1998 Year of the Ocean Ocean Energy and Minerals 



mammals, and freely floating marine invertebrates. Mooring turbines in open water rather than 

 attaching them to dams, and placing streamlined protective housings around the turbine blades, 

 greatly reduces these adverse environmental impacts. The consequent reduction in energy 

 efficiency adds to their cost; nonetheless, many engineers still believe that these systems are 

 commercially viable. 



MINERAL RESOURCES 



A wide variety of mineral resources are found on the seafloor. These resources fall into 

 four general categories: 



• granular sediments 



• placer minerals 



• hydrothermal deposits 



• hydrogenetic minerals 



Granular sediments are transported to the sea by rivers and glaciers and are sorted 

 according to size by wave action on the coastline. They include quartz-rich sand and gravel, 

 carbonate-rich sand, shell, silt, and clay. Gold, diamonds, platinum, tin, and titanium are among 

 the most common placer minerals, as well as concentrations of heavy minerals and ores such as 

 titanium oxide. Hydrothermal minerals are associated with volcanic activity and include sulfide 

 deposits rich in copper, zinc, lead, gold, and silver. Hydrogenetic deposits form by precipitation 

 from seawater under various conditions and host minerals such as phosphorite, salt, barite, and 

 iron-manganese nodules, and crusts rich in cobalt, platinum, nickel, copper, and rare earth 

 elements. 



Both coarse sand and gravel and finer sand are extremely abundant on most continental 

 shelves, with the coarsest materials (gravels) occurring closest to the coast and finer grained 

 materials dominating the outer shelves and slopes. The thickest sand and gravel deposits are 

 those formed as a result of glacial action in the northern and southern thirds of the globe. Placer 

 minerals are also found nearest to the coast, usually in association with present or former river 

 systems. Marine hydrothermal minerals are found in the deep ocean volcanos on oceanic ridges 

 and island arc systems. Hydrothermal deposits form in association with underwater vents of 

 mineral-rich hot water called "smokers.". Hydrothermal deposits also include phosphorite and 

 barite accumulations on the continental shelves. The cobalt-rich manganese crusts found on the 

 flanks of most of the 50,000-plus extinct volcanic seamounts in the Pacific Ocean are 

 hydrogenetic deposits. 



Sand and Gravel 



Sand and gravel, used primarily for construction aggregates, constitute the largest 

 tonnage of any ocean mineral produced. These materials are essential resources for the expanding 

 populations of coastal areas. Aggregates are used in nearly all residential and commercial 



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