EULERIAN CURRENT MEASUREMENT 



mergence or drowning of the lower portion of a 

 nonglaciated river valley and containing a 

 measurable quantity of sea salt. See inverse 

 estuary, neutral estuary, positive estuary, 

 sound (sense 2), slightly stratified estuary, 

 vertically mixed estuary, highly stratified 

 estuary. 



Eulerian current measurement — Direct observa- 

 tion of the current speed and/or direction during 

 a period of time as it flows past a recording 

 instrument such as the Ekman or Eoberts cur- 

 rent meter. See Lagrangian current measure- 

 ment. 



eulittoral — According to some authorities a zone 

 extending from the high tide level to a depth of 

 about 130 to 195 feet (40 to 60 meters) . (54) 



euphausiid — One of an order (Euphausiacea) of 

 shrimplike, planktonic crustaceans, widely dis- 

 tributed in oceanic and coastal waters, and es- 

 pecially abundant in colder waters. Euphausi- 

 ids grow to 3 to 4 inches in length, and nearly 

 all possess luminous organs. Many of the species 

 engage in typical diurnal vertical migration 

 and may contribute to midwater sound scatter- 

 ing. Some are present near the sea surface at 

 least during certain periods of the year, where 

 they form the principal food for many of the 

 baleen (whalebone) whales. <S'eekrill. 



euphotic zone — The layer of a body of water 

 which receives ample sunlight for the photo- 

 synthetic processes of plants. The depth of this 

 layer varies with the water's extinction coeffici- 

 ent, the angle of incidence of the sunlight, length 

 of day, and cloudiness ; but it is usually 260 feet 

 (80 meters) or more. The compensation depth 

 is the lower boundary of the euphotic zone. ( 5 ) 



euryhaline — Normally inhabiting salt water, but 

 adaptable to a wide range of salinity. ( 58 ) 



eurythermic — Tolerant of a wide range of tem- 

 perature. (58) 



eustatic — Pertaining to a simultaneous, world- 

 wide change in sea level such as from melting of 

 continental glaciers, but not a relative change 

 in level resulting from local coastal subsidence 

 or elevation. (2) 



eutrophic — Pertaining to bodies of water contain- 

 ing abundant nutrient matter. 



euxinic deposition — Deposition in a nearly iso- 

 lated sea basin where for lack of circulation 

 and mixing, the deep waters are deficient in oxy- 

 gen and toxic to all life, but anaerobic bacteria 

 and hydrogen sulfide muds rich in organic mat- 

 ter are produced. Examples are the Black Sea, 

 Carioco Basin, and some fiords. 



evaporation — (also called vaporization). The 

 physical process by which a liquid or solid is 

 transformed to the gaseous state; the opposite 

 of condensation. 



Energy is lost by an evaporating liquid ; and 

 when no heat is added externally the liquid al- 

 ways cools. The heat thus moved is termed the 

 latent heat of vaporization. (5) 



evaporite — One of the sediments which are de- 

 posited from aqueous solution as a result of ex- 

 tensive or total evaporation of the solvent. (2) 



Ewing corer — A piston-type coring device used 

 to obtain 214-inch diameter core samples. The 

 sampler consists of a weight stand on which re- 

 movable weights ca:n be placed, a core barrel 

 (generally of 20-foot length) , a core cutter, and 

 a core catcher. 



expendable bathythermograph — See airborne 

 expendable bathythermograph, shipborne ex- 

 pendable bathythermograph. 



explosives anchorage — See anchorage, 



exposed anchorage — See anchorage. 



exposure — See outcrop. 



extinction coefficient — A measure of the space 

 rate of diminution, or extinction, of any trans- 

 mitted light; thus, it is the attenuation co- 

 efficient applied to visible radiation. 



In oceanography, it is a measure of the attenu- 

 ation of downward-directed radiation in the 

 sea. (5) 



extracellular bioluminescence — Light produc- 

 tion outside the organism resulting from the 

 secretion of photogenic material from special 

 secretory glands. Cypridina, an ostracod, 

 extrudes yellow granules of luciferin and small 

 colorless granules of luciferase into the sea 

 water. These granules dissolve and react to pro- 

 duce light. The deep sea squid, Heterotevihis 

 dispar, emits a luminous cloud much like other 

 squid emit an ink cloud. See photogenic 

 granules. 



extrapolation — The extension of a relationship be- 

 tween two or more variables beyond the range 

 covered by knowledge, or the calculation of a 

 value outside that range. ( 5 ) 



extratropical cyclone — (sometimes called extra- 

 tropical low, extratropical storm) . Any cyclon- 

 ic-scale storm that is not a tropical cyclone, 

 usually referring only to the migratory frontal 

 cyclones of middle and high latitudes. (5) 



extratropical low — See extratropical cyclone. 



extratropical storm — See extratropical cyclone. 



extrusive rocks — Igneous material which has 

 forced its way through other rocks and flowed 

 out upon the surface of the earth or the sea bot- 

 tom before solidifying. The material may 

 emerge as volcanic ash or as lava flows from 

 fissures or cones. See eruptive rocks. (48) 



eye — In meteorology, usually the "eye of the 

 storm" (hurricane, typhoon) ; that is, the 

 roughly circular area of comparatively light 

 winds and fair weather found at the center of a 

 severe tropical cyclone. The winds are gen- 

 erally 10 knots or less; no rain occurs; some- 

 times blue sky may be seen. Eye diameters vary 

 from 4 miles to more than 40 miles; common 

 magnitudes seem to be 12 to 25 miles. Modern 

 observations indicate that the eye does not re- 

 main in steady state but is continuously under- 

 going changes in shape and size. ( 5 ) 



60 



