184 OCEANOGRAPHY IN THE UNITED STATES 



oratory. The Baird is an ex-Navy tug altered for the purposes of 

 reseaT'ch, and is operated by Scripps. It is with ships such as these 

 that we have been exploring the oceans. Even now, the Vema is on the 

 return leg of an exploratory and scientific cruise which has carried 

 her completely around the South American Continent, while the Baird 

 is Avorking in the Gulf of California. 



From these exploratory cruises, which have been designed to work 

 on particular problems, has come a general understanding of several 

 broad features of the oceans. 



We now understand better the general circulation of the oceans 

 wdiich is the controlling factor in the distribution of marine life, phys- 

 ical and chemical characteristics of the water, the movement of some 

 of the sediments and some of the temperature characteristics. A 

 knowledge of the distribution of marine life is important to the Navy 

 since myriads of forms of marine animals are noise makers and pro- 

 vide an important share of the background noise of the sea. This noise 

 often interferes with our efficient use of acoustic detection equipment 

 and mystifies those who listen, in the oceans, for passing submarines. 

 We know now the general distribution of lone mountains sticking up 

 toward the surface of the sea which we call sea mounts. Coupled with 

 this we have located features of the mid- Atlantic ridge, a submarine 

 mountain range running from 60 degrees north to 60 degrees south 

 down the middle of the Atlantic Ocean, and we have discovered a com- 

 parable but larger range in the Pacific called the mid-Pacific Moun- 

 tains which stretch from Hawaii toward Kamchatka and southerly 

 toward the Tuamotu Archipelago. As a part of the bottom studies, 

 we have learned of the distribution of bottom sediment types such 

 as clays, sands, manganese nodules and rocks. These features are 

 important for their applicability to submarine navigation and their 

 usefulness in laying out deep diving programs of a more extensive ex- 

 ploratory nature. 



As I have indicated, these exploratory cruises are specifically pro- 

 gramed to investigate special problems. Each cruise is led by a chief 

 scientist on board the ship wlio has priority for his work over any 

 other general oceanographic work which may also be accomplished. 

 Out of this type of program have come the answers to specific ques- 

 tions which I would like to mention next. 



A large portion of our oceanographic program is involved with a 

 special field which, for lack of a better term, we call marine geo- 

 physics. This field encompasses the measurement at sea of the follow- 

 ing earth features : 



{a) The earth's magnetic field : 

 (h) The earth's gravity field; and 



[c) The structure of the earth beneath the ocean (which I 

 would especially like to mention). 



The earth's structure is measured in several ways, the most impor- 

 tant being seismic. Seismic work at sea is accomplished by two 

 ships one of which detonates an explosion, ranging in size from 2 to 

 800 pounds of TNT, while the other ship, miles away, records the 

 sound as it is reflected and refracted by the bottom structure. From 

 this work we have proved that there is no granite under the sea floor 

 as there is under the continents. We have learned that the earth's 

 crust under the oceans is relatively thin as compared to tlie crust of 



