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.
Puerto Rico Trough the deepest spot in the Atlantic and the second deepest in all the oceans, 30,246 feet or 9,219 meters.
red tide a bloom of phytoplankton that colors the water red and releases powerful toxins that kill large masses of fish and other sea life; the toxin released by some phytoplankton accumulates in mussels and clams and often proves fatal to humans who eat these shellfish.
ring a meander that has broken off from the main current.
sapropel black organic ooze or sludge, the source material for petroleum and natural gas, found in great accumulations under the ocean.
Sargasso Sea not actually a sea in itself but a section of the North Atlantic (a section the size of the continental U.S.) between the West Indies and the Azores, noted for its small, floating meadows of seaweed.
Sargasso weed the free-floating seaweed, known for its centuries-long life span, that occupies the Sargasso Sea.
sea elements the elements that make up the sea, primarily (96.5 percent) oxygen and hydrogen, followed in order of prevalence by chlorine, sodium, magnesium, sulfur calcium, potassium, bromine, carbon, strontium, boron, silicon, and others.
seafloor spreading the expanding of the seafloor along mid-ocean ridges, forming new crust.
sea high an abyssal hill.
seamount a submarine mountain over 700 meters in elevation.
seamount chain a series of seamounts.
seascarp a long, high cliff or wall, often part of a fracture zone.
seaway a sea route taken by vessels.
seiche a wave that oscillates from a few minutes to a few hours, due to either seismic or atmospheric disturbances.
shoal a shallow area, a hazard to navigation.
sill the ridge or saddle between two basins, troughs, or trenches.
slick a patch of smooth surface water surrounded by rippled water, the result of internal wave flow but often mistaken for an effect of wind action.
sounding measurement of the depth of water.
spiller a wave with a concave back and a crest that breaks gradually and continuously, usually found offshore.
spindrift sea spray.
spring tide the very high tide occurring at new and full Moon and reinforced by the gravitational pull of the Sun.
submarine bar an underwater sandbar.
submarine fan a large, offshore deposit of sediment, sometimes stretching for hundreds of miles and fanning out into the shape of a cone or apron, originating from the mouth of a large river. Also known as a submarine delta or submarine apron.
submarine spring a freshwater spring upwelling from the seafloor.
terrace a steplike section of the seafloor.
Tethys Sea one of the names for the huge, universal sea that hypothetically surrounded the superconti- nent of Pangaea before it divided. Also known as Panthalassa.
thalassic pertaining to the oceans.
thalassophobia the fear of the ocean.
tidal bore a high, dangerous wave caused by a surging incoming tide upstream in a narrowing estuary or by the collision of tidal currents. Also known as an eagre.
trench a steep-sided, narrow depression in the seafloor.
trough same as a trench but gently sided.
tsunami a seismic sea wave, caused by an earthquake, frequently large and dangerous. Erroneously referred to as a tidal wave.
turbidity current an avalanche of sediment-laden water, moving as fast as 50 miles per hour down a continental slope into deeper water and stirring up silt; known to gouge out channels in the seafloor.