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METHODS OF EXPLORING THE OCEAN FLOOR 

 Robert S. Dietz 



INTRODUCTION 



Oceanography is the geoscience which is concerned with the hydrosphere 

 plus the water-air interface and the water-lithosphere interface. The subject of 

 this paper is the instrumentation for studying this last-named interface -- the 

 sea floor. In order to restrict the subject matter, discussion will be limited to 

 those methods which are used to study the sea floor in a strict sense and not 

 those which are used to study processes acting on or along the bottom such as 

 bottom-mounted current meters, turbidity meters, suspended load samplers, 

 etc. Also, it will be limited to devices which can be used in moderate to deep 

 water thus eliminating from consideration such shallow water devices as bottom 

 augurs, pile-driver corers, etc., which belong to the stiff-handled group of bot- 

 tom samplers to which energy can be applied at the surface. This also will ex- 

 clude those devices which require operation by a diver. 



Methods of exploring the bottom can be conveniently divided into three 

 groups, viz.: (1) direct sampling of the bottom, (2) obtaining bottom informa- 

 tion acoustically, (3) visual examination. 



DIRECT SAMPLING OF THE BOTTOM 



General - Omitting apparatus for specialized purposes, most bottom samplers 

 can be classified as corers, dredges, grab samplers, and underway samplers. 

 These are the standard or "classical" methods of studying the bottom. Consid- 

 erable progress has been made in such methods since the subject was summar- 

 ized by Hough (1939). Hough's paper contains an excellent list of references. 



Coring - Various methods of supplying energy to core barrels have been at- 

 tempted, such as using explosive charges, but to date none have proved as suc- 

 cessful as simply using the freefall or dead drop of a heavily weighted core tube. 

 The early types of corers were small and of light weight so that they rarely ob- 

 tained a core more than a few feet in length. By increasing the weight, using 

 an optimum core tube diameter, and making various other changes Emery and 

 Dietz (1941) were able in 1940 to take cores up to 17 feet long representing a 25 

 foot section of the sea floor with a 600 pound core tube. This represented 

 about the miaximum length of core that could be obtained with a simple gravity 

 corer because the wall friction of the sediment plug in the core barrel prevented 

 any additional material from entering the tube. Hvorslef and Stetson (1946) 

 made additional improvements, one of which was the addition of a tripping arm 

 which allowed the free fall of a corer lowered slowly to the bottom. 



KuUenberg (1947) made a great improvennent on corers by having the 

 core tube fall over a piston. This keeps the nose of the tube from becoming 



