or indirectly. In practice it is convenient to divide this general 

 field into (l) Submarine Topography, (3) Sedimentation, and (3) 

 Submarine Dynamics. 



1. Submarine Topography 



Knowledge of the topography of the basins that enclose the 

 oceans is the rational introduction to the science of Oceanography, 

 because this is the factor that determines the extent, shapes, and 

 depths of the oceans, which in turn largely control the whole gamut 

 of thermal, circulatory and biological phenomena in the sea. This 

 knowledge is equally needed by the geologist for (as often stated), 

 all advances in the specific field of submarine geology must be 

 founded thereon, while it is equally basic to our understanding of 

 some of the most pressing problems of general geology, for we see 

 here the modes and results of the earth's deformations in past ages. 



In connection with the leading question concerning the strength 

 of the earth* B crust, for example, much more sounding is needed in 

 such submarine hollows as the Tonga, Kermadec, and Porto Rico deeps, 

 which bid fair to indicate the actual strength of the crust, and the 

 degree of stability of mountains and plateaux. In the same way, an 

 exact knowledge of the topography of the bottom would establish the 

 possibility of great rock-slides on the steeper submarine slopes - 

 a problem recently raised by puzzling rock formations in the Alps, 

 Appalachians, and other mountain chains, "The bearing of submarine 

 mapping and its geologic interpretation on the discovery of regions 

 of submarine volcanoes, and areas of earthquake displacements must," 

 to quote from Doctor David White's statement to the U. S. Naval 

 Conlerence on Oceanography, 1926, "be obvious to all," Fuller know- 

 ledge of the shape of the bottom should, as he has emphasized, dis- 

 close the locations where many of the great earthquakes originate; 

 they should also disclose the centers of submarine vulcanism where 

 islands may now be building up or the reverse. 



Better information on the depth, especially as regards droximed 

 valleys, etc., would also afford data for deducing the minor changes 

 of position of shorelines, and for estimating the amount of material 

 removed from the land surfaces by the various processes of erosion. 

 In this connection we need to know hov7 deep wave-base is, and how 

 effective waves and currents actually are, as scouring forces 

 (Page 32), Until we know more about the exact depths we can not 

 hope to understand the origin and history of the thousands of oceanic 

 islands, or the remarkable events that led to the formation of such 

 islands as the Hawaiian, or Samoan. 



The Ooral Reef problem - a hardy-perennial controversy - is also 

 as much a question of submarine geology as of biology, or more, 

 because of the fact that the up- growth of these peculiar lime forma- 

 tions depends on a complex interaction of physical and chemical 

 factors, in which temperature, salinity, currents, the absolute depth 

 risings or sinkings of the bottom, and possible changes of sea level, 

 all play a part. 



In considering the origin of any given reef, as well as in the 

 general reef problem, the submarine topography of the island or 



