Descriptionary

dead water a body of water, particularly common in the fjords and seas of Scandinavia, that mysteri­ously slows or nearly stops the forward progress of ships; thought to be caused by a thin layer of fresh­water floating above a layer of denser, salty water that, when mixed, creates a train of slow-moving, submerged waves that exert a powerful drag on ves­sels passing over it.

deep a deep-sea plain within a large basin.

deep-scattering layer a large body of free-swimming sea organisms, such as fish or squid, that confuses sonar readings by creating a "false bottom" or false seafloor.

doldrums equatorial ocean regions characterized by flat, calm seas and little or no wind.

Douglass sea and swell scale a scale of numbers assigned to descriptive terms (0 = calm, 8 = precipi­tous, 9 = confused, etc.) to denote the sea's state with a second scale of numbers (0 to 99) to denote low to heavy swells.

eddy a swirling current running contrary to the main current; may be caused by two currents meeting head-on or side-long.

El Nino a colloquial Spanish term for the Christ child now applied to a warm current of ocean water that moves into the coastal waters of Peru around Christmastime; the warm waters smother an upwell- ing of cold water normally in place here with disas­trous effects on sea life and worldwide wind and weather patterns.

Emperor Seamounts the largest chain of submarine mountains in the Pacific; links with the Hawaiian Seamounts.

eustatic change a worldwide change of sea level produced by an increase or decrease in the amount of seawater.

fathom a measurement of sea depth; 1 fathom equals 6 feet.

fathometer a sonic depth finder.

fetch the distance wind travels from one point on the sea to another and its relation to the size of waves created; the longer the fetch, the bigger the waves.

fracture zone an area of submarine fractures in the Earth's crust, marked by troughs, ridges, and mountains.

Graveyard of the Atlantic approximately 220 miles southeast of Cape Hatteras, North Carolina, a site of strong local currents and storms with a powerful undercurrent running underneath the Gulf Stream, the combined causes of thousands of shipwrecks here.

graybeards choppy, frothy waves.

Gulf Stream a warm ocean current originating in the Gulf of Mexico and flowing east around Florida, up the southeast coast of the United States, then east again to the North Atlantic Current.

guyot a flat-topped mountain under the sea.

gyre the circular path followed by oceanwide currents.

hadal zone the deepest layer of ocean water and all its fauna, starting from 6,000 meters down; usu­ally within a trench. Also known as the ultra-abyssal zone.

hole a sinkhole or vertical chimney in the seafloor.

hydrography the study of the sea to determine its use for navigation.

ichthyology the study of fish.

internal wave a submerged or underwater wave, often invisible from the surface.

island-arc deeps deep-sea trenches bordering some continents; some reach depths of 9,000 meters.

meander a bend or bulge in an ocean current that breaks off, forms an eddy, and moves off indepen­dently of the current that spawned it.

Mid-Atlantic Ridge originally called the Dolphin Rise, after the ship that discovered it, a long chain of mountains under the mid-Atlantic stretching from Iceland to Antarctica.

nautical mile 6,080.2 feet.

neap tide the minimal or low-moving tide occurring after the first and third quarters of the Moon, when the Sun's tidal force acts at right angles to that of the Moon.

nekton collective term for all free-swimming sea creatures, such as fish, squid, or whales.

North Atlantic gyre the large, rotating current of the North Atlantic. There is also the South Atlantic gyre.

North Pacific gyre the large, rotating current of the North Pacific. There is also the South Pacific gyre.

ocean acoustic tomography the scientific technique of using sound transmitters and receivers to map such underwater properties as currents and eddies.

oceanography the study of the oceans.

Panthalassa the huge, hypothetical universal ocean surrounding the hypothetical supercontinent of Pangaea before it divided. Also known as the Tethys Sea.

pelagic region the open ocean waters, as opposed to the ocean floor.

phytoplankton the microscopic ocean plants living on or near the surface, the bottom of the sea's food chain.

plunger a wave with a convex back and a crest that falls suddenly and violently, usually found on or near shore.

province any region of the seafloor united by a common feature.