Soundings in the northeast Atlantic compiled by the British Admiralty Hydrographic Department were kindly provided by Cmdr. J. S. N. Pryor of that organization. Dr. M. N. Hill of Cambridge and Dr. G. E. R. Deacon of the (British) National Institute of Oceanography were instrumental in obtaining many of these valuable deep-sea soundings. Original sounding sheets of many areas were provided by the Coast and Geodetic Survey through the courtesy of Admiral A. Karo and Mr. G. F. Jordan.

B. Luskin's development of the Precision Depth Recorder and his continued research and development in echo-sounding equipment made it possible to obtain many of the detailed data of this paper.

The following expedition chief scientists conducted sounding surveys which have been incorporated in this paper: M. Ewing, J. L. Worzel, J. E. Nafe, I. Tolstoy, R. S. Edwards, G. R. Hamilton, C. L. Drake, B. Luskin, W. C. Beckmann, F. Press, J. Northrop, J. Hirshman, M. J. Davidson, R. J. Menzies, F. C. Fuglister, E. T. Miller, and B. C. Heezen.

The writers are grateful to the great number of scientists who encouraged them in this work and especially to those who offered suggestions and discussed the data and conclusions. We are particularly indebted to W. H. Bucher for discussions relative to tectonics, to David B. Ericson for problems relating to sediment distribution and analysis, and to C. O'D. Iselin and C. H. Elmendorf for general encouragement and support during the several years of this study.

CONTENTS

PAGE
Abstract[1]
Part 1. Preparation of the Physiographic Diagram[3]
Part 2. Physiographic Provinces[11]
Introduction[11]
Nomenclature and classification of deep-sea relief[11]
Units of depth and slope[12]
Continent and ocean[16]
Continental margin[17]
Definition and general categories[17]
General categories[17]
Category I provinces[17]
Category II provinces[18]
Category III provinces[19]
Regional description of continental margin[21]
Benches and terraces of the continental margin[41]
Geology and geophysics of continental-margin physiographic provinces[51]
Seismicity of the continental-margin provinces[51]
Magnetic anomalies and continental-margin physiographic provinces[51]
Crustal structures and continental-margin provinces[52]
Sediment distribution and physiographic provinces of the continental margin[53]
Past, present, and future of the continental-margin provinces[53]
Ocean-basin floor[55]
General description[55]
Abyssal plains[55]
General discussion[55]
Regional description[57]
Abyssal hills[61]
Definition and distribution[61]
Regional description[63]
Origin of abyssal-hills topography[65]
Other major features of the abyssal floor[66]
Abyssal gaps[66]
Mid-ocean canyons[66]
Regional description[66]
Origin of abyssal-floor topography[74]
Oceanic rises[74]
Definition and distribution[74]
Regional description[74]
Seamounts of the ocean-basin floor[78]
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[9]5
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[105]
Summary of province characteristics[107]
Bibliography[109]
Index[115]