279 GLOSSARY GLOSSARY Upstream valve: A valve that operates against the direction of gas flow. Upwelling: The vertical movement of water in a body of water and the subsequent replacement of that water from beneath. Caused by wind blowing the surface water away from shore. V Valve snorkel: The tube extending from the bottom of a scuba cylinder valve designed to prevent foreign matter from entering the valve when the tank is inverted. Variation: The local difference in degrees between true and magnetic north. Vestibular system: A series of semi-circular canals within the inner ear that provide a person with orientation and a sense of balance. W Wave crest: The highest point of a wave. Wave length: The distance between two successive waves. Wave period: The time required for two consecutive waves to pass a fixed point. Waves: Forms of energy moving in water and caused by the wind. Wave sets: See Surf Beat. Wave trough: The lowest point of a wave. Work: The application of force through a distance. Z Zooplankton: Animal plankton that generally feeds on phytoplankton.
20047TC
To see the actual publication please follow the link above