CORE CUTTER 



only by density differences within the fluid, and 

 forced convection, motion induced by mechan- 

 ical forces such as deflection by a large-scale sur- 

 face irregularity, turbulent flow caused by fric- 

 tion at the boimdary of a fluid, or motion caused 

 by any applied external force. See thermo- 

 haline convection. (5) 



convection cell — See cellular convection. 



convective overturn — In oceanography, same as 

 overturn. (5) 



convergence — (or front). 1. Situation whereby 

 waters of difl'erent origins come together at a 

 point or, more commonly, along a line known 

 as a convergence line. Along such a line the 

 denser water from one side sinks under the 

 lighter water from the other side. The recog- 

 nized convergence lines in the oceans are the 

 polar, subtropical, tropical, and equatorial con- 

 vergence lines. Regions of convergence are also 

 referred to as convergence zones. (25) 



2. In refraction phenomena, the decreasing 

 of the distance between orthogonals in the di- 

 rection of wave travel. Denotes an area of in- 

 creasing wave height and energy concentration. 

 (61) 



convergence zone — 1. See convergence (sense 1) . 

 2. The region in the deep ocean where sound 

 rays, refracted from the depths, arrive at the 

 surface in successive intervals of 30 to 35 nauti- 

 cal miles. The repeated occurrence of these 

 zones to several hundred miles from tlie sound 

 source depends on the refraction of sound rays 

 at depth and the reflection of these rays at the 

 surface. 



convergence zone paths — The velocity structure 

 of permanent deep sound channels which pro- 

 duces focusing regions at distant intervals from 

 a shallow source. 



convoy routing — Methods of providing optimal 

 routes for one or more escorted sliips under given 

 environmental conditions. Routing may be 

 made to provide minimum time routes, mini- 

 mum wave routes, minimum submarine detection 

 routes, etc. 



Copenhagen water — See normal water. 



copepod — One of a subclass (Copepoda) of 

 minute shrimplike crustaceans, most species of 

 which range between about 0.5 and 10.0 milli- 

 meters in length. Many species are biolumi- 

 nescent, and concentrations can prodiice bright 

 sparkling light. Copepods occur in the surface 

 layers of temperate and subpolar waters in large 

 concentrations. 



coprolites — See fecal pellet. 



coquina — (or coquiTwid limestone, hiostroTnal 

 limestone). A coarse-grained porous friable 

 variety of limestone made up chiefly of shell, 

 shell fragments, and coral. (2) 



coquinoid limestone — See coquina. 



coral — 1. The hard calcareous skeleton of various 

 anthrozoans and a few hydrozoans (the mil- 



lepores), or the stony solidified mass of a num- 

 ber of such skeletons. In warm waters colonial 

 coral forms extensive reefs of limestone. In 

 cool or cold water coral usually appears in the 

 form of isolated solitary individuals. Oc- 

 casionally, large reefs formed in cold waters by 

 calcareous algae {Lithothamnion) have been 

 referred to as a coral. (9) 



2. The entire animal; a compound polyp 

 which produces the skeleton. 



coralgal — The carbonate sediment derived from 

 corals and algae. 



coral head — A massive mushroom or pillar- 

 sliaped coral growth. See reef patch. {See 

 figure for atoll.) 



coral knoll — See reef patch. 



coralline — Pertaining to, composed of, or having 

 the structure of corals; as coralline limestone. 

 (2) 



coralline alga— One of a family (Corallinaceae) 

 of red algae having either a bushy or encrusting 

 form and deposits of calcium carbonate either 

 on the branches or as a crust on the substrate. 

 Certain genera of the encrusting forms, Litho- 

 thamnion and Porolithon, develop massive en- 

 crustations on coral reefs. 



coral patch — See encrusting bryozoans. 



coral pillar — See reef patch. 



coral reef — A ridge or mass of limestone built up 

 of detrital material deposited around a frame- 

 work of the skeletal remains of mollusks, 

 colonial coral, and massive calcareous algae. 

 Coral may constitute less than half of the reef 

 material. (55) (/S'ee also figure for atoll.) 



corange line — A line passing through places of 

 equal tide range. (50) 



Cordillera — An entire mountain system, including 

 all the subordinate ranges, interior plateaus and 

 basins. (62) 



core — 1. A vertical, cylindrical sample of the 

 bottom sediments from which the nature and 

 stratification of the bottom may be determined. 

 2. The central zone of the earth {see centre- 

 sphere). Its upper boundary is defined by a 

 seismic discontinuity at 2,900 kilometers 

 (Gutenberg-Wiechert discontinuity). {See fig- 

 ure for earth structure.) 



core barrel — The tubular section of a core sam- 

 pling device. Bottom sediment samples are 

 collected either directly in the core barrel or in 

 a plastic liner placed inside it. Barrel diameter 

 may vary from 1% inches to several inches. 



core catcher — (or core retain-er). Any device in 

 the lower end of a core barrel designed to pre- 

 vent collected bottom sediments from slipping 

 out while the coring device is brought up to the 

 surface. One type consists of an interleaved 

 metal spring device which slips into the lower 

 end of a core barrel. 



core cutter — (or cutting edge). A device which 

 fits over the end of the coring tube and holds the 



39 



