SECT. 1] 



CONTINUOUS REFLECTION PROFILING 



59 



2000 FT 



DEPTH 



IN 100 

 FEET 



200 



300 

 400 

 500 

 600 

 700 

 800 



100 



200 



300 

 400 

 500 

 600 

 700 

 800 



Fig. 9. The continental shelf from a commercial survey off California. (After Officer.) 



C. Intermediate Water Depths 



Reconnaissance piotiles have been made by Woods Hole groups in the 

 Mediterranean Sea to the northwest of the Strait of Messina, and in the 

 North Atlantic on the Blake Plateau. Near the Strait of Messina the results 

 suggest sediment-filled channels trending to the northwest downslope from the 

 Strait (see Fig. 11). In these channels sediments attain a thickness of a thousand 

 feet or more in places where the water depth is over 1200 ft. On the Blake 

 Plateau flat-lying beds at shallow depths below the bottom were indicated. 

 Profiles from the shelf-edge to abyssal depths have revealed outcrops on the 

 continental slope of Europe and North America and layering over 1 km thick 

 beneath the continental rise off eastern North America. 



D. Deep-Ocean Studies 



During some early tests in 1956, a Woods Hole group recorded apparent sub- 

 bottom reflections with a spark source in water over 2640 fm deep. This could 

 be done only from a ship lying to and on silent ship routine. More recently, 

 Ewing and Tirey (1961) have reported extensive reflection proflling in the deep- 

 sea in 1960 with explosives, while Hersey (1962) reported similar observations 

 with a boomer in 1961. Since that time many thousands of miles of reflection 

 profiling (with 0.5 lb of explosives) have been recoiled from Vema of Lamont 

 while, from Chain of Woods Hole, both boomer (5000, 9000, and 13,000 joules 

 electrical storage) and sparker (25,000 joules) have been used in selected 

 locations in the North Atlantic Ocean and the Mediterranean Sea. 



Examples of somewhat contrasting structures are shown in Figs. 12-15, 

 taken from various studies on Chain. A thick section, presumed to be hori- 

 zontally stratified sediments in the abyssal plain west of Gibraltar, is shown in 

 Fig. 12. Fig. 13 shows a long section across the low rise surrounding Madeira 



