ILLUSTRATIONS
Reading edition
PLATES
PLATE FOLLOWING PAGE
1. Physiographic diagram: Atlantic Ocean, Sheet 1 (In separate tube)
2. Preliminary chart of Hudson Submarine Canyon 20
3. Representative PDR records from continental rise of northeastern United States 32
4. PDR records from continental slope and Blake Plateau 32
5. PDR records from outer ridge east of the Blake Plateau and from the Blake-Bahama Abyssal Plain 32
6. PDR record of outer ridge showing sub-bottom horizon 32
7. Tracings of PDR records across continental slope and part of the Blake Plateau 36
8. PDR records European continental rise and Biscay Abyssal Plain 38
9. Representative PDR records of continental margin and abyssal floor southwest of Canary Islands 38
10. PDR record of abyssal hills, southeast of Bermuda Rise 38
11. Ocean bottom photographs of the continental margin and ocean basin floor 38
12. PDR record of Biscay Abyssal Plain 52
13. PDR records of Madeira Abyssal Plain and the Madeira Rise 52
14. PDR records of Mid-Ocean Canyon No. 2 and canyons at Vema Gap 58
15. Ocean-bottom photographs of seamounts 58
16. Representative PDR records from Bermuda Rise 78
17. PDR record, Bermuda Scarp Zone 78
18. PDR record, Upper Step Mid-Atlantic Ridge 78
19. Ocean-bottom photographs; Mid-Atlantic Ridge 78
20. Physiographic provinces, Atlantic Ocean 122
21. Control chart 122
22. Six trans-Atlantic topographic profiles 122
23. Index chart showing locations of profiles of Plates 24, 25, 26 and Figure 45 122
24. Thirty-four profiles of the continental margin: western North Atlantic 122
25. Twenty-three profiles of the continental margin of Europe and Africa 122
26. Crustal structure and continental-margin provinces 122
27. Five topographic profiles, western North Atlantic 122
28. Distribution of deep-sea sands in relation to physiographic provinces 122
29. Earthquake epicenters, North Atlantic 122
30. Location of PDR records and bottom photographs reproduced as illustrations. 122
FIGURES
FIGURE PAGE
1. Method of preparation of physiographic diagram 4
2. Precision depth recorder (PDR) sounding lines obtained by research vessels 6
3. Good, but nonprecision sounding lines obtained by research vessels 7
4. Major basins of the North Atlantic, after Wüst (1940) 12
5. Sound-velocity corrections for echo soundings 13
6. Conversion diagram for degrees, per cent grade, feet per statute mile, and gradient 14
7. Gradients from 1:5 to 1:8000 shown at 40:1 vertical exaggeration 15
8. Outline of submarine topography 15
9. Major morphologic divisions: North Atlantic Ocean 16
10. Three categories of continental-margin provinces 17
11. Two east-west profiles of Southeast Newfoundland Ridge 22
12. Laurentian Channel 23
13. Eastern Channel, Gulf of Maine 23
14. Submarine canyons off the Scotian Shelf 24
15. Continental-margin provinces: Type profile off northeastern United States 26
16. Tracings of PDR records of continental and insular slopes 28
17. Cross sections of Hudson Submarine Canyon 32
18. Tracing of PDR record of Blake Escarpment 34
19. Continental-margin provinces: Type profiles off northwest Africa 40
20. Georges Bank canyons 44
21. Two projected profiles of Georges Bank canyons 45
22. Geologic section at Cape Hatteras, Virginia 46
23. Correlation of structural benches off northeast United States 48
24. Geologic section: Western Europe based on refraction measurements 49
25. Index chart, location of abyssal hill profiles illustrated in Figures 26 and 27 62
26. Eleven profiles, Abyssal Hills Province, western Atlantic 62
27. Eight profiles, Abyssal Hills Province, eastern Atlantic 63
28. Tracing of PDR record, abyssal hills, southeast of Bermuda Rise 64
29. Northwest Atlantic Mid-Ocean Canyon 67
30. Eight east-west profiles showing Northwest Atlantic Mid-Ocean Canyon 68
31. Forty-eight cross sections of Northwest Atlantic Mid-Ocean Canyon 69
32. Long profile of Northwest Atlantic Mid-Ocean Canyon 70
33. Tracing of PDR record across Theta Gap 73
34. Natural scale profile, Kelvin Seamounts 77
35. Crustal sections in various physiographic provinces, determined by seismic-refraction measurements 81
36. Index to natural-scale Mid-Atlantic Ridge profiles reproduced in Figures 37-41 84
37. Natural-scale Mid-Atlantic Ridge profile 1A 85
38. Natural-scale Mid-Atlantic Ridge profile 1B 86
39. Natural-scale Mid-Atlantic Ridge profile 1C 87
40. Natural-scale Mid-Atlantic Ridge profile 2A 88
41. Natural-scale Mid-Atlantic Ridge profile 2B 89
42. Type profile, provinces of the Mid-Atlantic Ridge 90
43. Tracing of PDR record, Rift Valley, Rift Mountains, High Fractured Plateau, and Upper Step 91
44. Tracing of PDR record, Western Rift Mountains 92
45. Twenty-six rift valley profiles, Mid-Atlantic Ridge 93
46. Five representative profiles, crest and western flank of Mid-Atlantic Ridge 94
47. Axial profile of the Mid-Atlantic Ridge 96
48. Profile of total magnetic intensity and topography, Mid-Atlantic Ridge 101
49. Physiographic provinces and trans-Atlantic structure 102
TABLES
TABLE PAGE
1. Characteristics of continental rise, northeastern United States 27
2. Characteristics of continental rise, northwest Africa 41
3. Depths of prominent continental-shelf terraces 42