of large rigid plates moving relative to each other, provides a basis 

 for estimating the composition and structure of the sea floor in areas 

 where direct measurements are sparse or lacking. Reliability of the 

 predictions will improve as the theory is extended and refined. 



A technique for locating those portions of a midocean ridge for 

 which the Navy needs bathymetric data has been developed using an 

 airborne magnetic anomaly detector. Fracture zones over the 

 midocean ridges follow definite patterns that are dependent on the 

 present and past motions of oceanic crustal plates. The numerous 

 fracture zones that cross the mid-Atlantic Ridge are of interest to 

 anti-submarine warfare community. Mapping of fracture zones from 

 a surface vessel in the highly complex and variable terrain found 

 along the axis of the mid-Atlantic Ridge is a difficult and time- 

 consuming task. The fracture zones, however, are characterized by 

 distinct high amplitude magnetic anomalies that may be readily 

 mapped using airborne magnetometers. 



In the study of the mid-Atlantic Ridge, a Navy research aircraft 

 was used to carry out aeromagnetic studies with a close grid pattern 

 over the ridge. The magnetic anomalies were used to determine the 

 location and direction of the fracture zone lineations. A research ship 

 was then directed to the exact location of the fracture zones to obtain 

 detailed subbottom profiles and other geophysical data associated 

 with the fractures. The study demonstrates conclusively that in 

 areas of complex bottom topography an airplane and research ship 

 combination is an excellent technique to use in charting sea floor 

 tectonic patterns. 



Studies of the gravity and geomagnetic fields over the Arctic 

 Ocean and environs have been sponsored by the Navy. The gross 

 magnetic field has been defined over the Arctic Ocean Basin and 

 adjacent seas. This information assesses the relative success 

 potential for using standard magnetic submarine detection devices 

 in various geographic regions. Magnetic data also provided 

 additional information concerning the Alpha Ridge and the Nansen 

 Ridge. These two transoceanic submarine mountain chains are 

 important factors for underwater acoustic surveillance systems. 

 Gravity studies have provided the data base for what knowledge we 

 have of the geopotential surface in the Arctic, which influences 

 inertial guidance and navigationsystems and ballistic trajectories. 



Magnetic and gravity data combined have been the major 

 contributors to developing a hypothesis for the origin and 

 morphology of the Arctic Ocean Basin. With this hypothesis we can 

 now predict, to a first-order approximation, environmental factors 

 important to naval operations, such as topography, sea floor 

 roughness, and sediment cover, in unsurveyed or unsurveyable 

 areas of the Arctic Ocean. 



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