II. TOPOGRAPHY AND STRUCTURE 



12. TOPOGRAPHY OF THE DEEP-SEA FLOORi 



Bruce C. Heezen and H. W. Menard 



1. Introduction 



In The Oceans, Sverdrup, Johnson and Fleming (1942) state that, "from the 

 [purely physical] oceanographic point of view, the chief interest in the topo- 

 graphy of the sea floor is that it forms the lower and lateral boundaries of the 

 water. The presence of land barriers or submarine ridges that impede a free 

 flow of water introduces special characteristics in the pattern of circulation and 

 in the distribution of properties and organisms." On the other hand, the geo- 

 morphologist is concerned primarily with the distribution and dimensions of 

 the topographic features that occur on the submerged portions of the Earth's 

 crust. The physical oceanographer views the sea floor as simply a bottom to 

 the receptacle within which the pcean water rests ; in contrast, the geologist's 

 interest in topography is in what it can tell him concerning the geological struc- 

 ture, the erosional and dejjositional and tectonic history, and the origin of the 

 ocean basins and their relief. Thus, attitudes, objectives and the systems of 

 nomenclature used by these two groups differ widely. 



The physical oceanographer divides the ocean into a series of broad basins 

 separated by ridges. These basins are generally defined by the contours shown 

 on the General Bathymetric Chart of the Oceans at a scale of 1 : 10,000,000. 

 A map of ocean basins is essentially a map showing boundaries which lie along 

 the crests of all major ocean ridges and along the margins of all land-masses 

 (Wiist, 1940 ; see also Fig. 1). All the water contained in the depression between 

 the land and the crest of a prominent ridge is considered to lie in a certain 

 basin. One cannot deny the need and the usefulness of such a system, particu- 

 larly in regard to problems of physical oceanography (Wiseman and Ovey, 

 1954, 1955). But this crude "bathymetric system" of classification is poorly 

 suited to studies of submarine physiography, for the generalized bathymetric 

 contours, on which the bathymetric system is based, cut across physiographic 

 units with little regard for physiograpliic boundaries determined by a detailed 

 study of the relief of the sea floor (Heezen et al., 1959 ; see also Fig. 2). 



The development of a new physiographic outlook toward submarine relief is 

 the major advance in submarine topography since The Oceans was written. 

 Physiograpliic studies of sea-floor relief were made possible by the development 

 and wide use of continuous-recording echo-sounders. With the exception of the 

 magnificent work done by the Meteor Expedition (Maurer and Stocks, 1933), 

 no detailed profiles of the deep-sea floor were available prior to World War II. 



1 LaiTiont Geological Observatory (Columbia University) Contribution No. 592. 

 [MS received July, 1960] 233 



