MEDIAN DIAMETER. The diameter which marks the division of a given sand sample 

 into two equal parts by weight, one part containing all grains larger than 

 that diameter and the other part containing all grains smaller. 



MEGARIPPLE. See SAND WAVE. 



MIDDLE-GROUND SHOAL. A shoal formed by ebb and flood tides in the middle of 

 the channel of the lagoon or estuary end of an inlet. 



MINIMUM DURATION. See DURATION, MINIMUM. 



MINIMUM FETCH. The least distance in which steady-state wave conditions will 

 develop for a wind of given speed blowing a given duration of time. 



MIXED TIDE. A type of tide in which the presence of a diurnal wave is 

 conspicuous by a large inequality in either the high or low water heights, 

 with two high waters and two low waters usually occurring each tidal 

 day. In strictness, all tides are mixed, but the name is usually applied 

 without definite limits to the tide intermediate to those predominantly 

 semidiurnal and those predominantly diurnal. (See Figure A-10.) 



MOLE. In coastal terminology, a massive land-connected, solid-fill structure 

 of earth (generally revetted), masonry, or large stone, which may serve as 

 a breakwater or pier. 



MONOCHROMATIC WAVES. A series of waves generated in a laboratory; each wave 

 has the same length and period. 



MONOLITHIC. Like a single stone or block. In coastal structures, the type of 

 construction in which the structure's component parts are bound together 

 to act as one. 



MUD. A fluid-to-plastic mixture of finely divided particles of solid material 

 and water. 



NAUTICAL MILE. The length of a minute of arc, 1/21,600 of an average great 

 circle of the Earth. Generally one minute of latitude is considered equal 

 to one nautical mile. The accepted United States value as of 1 July 1959 

 is 1,852 meters (6,076.115 feet), approximately 1.15 times as long as the 

 U.S. statute mile of 5,280 feet. Also geographical mile. 



NEAP TIDE. A tide occurring near the time of quadrature of the moon with the 

 sun. The neap tidal range is usually 10 to 30 percent less than the mean 

 tidal range. 



NEARSHORE (zone). In beach terminology an indefinite zone extending seaward 

 from the shoreline well beyond the breaker zone. It defines the area of 

 NEARSHORE CURRENTS. (See Figure A-1.) 



NEARSHORE CIRCULATION. The ocean circulation pattern composed of the 

 CURRENTS, NEARSHORE and CURRENTS, COASTAL. See CURRENT. 



A-22 



