REGIONAL MAGNETISM 



SUBMARINE CANYON 



DIVERGENCE OF 

 ORTHOGONALS 

 PRODUCES LOW 



. WAVES IN THIS 



i AREA. 



ARENA COVE 



CONVERGENCE OF ORTHO- 

 GONALS PRODUCES HIGH 

 WAVES IN THIS AREA 



— —- — DEPTH CONTOURS 

 IN FATHOMS 

 12 SECOND PERIOD 



10,000 FT. 

 SCALE 



REFRACTION DIAGRAM 



structures, the location of which was the pur- 

 pose of the survey. 



regional magnetism — In terrestrial magnetism, 

 that part of the observed magnetic field that is 

 attributed to the earth's magnetic field or to 

 effects which are too deep, too broad, or too great 

 in relief to be possible expressions of structure 

 or other features of interest. 



regolith — (or mantle, rock, saproUth). The sur- 

 face layer of sediment, rock waste, alluvium, 

 volcanic ash, glacial drift, organic matter and 

 windblown material which lies above bedrock. 



regressive — Applied to bodies of w^ater and sedi- 

 ments deposited therein during withdrawal of 

 the water and/or emergence of the land. (2) 



regressive reef — One of a series of reefs or bio- 

 herms developed close to and generally parallel 

 to the shore as a result of a retreating sea or 

 rising landmass. (2) 



relative biological effectiveness — (abbreviated 

 RBE). A factor which is used to compare the 

 biological effectiveness of absorbed radiation 

 doses (that is, rads) due to different types of 

 ionizing radiation. More specifically, it is the 

 ratio of an absorbed dose of X-rays or gamma 

 rays to the absorbed dose of a certain particulate 

 radiation required to produce an identical bio- 

 logical effect in a particular experimental organ- 



ism or tissue. This ratio is sometimes called 

 the relative biological efficient factor. (70) 



relative current — The current which is a func- 

 tion of the dynamic slope of an isobaric surface 

 and which is determined from an assumed layer 

 of no motion. The current flows along the con- 

 tours of dynamic topography; the surface 

 slopes upward to the right of the current in the 

 Northern Hemisphere and to the left in the 

 Southern Hemisphere. 



relative current speed — The speed determined 

 by the spacing of dynamic contours drawn at 

 equal intervals of dynamic height anomaly; 

 the speed is inversely proportional to the dis- 

 tance between contours. 



relative index of refraction — See index of 

 refraction. 



relative response — The relative response of a 

 transducer, in decibels, is the amount by which 

 the response under some particular condition 

 exceeds the resijonse under a reference condition 

 that should be stated explicitly. (69) 



relaxation time — In general, the time interval re- 

 quired for a system exposed to some discontinu- 

 ous change of environment to under the fraction 

 {l-e~'), or about 63 percent, of the total change 

 of state which it would exhibit after an indefi- 

 nitely long time. 



134 



