Searching the shelf 

 for geologic clues 



Sea Hunt 



BY SARAH FRIDAY 



Stan Riggs, Scott Snyder and 

 Al Hine are on a treasure 

 hunt. The loot is not gold 

 coins or precious jewelry. 

 These Sea Grant geologists are 

 searching the bottomlands off 

 North Carolina's coast for reef- 

 type structures that hold a wealth 

 of natural resources. 



The structures, called "hard- 

 grounds," lie anywhere from just 

 beyond the shoreline to the edge of 

 the continental shelf throughout 

 the East Coast. These underwater 

 mesas occur in association with 

 sediments rich in heavy minerals 



and phosphate. In addition, they 

 serve as attachment sites for food 

 sources for fish. 



For their research, the team 

 chose Onslow Bay as a study site. 

 "Most of Onslow Bay is a hard- 

 ground with very little sand on it," 

 says Riggs. "What we're trying to 

 do is understand what are the dif- 

 ferent kinds of hardgrounds? 

 Where do they occur? What is their 

 geologic nature?" 



With this information, Riggs be- 

 lieves the researchers will be able 

 to tell why certain hardgrounds 

 attract more organisms than others. 

 And in the long run, he hopes that 

 the sediments, or substrate, where 

 these hardgrounds develop can be 

 made more productive. 



Riggs believes that someday it 

 may be possible to "plow" the shelf 

 floor to build ridges of rock above 

 the abrasive flat sands. These ridges 

 will create more outcroppings that 

 attract flora and fish, much like 

 artificial reefs do today. 



"We can modify the land to pro- 

 duce crops," says Riggs. "That's 

 what agriculture is. Man has learn- 

 ed how to manipulate the soils, 

 tend the soils. And it's no different 



Scarps like this on the underwater mesas of Onslow Bay collect a variety of corals, other organisms and, eventually, fish 



