery from beaches and piers began only about 40 years ago, and soon afterward new exploration methods revealed the presence of economic concentrations of oil and gas, sand and gravel, and some heavy minerals beyond the beach. These materials are in relatively shallow waters of the continental shelf and now are known well enough to be considered reserve ores. Rapid success for them led to immediate expectation of marine mining of many other minerals that have higher value per unit weight, but they occur in deeper waters beyond the shelf where conditions are more difficult and costs are higher. They include phosphorite, ferromanganese nodules and crusts, and polymetallic sulphides. All are still potential resources that cannot yet be considered reserve ores., Large-scale recovery from beaches and piers began only about 40 years ago, and soon afterward new exploration methods revealed the presence of economic concentrations of oil and gas, sand and gravel, and some heavy minerals beyond the beach. These materials are in relatively shallow waters of the continental shelf and now are known well enough to be considered reserve ores. Rapid success for them led to immediate expectation of marine mining of many other minerals that have higher value per unit weight, but they occur in deeper waters beyond the shelf where conditions are more difficult and costs are higher. They include phosphorite, ferromanganese nodules and crusts, and polymetallic sulphides. All are still potential resources that cannot yet be considered reserve ores.