VOLUME SCATTERING FUNCTION 



veering — 1. According to general international 

 usage, a change in wind direction in a clockwise 

 sense (for example, south to southwest to west) 

 in either hemisphere of the eartli ; the opposite 

 of backing. 



2. According to widespread usage among 

 United States meteorologists, a change in wind 

 direction in a clockwise sense in the Northern 

 Hemisphere, counterclockwise in the Southern 

 Hemisphere ; the opposite of backing. 



vein — A narrow lead or lane in pack ice. (59) 



veliger — The planktonic larval second stage of 

 many gastropods. 



velocity discontinuity — An abrupt change of the 

 rate of propagation of seismic waves within the 

 earth, as at an interface. (35) 



velocity hydrophone — A hydrophone in which 

 the electric output substantially corresponds to 

 the instantaneous particle velocity in the im- 

 pressed sound wave. (69) 



velocity of sound — See sound velocity. 



veneer — A thin layer of sediment covering a rocky 

 surface. 



venomous marine animal — Any of various orga- 

 nisms living in the sea that are capable of in- 

 jecting venom into other organisms, either to 

 capture prey or in self-defense. This capability 

 is developed to the highest degree in some of the 

 jellyfishes, sea urchins, marine snails of the genus 

 OoTius, stingrays, catfishes, scorpionfishes, and 

 sea snakes. 



ventral — Pertaining to or situated on the lower 

 or abdominal surface ; opposite of dorsal. (26) 



vertex velocity — The velocity at which a sound 

 ray becomes horizontal (grazing angle equals 

 zero) . 



vertical haul — (or vertical toio). The lifting of 

 an open plankton net from a certain depth to 

 the surface while the ship or other platform is 

 on station. See horizontal haul, oblique haul. 



vertical intensity — The magnetic intensity of the 

 vertical component of the eartli's magnetic field, 

 reckoned positive if downward, negative if 

 upward. 



vertically mixed estuary — An estuary in which 

 the salinity is homogeneous with depth but in- 

 creases along its length from the head to the 

 mouth. 



vertical tow — See vertical haul. 



very close drift ice — See very close pack ice. 



very close pack ice — Sea ice whose concentration 

 is practically 10-tenths (8-eighths) with little 

 if any open water. (74) 



very open drift ice — See very open pack ice. 



very open pack ice — Sea ice whose concentration 

 ranges between 1- and ^-tenths (1- to 2-eighths) . 

 (74) 



very shallow water — Water of depths less than 

 1^5 the wavelength of surface waves. 



very shallow water wave — See shallow water 

 wave. 



vesicle — See pneumatocyst. 



vigia — A rock or shoal in the sea, whose existence 

 or position is doubtful ; also a warning note to 

 this effect on a nautical chart. (68) 



viscosity — (or internal friction) . That molecular 

 property of a fluid whicli enables it to support 

 tangential stresses for a finite time and thus to 

 resist deformation. (5) 



viscous damping — The dissipation of energy that 

 occurs when a particle in a vibrating system is 

 resisted by a force whose magnitude is a con- 

 stant independent of displacement and velocity, 

 and whose direction is opposite to the direction 

 of the velocity of the particle. (6) 



viscous stress — The resistive force of the water; 

 it is proportional to the speed of the current but 

 acts opposite to its direction of flow. 



V„ — The volume of mercury below the 0°C mark 

 determined at 0°C in the reversed main ther- 

 mometer. Expressed in degrees Celsius. Vo is 

 found on the deep sea reversing thermometer 

 card. (67) 



voe — An inlet, bay, or creek. (2) 



void ratio — The ratio of intergranular voids to 

 the volume of solid material in a sediment. (2) 



volcanic ash — Uncemented pyroclastic material 

 consisting of fragments mostly under 4 milli- 

 meters in diameter. Coarse ash is i^ to 4 milli- 

 meters in grain size; fine ash is below i^ milli- 

 meter. A constituent of some marine sediments. 

 (2) _ 



volcanic blocks — Essential, accessory, or acci- 

 dental volcanic ejecta, usually angidar and 

 larger than 32 millimeters in diameter, erupted 

 in a solid state. (2) 



volcanic bombs — Fragments or lava up to several 

 feet long thrown out of a volcano in a liquid, 

 semifluid, or plastic state and solidified in flight 

 or soon after landing. 



volcanic breccia — A rock composed predomi- 

 nantly of angular volcanic fragments greater 

 than 2 millimeters in size set in a subordinate 

 matrix of any composition and texture, or with 

 no matrix ; or composed of fragments other than 

 volcanic set in a volcanic matrix. (17) 



volcanic cinders — See scoria. 



volcanic cone — A conical hill or mountain with a 

 crater or cup-shaped hollow at the summit con- 

 structed of ash, scoria, lava, and other volcanic 

 materials discharged through the summit crater. 

 [See figure for compound volcano.) 



volcanic ejecta — See tephra. 



volcanic eruption — The emission or ejection of 

 volcanic material at the earth's surface from a 

 crater or from a fissure. (2) 



volcanic harbor — A bay formed by the flooding 

 of a volcanic crater through a gap in the rim. 



volume reverberation — See reverberation. 



volume scattering function — See scattering 

 function. 



175 



