DIVE NO. 61 



Man's first direct viewing of the sea floor at 18, 150 

 feet was achieved on this dive, which brought the manned 

 deep- diving record back to the U. S. Upon landing, the 

 bottom was noted to be uniformly level, but pock-marked 

 with numerous white circular areas on a tawny substrate 

 (fig. 9). Closer examination revealed that biological 

 activity was responsible for these marks. The lighter sub- 

 surface sediment had obviously been brought to the surface 

 by burrowing animals. The sediment had subsequently 

 spread circumferentially about the penetration without 

 creating a mound. The bearing strength of the sea floor 

 was adequate to sustain the weight of the bathyscaph satis- 

 factorily. Maximum penetration was estimated to be no 

 more than 3 inches. 



Figure 9 illustrates the numerous particles that were 

 present in the water immediately above the bottom. Bio- 

 logical entities and suspended particles above the sea floor 

 were conspicuous and a definite turbid condition existed. 

 The brownish tinge of the sea floor was thought to be caused 

 by the settling of the inanimate materials and organic sub- 

 stances present in the water mass directly above the bottom. 



The sea floor downgrade slope was evident and esti- 

 mated to be about 1 degree. Upon leaving the sea floor, 

 the observers noted a vertical drop of 4 to 5 feet that inter- 

 rupted the gentle slope to form a "berm" running perpen- 

 dicular to the downslope gradient. Beyond this drop, the 

 sea floor appeared to have approximately the same depres- 

 sion angle. The upper discontinuity of the break in the 

 slope clearly revealed an exposed rock outcrop. Maximum 

 exposure of rock was 6 inches. 



Evidence of ripple marks or scouring formations was 

 absent. The funnel-shaped depressions and/or volcano- 

 shaped mounds found at shallower depths and at all loca- 

 tions where bathyscaph operations had been previously 

 conducted were absent. Water current was negligible and 

 apparently had been in recent time insufficient to produce 

 ripple marks or contribute significantly to the alteration 

 of the microrelief. A few pebbles, about 0. 5 inch in 

 diameter, similar to those seen at 4900 feet, were scattered 

 irregularly throughout the area. 



Upon leaving the bottom, it was possible to see that the 

 sphere had been supported during the bottoming by a ridge 

 of exposed rock 8 to 10 feet long. 



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