212 NATIONAL OCEANOGRAPHIC PROGRAM LEGISLATION 



geophysics. The first step in determining environmental conditions is a thor- 

 ough mapping of the sea-bottom horizon. 



HYDBOGEAPHIO SURVEYS 



Maps of underwater areas are based on hydrographic surveys. Two types 

 of maps are required ; the bathymetric chart is composed of detailed delineations, 

 the contours, comparable to contoured maps of land areas ; the nautical chart 

 shows large numbers of soundings, a few contours, and considerable surface 

 detail needed for navigation. Although the nautical chart serves as a very 

 useful tool in scientific and commercial explorations, it is the bathymetric 

 chart frequently supplemented with original data, which provides the most 

 useful guide to engineering, mineral and fisheries resources, and the scientific 

 explorations of the Continental Shelf. It is the irregularities in the submarine 

 topography which control many elements in the sea environment. 



To be fully effective, the sounding data and data on the character of the 

 deep sea bottom need to be far more profuse and well-defined than is the re- 

 quirement for nautical charting. Yet, it is conceivable that in the immediate 

 future the marine navigator will accept and desire a fully contoured chart as 

 an improved aid in port-to-port navigation and in locating specific areas for 

 fishing and other activities referred to above and discussed below. 



GEOLOGICAIi OCEANOGEAPHY 



In conjunction with hydrographic surveys, the bottom needs to be systemati- 

 cally sampled in order to prepare a sediment-type chart as an overlay of the 

 bathymetric chart. This chart outlines the area and type of bottom — mud, silt, 

 sand, gravel, rock, etc., and includes information on sediment analyses. This 

 information is valuable for anchoring ships and floats containing instruments ; 

 for guidance in selecting sites for bottom installations of structures serving 

 as navigational aids, observation platforms, and drilling platforms, and for 

 monitoring instruments and defense hardware ; for guidance to the marine 

 biologist in commercial fisheries who relates sediment types to the abundance 

 of paucity of organisms which attract and support certain species of fif^h and 

 shellfish ; for guidance in locating mineral resources — the quartz sands of 

 certain sizes needed to replenish specific sands now nearly exhausted in certain 

 inland areas near the coast — the carbonate sands, heavy minerals, and the 

 environmental conditions which establish the present habitat of future petroleum 

 accumulation ; for determining the acoustical properties of the bottom in sonar 

 operations ; and for information of scientists in many fields, who are concerned 

 with attaining knowledge of the offshore sea bottom horizon. 



In conjunction with the bottom sampling of sediments there is a need to 

 determine systematically the distribution of sediments on the Continental Shelf 

 and the horizons of underlying rock by operation of a geological echo-profiler 

 which reveals the variations of thickness of unconsolidated sediments and the 

 areas of rock outcrop. These data provide the third dimension and are valuable 

 adjuncts in engineering and scientific considerations of the Continental Shelf 

 platform. 



GEOPHYSICAL DATA 



In order to obtain full use of the forces exerted by or modified by the mass of 

 continental rocks, it is necessary to determine the variations in mass and types 

 of rock by extending observations to the limit of the continental margins and into 

 the ocean basins. These observations include the use of gravity meters and mag- 

 netometers ; the geological echo-profiler, a seismic tool, also contributes to these 

 geophysical data. The resulting data are useful in oil and mineral explorations, 

 in satellite, missile, and inertial guidance systems, and in measurements of the 

 earth's geoid and the magnetic field. 



PHYSICAL AND CHEMICAL OCEANOGRAPHY 



Knowledge of the movement of water masses in the ocean — the tides, surface, 

 and internal currants — is important to surface and subsurface navigation, to 

 recovery of derelicts, to forecasting migrations of sea life, and to an understand- 

 ing of weather systems originating with the sea-atmosphere environment. This 



