Another aspect involves chemical fluxes at the seafloor boundary. Understanding of 

 seawater-crustal interactions has been greatly enchanced by the recent study of fluids issuing 

 from hydrothermal vents in midocean ridge areas. Analyses of these fluids provide important 

 information on the chemical compositions of exchanges between the fluid oceans and the solid 

 earth underlying them. 



These studies require various experimental and sampling strategies, including in situ pumping 

 and filtering, sediment trap deployment, in situ experiments on the ocean floor, and time-series 

 sampling systems. 



fi/larine chemists in the 1990's will need to perform chemical measurements and sampling with 

 greater resolution in space and time than is now possible. They will give more attention to 

 short-lived, unstable, chemical species responsible for chemical dynamics in the ocean. They 

 must be able to perform real-time chemical analyses at sea and conduct more experimental 

 studies at sea. A great deal of chemical oceanography has used ships as sampling platforms and 

 returned the samples to shore laboratories for analysis. However, important investigations of 

 chemical speciation and transient chemicals frequently can not be accomplished on stored 

 samples. Future marine chemical studies will require analytical and experimental facilities at 

 sea that equal those on land. 



C. Marine Geology and Geophysics. Marine geoscience in the next decade will focus on: 



• Close-up investigations of seafloor features with 3-D imaging, detailed measurements and 



sampling with manned submersibles, deeply-towed vehicles, and remote deep-swimming 

 devices; and 



• More powerful geophysical techniques for imaging the deep structure of the oceanic crust, 



margins, and lithosphere. 



This research will require use of research vessels designed specifically for studying seafloor 

 geology. The specialized instrument systems and activities that most profoundly influence the 

 designs are: 



• Large array multichannel seismic system: requires rigging for handling large air gun 

 arrays and large, reinforced deck space aft to accommodate a 20-ton, 8-foot 



high, 15-foot wide streamer reel. The ability to tow multiple air gun arrays and/or 

 streamers over a 50 to 100 meter thwartship span is important. The air guns require a 

 minimum of four large capacity compressors that can develop pressures of >2,500 psi. 



• Deeply-towed acoustic imaging system: requires a winch capable of handling 25,000 feet 

 of electro-mechanical cable. 



• Multibeam bathymetry: requires a "quiet" hull, sufficient beam to carry the 



hull-mounted hydrophone arrays, and, for some applications, a relatively high cruise 

 speed (15 knots). 



• Submersible: One or more of the geological ships should be able to carry and launch a 



manned deep submersible (e.g., Alvin). 



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