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Labrador Current — A current that flows south- 

 ward from Baffin Bay, through the Davis Strait, 

 and southeastward along the Labrador and New- 

 foundland coasts. East of the Grand Banks of 

 Newfoundland the Labrador Current meets the 

 Gulf Stream, and the two flow eastward as the 

 North Atlantic Current. 



LaCoste-Romberg (zero length spring) gravi- 

 meter — A long-period vertical seismograph su- 

 spended system adapted to the measurement of 

 gravity differences. 



LaFond's Tables— A set of tables and associated 

 information for correcting reversing thermom- 

 eters and computing dynamic height 

 anomalies, compiled by E. C. LaFond and pub- 

 lished bv the U.S. Naval Oceanographic Office 

 as H.O. Publication 614. 



lagan — See jettison. 



lag coefficient — See time constant. 



lagging of the tide— (also called daily retarda- 

 tion^ retardation) . The periodic retardation in 

 the time of occurrence of high and low water 

 due to changes in the relative positions of the 

 moon and the sun. The opposite effect is called 

 priming of the tides. 



lag gravel — Kesidual accumulations of coarse 

 particles from which the fine material has been 

 winnowed by currents unable to move the coarse 

 material. 



lagoon — A shallow sound, pond, or lake generally 

 separated from the open sea. {See figures for 

 atoll and coral reef.) 



lagoon beach — The lagoonward facing beach of 

 reef islands. (56) See figiire for atoll.) 



lagoon channel — Properly refers to a naviga- 

 tional channel or pass through a reef and into 

 and through the lagoon. It has been applied 

 to the lagoon itself. {See figure for coral reef.) 



lagoon cycle — The time required and sequence of 

 events involved in the filling of a lagoon by 

 sediments followed by their erosion by wave 

 action and eventual refilling by deposition. 



lagoon floor — The undulating to nearly level floor 

 of the lagoon. (56) {See figure for atoll.) 



lagoon reef margin — The lagoonward margin of 

 the reef or island in an atoll. (56) (/S'ee figure 

 for atoll.) 



lagoon slope — The border zone of the lagoon that 

 slopes downward from the lagoon reef margin 

 or lagoon beach to the lagoon floor. (56) 

 {See figure for atoll.) 



Lagrangian current measurement — Direct ob- 

 servation of the current speed and/or direction 

 by a recording device such as a parachute 

 drogue, which follows the movement of a water 

 mass through the ocean. See Eulerian current 

 measurement. (73) 



laguna — A shallow coastal sound, channel, or lake 

 connected with the sea. (48) 



Lambert conformal conic projection — A con- 

 formal projection in which all materials are 

 represented by straight lines that meet in a com- 

 mon point beyond the limits of the map, and 

 the parallels, are concentric circles whose center 

 is at the point of intersection of the meridians. 

 Meridians and parallels intersect in right angles, 

 and angles on the earth are correctly represented 

 on the projection. This projection may have 

 one standard parallel along which the scale is 

 held exact; or there may be two such standard 

 parallels, both maintaining exact scale. (37) 



Lambert's formula — A formula for computing 

 the mean wind direction from a series of observa- 

 tions. It mayJbe written : " 

 _ E— [WiNE + SE— NW— SW) cos 45°] 

 tana N— [S<NE-f NW-^SE— SW) cos 4_51L 

 where « is the Tneaii wind direction, and each 

 point of the compass replaced by the number of 

 observations of wind from that direction. (5) 



lamellibranch — See bivalve. 



lamina — 1. A sediment or sedimentary rock layer 

 less than one centimeter thick visually separable 

 from the material above and below. Lamina- 

 tion refers to the alternation of such layers 

 which differ in grain size or composition. (2) 

 2. (or hlade, frond). The expanded and/or 

 elongate portion of the thallus of an alga. 



laminar flow — (also called sheet floiu, streamline 

 floit} ) . A flow in which the fluid moves smooth- 

 ly in streamlines in parallel layers or sheets; a 

 nonturbulent flow. See turbulent flow. (5) 



lamination — See lamina. 



lamp shell — See brachiopod. 



land and sea breeze — The combination of a land 

 breeze and a sea breeze as a diurnal 

 phenomenon. (61) 



land breeze — A light wind blowing from the land 

 caused by unequal cooling of land and water 

 masses. (61) 



land fast ice — See fast ice. 



land floe — An unusually thick fragment of fast 

 ice which has become detached from the parent 

 formation and is afloat. (59) 



94 



