for efficient management of the marine environment and its 

 resources, and, in particular, for management of the heavily used 

 sector of the sea floor on the continental shelf. Here use of the sea 

 floor for food resources (finfish and shellfish) and for recreational 

 purposes (bathing, boating, and sports fishing) conflicts with all 

 other uses (dumping of sewage sludge, dredge spoil, industrial 

 wastes; dredging of channels and for aggregate; and the construction 

 of deepwater terminals, oil rigs, and offshore powerplants). 

 Environmental engineers and decisionmakers must have quan- 

 titative information on the pattern of sediment transport on the 

 continental margin if they are going to optimize these conflicting 

 uses. They must know whether the surfaces on which they are 

 dumping and building are eroding or aggrading; and they must trace 

 the natural sediment pathways that pollutants follow. 



This chapter will describe seven major categories of federally 

 supported programs in marine geology and geophysics. The first 

 three sections are those that examine the properties, structure, and 

 history of the oceanic crust and upper mantle from its generation at 

 sea-floor spreading centers to its ultimate destruction in ocean 

 trenches. The fourth section describes programs examining the 

 relatively passive continental margins such as those that surround 

 the Atlantic Ocean. Studies of the sediment record of paleo- 

 oceanography and paleoclimatology are discussed in the fifth. The 

 sixth section reviews federally supported research on mineral 

 resources of which manganese nodules on the deep-sea floor are 

 perhaps the most potentially important. The last section discusses 

 the sediments themselves, including sedimentation processes and 

 properties. 



The Generation of the Sea Floor and Processes Operating at Ridge 

 Crests 



Midocean ridges are the most extensive morphologic features on 

 the earth's surface, and within the framework of plate tectonics, they 

 represent the divergent or accreting margins of the plates. Studies of 

 the worldwide distribution of earthquakes, presently being con- 

 ducted by the USGS, and of the distribution of magnetic anomalies 

 in the ocean basins, have allowed an accurate mapping of these 

 accretion zones and, to a first approximation, an analysis of the rate 

 of sea-floor generation along most of the ridge systems. Current 

 studies seek to understand the tectonics, petrology, and 

 geochemistry of the accretion processes occurring along these 

 ridges. 



The most intensive examination of a ridge crust ever undertaken is 

 project FAMOUS (French-American Mid-Ocean Undersea Study). 



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