GRADED SHORELINE 



uniform distribution of particles from coarse to 

 fine. (2) 



graded shoreline — A shoreline that has been 

 straightened by the building of bars across 

 embayments and by the cutting back of head- 

 lands. (2) 



grade scale — A subdivision of an essentially con- 

 tinuous scale of particle size into a series of 

 size classes. (2) See Atterberg grade scale, 

 phi grade scale, Tyler standard grade scale, 

 Udden grade scale, Wentworth grade scale. 



gradient — The rate of decrease of one quantity 

 with respect to another, for example, the rate of 

 decrease of temperature with depth. See 

 ascendant. 



gradient current — A current defined by assuming 

 that the horizontal pressure gradient in the sea 

 is balanced by the sum of the coriolis and bot- 

 tom frictional forces. At some distance from 

 the bottom the effect of friction becomes negligi- 

 ble, and above this the gradient and geostrophic 

 currents are equivalent. 



graduation — See curve fitting. 



Graf sea gravimeter — A balance-type gravity 

 meter (heavily overdamped to attenuate ship- 

 board vertical accelerations) which consists of a 

 mass at the end of a horizontal arm that is sup- 

 ported by a torsion spring rotational axis. The 

 mass rises and falls with gravity variation, but 

 is restored to near its null position by a horizon- 

 tal reading spring, tensioned with a micrometer 

 screw. The difference between actual beam 

 position and null position gives indication of 

 gravity value after the micrometer screw posi- 

 tion has been taken into account . ( 35 ) 



grail — Coarse or medium sized sediment particles, 

 that is, gravel or sand. 



grains — (or particle). The individual particles 

 which form a sediment which range in size from 

 smaller than 0.0039 millimeter (clay particles) 

 to larger than 256.0 millimeters (boulders). 

 See phi grade scale. 



gram — A cgs unit of mass; originally defined as 

 the mass of 1 cubic centimeter of water at 4°C; 

 but now taken as the one-thousandth part of the 

 standard kilogram, a mass preserved by the 

 Intefnational Bureau of Weights and Measures 

 at Sevres, France. (5) 



gram atom — See gram atomic weight. 



gram atomic weight — The mass of an element in 

 grams, numerically equal to its atomic weight. 

 Thus, the gram atomic weight of carbon is 12 

 grams (one gram atom of carbon weighs 12 

 grams). 



Dissolved elements in a unit volume of sea 

 water are usually measured in milligram (or 

 microgram) atoms per liter. 



gram calorie — See calorie. 



gram mole — See gram molecular weight. 



gram molecular weight— The mass of a molecule 

 in grams, numerically equal to its molecular 



weight. Thus, the gram molecular weight of 

 molecular oxygen is 32 grams (one mole of 

 0, weighs 32 grams). 



granite — A crystalline plutonic rock consisting es- 

 sentially of alkali feldspar and quartz. In seis- 

 mology, a rock in which the compressional wave 

 velocity varies approximately between 5.5 and 

 6.2 kilometers per second. Granitic is a textural 

 term applied to coarse and medium-grained 

 granular igneous rocks. (2) 



granitic — See granite. 



granular ice — Ice composed of many tiny, opaque, 

 white or milky pellets or grains frozen together 

 and presenting a rough surface. This is the 

 type of ice deposited as rime and compacted as 

 neve. (68) 



granule — Eock fragments of overall gravel size 

 larger than very coarse sand (2.0 millimeters) 

 but smaller than pebbles (4.0 millimeters) . See 

 phi grade scale. 



granulometric facies — Cumulative curves rep- 

 resenting sedimentary grain size analyses; sub- 

 divided into linear, parabolic, logarithmic, and 

 hyperbolic facies depending upon the shape of 

 the curve. (2) 



grapestone — A cluster of small calcareous pellets, 

 resembling grapes, stuck together by incipient 

 cementation shortly after deposition. (2) 



grass — See seagrass. 



graticule — The network of lines representing 

 parallels and meridians on a map, chart, or plot- 

 ting sheet. (68) 



gravel — Loose detrital material ranging in size 

 from 2 to 256 millimeters. See stone, phi 

 grade scale. 



gravimeter — A weighing device or instrument of 

 sufficient sensitivity to register variations in the 

 weight of a constant mass when the mass is 

 moved from place to place on the earth and 

 thereby subjected to the influence of gravity at 

 those places. 



Gravimeters are employed in determining dif- 

 ferences in the intensity of gravity between an 

 initial or base station at which the value of 

 gravity is known or assumed and at nearby 

 points for which values of gravity are desired. 

 Gravimeters are also termed gravity meters. 



gravitation — In general, the mutual attraction be- 

 tween masses of matter (bodies). In geodesy, 

 the mutual attraction between the earth and 

 bodies on or near its surface. Gravitation is the 

 component of gravity which acts toward the 

 earth. (37) 



gravitational tide — See equilibrium tide. 



gravity — ^That force which tends to pull bodies 



towards the earth : that is, to give bodies weight. 



Gravity is the resultant of two opposing 



forces : gravitation and the centrifugal force 



due to the rotation of the earth. (37) 



72 



