English

ROCKS formed by the accumulation of SEDIMENT in water (aqueous DEPOSITS) or from air (eoli­an DEPOSITS). The SEDIMENTS may consist of rock frag­ments or particles of various sizes (conglomerate, sandstone, shale); of the remains or products of ani­mals or plants (certain LIMESTONES and coal); of the product of chemical action or of evaporation (salt, gypsum, etc.); or of mixture of these materials.

The process of breakup and separation of particles from the parent ROCK, their transportati­on, deposition, and consolidation into another ROCK.

A STANDING WAVE oscillation of an enclosed or semi-enclosed water body that continues, pendulum fashion, after the cessation of the originating force, which may have been either seismic, atmospheric, or wave induced.

The study of the shallower internal structure of the earth by generating acoustic waves and registering their reflection from subsurface layers.

The study of the shallower internal structure of the earth by generating acoustic waves and registering their return at increasing distances from the acoustic source, thus detecting waves that have been transmitted along deeper layers of greater elasticity and rigidity.

The degree of decrease in the RESPONSE of a resonant device with depar­ture from RESONANCE. Selec­tivity determines the ability of a RADIO RECEIVER to differentiate between SIGNALS of different carrier FREQUENCY.

Half the angle at the observer subtended by the visible disk of a CELESTIAL BODY. SEXTANT ALTI­TUDES of the SUN and MOON should be corrected for semidiameter unless the centre is observed, as with a BUBBLE SEXTANT.

A CORRECTION due to SEMI­DIAMETER, particularly that sextant altitude correc­tion resulting from OBSERVATION of the upper or lower LIMB of a CELESTIAL BODY, rather than the centre of that body.