70 • Marine Minerals: Exploring Our New Ocean Frontier 



Figure 2-10.— Potential Hard Mineral Resources of the Hawaiian EEZ 



Cretaceous 

 seamounts 



Necker 

 Ridge 



Horizon Guyot 



Cretaceous 

 seamounts 



500 



Johnston Island 



1000 Miles 



Seamounts 





Palmyra Reef 

 Kingman Atoll 







SOURCES: Office of Technology Assessment, 1987; U.S. Department of the Interior, "Symposium Proceedings— A National Program for the Assessment and Develop- 

 ment of the Mineral Resources of the United States Exclusive Economic Zone," U.S. Geological Survey Circular 929, 1983. 



tively free of sediment or are covered with fine sedi- 

 ment consisting of red clay and/or calcareous ooze. 

 The extent to which the United States has juris- 

 diction over the EEZs of the various Trust Terri- 

 tories (figure 2-11) is examined in appendix B. 



Cobalt-Ferrotnanganese Crusts 



Recently, high concentrations of cobalt have been 

 found in ferromanganese crusts, nodules, and slabs 

 on the sides of several seamounts, ridges, and other 

 raised areas of ocean floor in the EEZ of the cen- 

 tral Pacific region. The current interest in cobalt- 

 enriched crusts follows an earlier period of consid- 



erable activity during the 1960s and 1970s to de- 

 termine the feasibility of mining manganese nod- 

 ules from the deep ocean floor. While commercial 

 prospects for deep seabed nodule mining have 

 receded because of unfavorable economics com- 

 pounded by political uncertainties resulting from 

 the Law of the Sea Convention, commercial inter- 

 est in cobalt-ferromanganese crusts is emerging. A 

 number of factors are contributing to this shift of 

 interest, including seamount crusts that: 



1 . appear to be richer in metal content and more 

 widely distributed than previously recognized, 



2. are at half the depth or less than their abyssal 

 counterparts. 



