RISE, TIDAL - The height of tide as referred to the datum of a chart. 



ROADSTEAD - (Nautical) A sheltered area of water near shore where vessels 

 may anchor in relative safety. Also RUADo 



ROCK - (l) (Engineering) A natural aggregate of mineral particles 



connected by strong and permanent cohesive forces. In igneous and 

 metaraorphic rocks^ it consists of interlocking crystals; in sedimentary 

 rocks, of closely packed mineral grains, often bound together by a 

 natural cement. Since the terms "strong" and "permanent" are 

 subject to different interpretations, the boundary between rock 

 and soil is necessarily an arbitrary one„ (2) (Geological) The 

 material that forms the essential part of the earth's solid crust, 

 and includes loose incoherent masses, such as a bed of sand, gravel, 

 clay or volcanic ash, as x^iell as the very firm, hard, and solid 

 masses of granite, sandstone, limestone, etc. Most rocks are 

 aggregates of one or more minerals, but some are composed entirely 

 of glassy matter, or of a mixture of glass and minerals. 



ROLLER - An indefinite term, sometimes considered to be one of a series 

 of long-crested, large waves which roll in upon a coast, as after 

 a storm. 



RUBBLE - (l) Loose angular water-worn stones along a beach, (2) Rough, 

 irregular fragments of broken rock. 



RUUNEL - A corrugation (trough) of the foreshore (or the bottom just 

 offshore), formed by wave. and/or tidal action. Larger than the 

 trough between ripple marks, 



RUN-UP - The rush of water up a structure on the breaking of a wave. 

 Also UPRUSH. The amount of run-up is the vertical height above 

 still water level that the rush of water reaches, 



SALT MARSH - A marsh periodically flooded ty salt water., 



SAM) - See SOIL CLASSIFICATION . 



SAND BAR - (l) See BAR. (2) In a river, a ridge of sand built up to or 

 near the surface by river currents. 



SANT) REEF - Synonymous with BAR. 



SCARP - A more or less continuous line of cliffs or steep slopes facing 

 in one general direction which are caused by erosion or faulting. 



Also escarpi#;nt. 



SCARP, BEACH - An almost vertical slope along the beach caused by erosion 

 by wave action. It may vary in height from a few inches to several 

 feet, depending on wave action and the nature and composition of the 

 beach. 



A-27 



