DISTRIBUTION 



dilution — The reduction in the concentration of 

 dissolved or suspended substances by mixing 

 witli water of a lower concentration. 



diluvium — A general term for all glacial and 

 fluvio-glacial deposits of continental glaciation. 



(2) 



dinoflagellate— One of a class (Dinophyceae) 

 of single-celled microscopic or minute organ- 

 isms. Dinoflagellates may possess both plant 

 (chlorophyll and cellulose plates) and animal 

 (ingestion of food) characteristics. Many 

 marine forms are luminescent and, when in great 

 numbers, are responsible for sheet-type lumi- 

 nescence. In addition, dense concentrations 

 may create a red discoloration, (red tide) and 

 cause mass mortality of marine life. Other 

 discolorations due to these organisms may be 

 yellow, green, or shades of brown, but the ma- 

 jority of these concentrations are nontoxic to 

 marine life. 



dip — 1. The angle at which the rock structure is 

 inclined with a horizontal plane. 



2. The angle formed by the lines of total mag- 

 netic force and the horizontal plane at the earth's 

 surface; reckoned positive if downward. See 

 inclination. 



3. The increase in depth of a moored mine case 

 (or buoy), due to current force against the case 

 and cable. 



dip equator — See magnetic equator. 



dipolar spreading — See spreading of sound. 



directional hydrophone — A hydrophone the re- 

 sponse of which varies significantly with the di- 

 rection of sound incidence. ( 69 ) 



direction response pattern — (or ieam pat- 

 tern). The directional response pattern of a 

 transducer used for sound emission or recep- 

 tion is a description, usually presented graph- 

 ically, of the response of the transducer as a 

 function of the direction of the transmitted or 

 incident sound waves in a specified plane and at a 

 specified frequency. In general, the beam pat- 

 tern will change with a change in the operating 

 frequency. (3) 



directional spectrum — The spectral distribution 

 of wave energy by both frequency and direc- 

 tion. 



directivity — The confining of sound to a beam by 

 mechanical and/or electronic means. 



directivity index — A measure of sound pressure 

 level in one direction compared to that in all 

 other directions. 



direct path — See surface path. 



direct tide — A gravitational solar or lunar tide 

 in the ocean which is in phase with the apparent 

 motions of the attracting body, and consequently 

 has its local maximums directly under the tide- 

 producing body, on the opposite side of the 

 earth. ^Vee reversed tide. (5) 



discharge — The rate of flow of water or ice from 

 a river, fiord, or harbor at a given instant in 



terms of volume per unit time, for example, 

 cubic feet per second. 



discolored water — Sea water having a color other 

 than the blues and greens normally seen. Varia- 

 tions of the colors red, yellow, green, and brown, 

 as well as black and white, have been reported. 

 Discolorations may appear in patches, streaks, or 

 large areas and may be caused by concentrations 

 of inorganic or organic particles or plankton. 

 See red tide. 



discontinuity — The abrupt variation or jump of a 

 variable at a line or surface. See interface. 



(5) 



discontinuity layer — See thermocline, pyc- 

 nocline. 



disintegration — (also called decay., rot., crumble) . 

 A break down or decomposition of ice concen- 

 trations or complete disappearance thereof. See 

 radioactive decay. 



dislocation — (or displacement). Used in a gen- 

 eral" sense to refer to relative movements of rocks 

 along a fault. 



dispersion — 1. The separation of a complex sur- 

 face gravity wave disturbance into its com- 

 ponent parts. (73) 

 2. See acoustic dispersion. 



disphotic zone — The dimly lighted zone extend- 

 ing from about 250 to 650 or more feet. Little 

 plant production can take place in this zone, 

 and the plants found here have mostly sunk from 

 the layer above. See aphotic zone, euphotic 

 zone. (54) 



displacement — See dislocation. 



displacement volume — The volume of fluid dis- 

 placed by plankton which has been drained of 

 water and which is a measure of the planktonic 

 biomass. 



displacement weight— -See displacement vol- 

 ume. 



display — See bioluminescent display. 



dissected — Cut by erosion into hills, ridges, 

 valleys, etc. May be applied to a submarine 

 shelf or slope cut into by submarine canyons or 

 sea valleys. 



dissipation — In thermodynamics, the conversion 

 of kinetic energy into heat by work done against 

 the viscous stresses. Sometimes the rate of 

 conversion per unit volume is meant. 



distilled water — See pure water. 



distortion — An undesired change in waveform. 

 Noise and certain desired changes in waveform, 

 such as those resulting from modulation or de- 

 tection, are not usually classed as distortion. 



(6) 



distortional wave — See transverse wave. 



distribution — Arrangement in time or space, as 

 the distribution of temperature; or apportion- 

 ment among various classes, or class intervals, 

 especially ranges of values of a certain variable. 

 (5) 



49 



