200 



Sylvania Seamount giving evidence of an extensive manganese deposit; (3) Deep 

 ripple marks, scours, etc. , have established the existence of currents in the 

 ocean at greater depths than was hitherto known; (4) Much information has been 

 obtained on the ecology of bethonic life; (5) Much information has been obtained 

 on bottom structures such as tracks, burrows, etc. , which are useful in estab- 

 lishing paleo-ecologic criteria regarding the depth and environment of deposition 

 of sedimentary rocks. Further work with the camera should reveal the pres- 

 ence of minor erosional forms, such as gullies, and the detailed character of 

 submarine canyons and deep sea channels. It seems to the writer that, in the 

 long run, more information will be obtained on the nature and importance of bot- 

 tom currents by photographing the bottom than by any method of direct measure- 

 ment of bottom currents. One also can hope that bottomi photography might de- 

 tect a turbidity current in actual operation. 



Finally, with the camera in a watertight housing and the monitor on the 

 deck of a ship, underwater television offers a promising method of exploring the 

 ocean floor. Development of the small industrial nnodel television camera with 

 the Vidicon tube, which permits the use of a small housing, is especially hopeful. 

 Because of line losses and because of the infeasibility of lowering conductor 

 cables to great depths, TV must remain, for the present, a method applicable 

 only to continental shelf depths. Underwater TV was first used in the 1947 re- 

 survey of Bikini Atoll (Engleman) but the great utility of the method was first 

 forcibly demonstrated by the identification of the sunken submarine Affray in the 

 English Channel by the British in 1951. 



DISCUSSION: Bruce C. Heezen* 



Of the methods of exploring the ocean floor discussed by Br. Dietz, the 

 ones presently producing the bulk of the useful data are echo sounding, coring, 

 dredging and undersea photography. Most urgently needed in connection with 

 these techniques is the development for general use of accurate echo sounder 

 recorders of high resolution and the development of fast reliable winches which 

 could be available to the major research and survey vessels. 



The development of recording echo sounders able to record in depths 

 greater than 2000 fathoms came during World War II with the modified NMC mod- 

 els. More recently the EDO echo sounder has been developed incorporating 

 many electronic improvements. As Dietz has pointed out, the 0-6000 fathom 

 scale of the EDO instrument is of little use to the geologist or hydrographer, and 

 miost of us have made the required changes to convert the EDO recorder for mul- 

 tiple 600 fathom scale recording. However, the quality of this type of EDO rec- 

 ord is far from satisfactory. It has been found in three recent cruises of the 

 R/V ATLANTIS and R/V ALBATROSS III that the stylus speed of at least two in- 

 dividual sets, when operated on a precision a.c. power supply, is about 2.5% fas- 

 ter than the stated standard velocity of 4800 feet per second. Other errors are 

 caused by stylus belt bounce and by fluctuations of the zero line. Vast flat, near- 

 ly level plains have been found in the deeper parts of the Atlantic Ocean and prob- 

 ably occur in all of the oceans. The slopes of these "abyssal plains" probably 

 range from less than 1 to 10 feet per mile. In order to study these areas the de- 

 velopment of a sounder which in any depth accurately records to 1 fathom or bet- 

 ter is urgently needed. ** 



* - Contribution No. 98 from the Lamont Geological Observatory. 



** - Since the Rancho Santa Fe Conference such a recorder has been devel- 

 oped, tested at sea and is now in general use on Lamont Geological Observatory 

 cruises (Luskin, Heezen, Ewing and Landisman, in press). 



