Seismicity of the ocean-basin floor 80 Ocean-basin floor provinces and crustal structure 80 Mid-oceanic ridges 83 Definition 83 Mid-Atlantic Ridge 83 Provinces of the Mid-Atlantic Ridge 84 General statement 84 Crest provinces 84 Flank provinces 95 Azores Plateau 97 Azores-Gibraltar Ridge 98 Atlantis-Plato-Cruiser-Great Meteor Seamount Chain 98 Geology and geophysics of Mid-Atlantic Ridge physiographic provinces 98 Seismicity of the Mid-Atlantic Ridge 98 Sediments and physiographic provinces of the Mid-Atlantic Ridge 99 Rocks of the Mid-Atlantic Ridge 99 Crustal structure of the Mid-Atlantic Ridge provinces 100 Origin of the Mid-Atlantic Ridge 103 Sub-bottom reflections recorded on PDR records and physiographic provinces 05 Summary of province characteristics 107 BIBLIOGRAPHY 109 INDEX 115 ILLUSTRATIONS PLATES FOLLOWING PLATE 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