TEST B: UNDERWATER EXPLOSION 



smooth, but was found to contain several secondary 

 craters.* 



The majorit.y of the materials torn out settled to 

 the bottom within a few hours, forming a thick struc- 

 tureless carpet. But thousands of tons of sediment re- 

 mained in suspension. Even after two weeks, the water 

 still carried a mineral load. Some bottom material had 

 been thrown high into the air ; some of it fell onto the 

 decks of target vessels. 



A large number of fish were killed in the corner of 

 the lagoon where the explosion occurred. Elsewhere in 

 the lagoon the fish survived, and outside the atoll the 

 fish were practically unaffected either by the explosion 

 or the subsequent radiological effects.! 



* The depth of the bottom crater was computed from very ac- 

 curate sou7idings made before and after the explosion. The soimd- 

 ings were made by members of the Oceanographic Group operating 

 from, the hydrographic survey ship BOWDITCH. An ingenious 

 but unsuccessfid attempt was made to measure the exact diameter 

 of bottom area laid bare by the explosion. Some days before the 

 explosion, the Group laid long steel cables on the bottom near the 

 Zeropoint, and to these cables they attached a large number of hol- 

 low steel cylinders containing unexposed photographic film. It was 

 expected that in those areas where the water was swept clear, gamma 

 radiation from the underwater fireball would reach the cylinders 

 and affect the film. Unfortunately, the explosion was so violent that 

 none of the cylinders were ever seen again. 



t Over 40,000 atoll fish were caught. Several new types were 

 found. Professional fishermen recruited from the west coast fishing 

 industry caught many tons of tuna and other deep sea fish (pelagic 

 fish). Unfortunately, 98 percent of these latter were lost when 

 YP-636 went aground thirty miles south of San Francisco in Sep- 

 tember, 1946. 



163 



